Technical field

The present invention relates to Wi-Fi equipment and in particular to an antenna array suitable for use with a Wi-Fi access point which is capable of accurately spatially locating, for example, individual users of that access point or physical items which have been suitably equipped to interact with that access point. Background

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

A Wi-Fi access point consists of one or more transmit channels, for sending digital information to an item of user equipment (UE) and one or more receive channels for receiving digital information from a UE. Items of user equipment can include: mobile telephony devices, tablet computers, 'smart' watches, laptop computers, assets or equipment with an attached or incorporated Wi-Fi 'tag' or any other item with an attached or included Wi-Fi transmit or receive capability.

A Wi-Fi access point communicates with any devices which have associated with that access point using protocols defined in an agreed standard. The main standard presently in use for this purpose is the 802.11 standard and its various amendments, for example 802.11a, 802.11b, 802.1 lg, 802.11η and 802.1 lac, although any other suitable data communication standard could be employed, for example the HiperLAN standard. So long as both a Wi-Fi access point and a UE device both adhere to the same standard and suitable levels of the desired Wi-Fi signal and a sufficiently low level of interference exist in the immediate vicinity of both units, then communications between the Wi-Fi access point and the UE device should be possible. Various mechanisms have been proposed in order to spatially locate a person or object by means of locating a radio device which is present in the vicinity of the person or object, for example a radio unit attached to the object or located on the user's person. One mechanism which has been proposed is to utilise modulated light, emanating from, for example, a light-emitting diode (LED) based lightbulb as a means for the UE to spatially locate itself within an area upon which that light falls. The light emanating from the bulb is picked up by a camera or other light sensor on the UE (with such cameras being commonly fitted to 'smartphones', for example) and by interpreting the data modulated onto the light, emanating from one or more suitably- equipped bulbs, the UE is able to ascertain its spatial position. This mechanism has the obvious disadvantages that it will not work if the UE is unable to see the modulated light, such as if the UE is carried in a pocket or handbag, or if other sources of light, such as sunlight, are stronger, masking the modulated light. A further disadvantage from the viewpoint of the infrastructure provider is that whilst the UE is enabled to determine its spatial location the infrastructure itself gains no knowledge of the UE's location, unless the UE is willing or enabled to divulge that information. This is a particular problem in security-related applications since the UE could be programmed to 'lie' and report a different location to the place at which it was actually located.

Another spatial location mechanism often deployed is that of beacons. These beacons typically operate using the Bluetooth standard, since the required receiving and decoding equipment is commonly available (again being frequently included in 'smartphone' mobile telephony devices). A typical beacon will operate using the Bluetooth Low Energy (BLE) protocol standard and will periodically transmit a short burst of data, at a low EIRP (effective isotropic radiated power) level, which identifies the presence of the beacon to a UE containing a suitably-equipped receiver (such as a smartphone) and communicates a numerical code to the receiver which uniquely identifies that beacon from others located in the same area, for example in a store or shopping mall. Based upon a digital code number received from the beacon, software associated with the receiver can ascertain the beacon's location within an area, by means of a downloaded table of locations, and then ascertain broadly how close the receiver is located to the beacon, for example within lm of the beacon, by means of a signal strength measurement undertaken by the receiver upon the beacon's transmission. Based upon this information, a UE can spatially locate itself within an area and, if appropriate, communicate this calculated location to an external system, via an available radio bearer, such as Wi-Fi or cellular. Note that here, again, the UE locates itself and the infrastructure has no knowledge of the UE's location unless the UE willingly divulges this information (and does so truthfully).

A beacon-based spatial location system also suffers from a number of drawbacks. The management and maintenance of a sufficiently large number of beacons to enable accurate spatial location over a reasonable area, such as a shopping mall, is significant. Many hundreds of beacons are required and, in order to keep purchase and installation costs low, beacons are typically battery-powered. Each beacon therefore needs to be monitored regularly, to ensure that it is still operational and, in many cases, still present; beacons need to be placed very close (often <lm) to the people they are attempting to help to locate are therefore prone to theft. They are also frequently attached to their supporting surface, such as a wall, by some form of adhesive; when this fails, they fall off and are frequently lost. Wi-Fi has also been employed to spatially locate users or objects. In a typical scenario, the Wi-Fi transmissions emanating from a UE are received by three or more Wi-Fi access points, with these access points being spatially-separated from each other by suitable distances in order to permit triangulation of the UE to be undertaken. An example scenario is shown in Figure 1 ; in this figure, three Wi-Fi access points are shown, 101, 103 and 105, each with a corresponding locus of equal received signal strength, 102, 104 and 106, respectively. Each access point measures the strength of the signal received from the UE and conveys this information to a location-calculation algorithm. This algorithm assumes an appropriate propagation model for the signals emanating from an access point located in the relevant environment, such as a cluttered environment or an open, uncluttered environment. Based upon the chosen propagation model and the signal strength received from the UE, a radius is calculated at which the UE is likely to be located, generating a circular locus of possible points at which the UE could be located around the access point, for example locus 102 surrounding access point 101. This process is performed independently for the three access points 101, 103, 105, generating the corresponding loci 102, 104, 106. The algorithm then calculates the point at which these three loci intersect, 107, and this forms the calculated location of the UE.

Whilst this technique is sound, in theory, it has many practical drawbacks which severely limit the accuracy which may be obtained. For example, in a cluttered and dynamic environment, such as a shopping mall containing a number of customers who are actively mobile, the measured signal strength at each access point will vary dynamically as the environment changes, caused for example by the shoppers moving around. When this is combined with the fact that the theoretical variation of signal strength with distance, at other than very short distances from an access point, is very small for relatively large changes in distance, it is evident that small measurement errors in the signal strength, by one or more of the access points, can result in very large errors (10's of metres) in the spatial location reported by the algorithm.

A second Wi-Fi based spatial location technique involves the measurement of the difference in the signal propagation time from a UE to a number of antennas placed around the periphery of an access point. The access point implements an algorithm which searches, for example, for both the shortest propagation time and the longest propagation time for a given data burst to reach the antennas on the access point. It then assumes that the shortest propagation time corresponds to the antenna which is closest to the UE and the longest propagation time corresponds to the antenna which is furthest from the UE. The algorithm then traces a path from the antenna which registered the longest propagation time to the antenna which registered the shortest propagation time and this is interpreted to provide the bearing at which the UE sits relative to the access point. The propagation timing is then further interpreted to yield the distance at which the UE is located relative to the access point. The distance and bearing information is then combined with the known location of the access point to yield the spatial location of the UE.

Again, this approach has a number of disadvantages. Firstly, it is complex and large, typically requiring over 30 antennas to achieve a reasonable level of accuracy. Secondly, it is prone to misinterpreting information from reflected signals. Such signals will have a longer (often much longer) propagation time than will direct signals (which may be blocked by objects or people in a 'real world' environment). Any errors in this timing information can potentially severely impact both the bearing and distance calculations and thereby introduce significant errors into the reported spatial location.

Summary of invention

According to an aspect of the present invention there is provided an antenna array comprising a plurality of antenna elements grouped into at least a first sub-array and a second sub-array;

the first sub-array comprising a first sub-set of the plurality of antenna elements, the first sub-set comprising at least one bipolar antenna element, the first sub-array configured to act to radiate a first electromagnetic wave in a first polarisation; and

the second sub-array comprising a second sub-set of the plurality of antenna elements, the second sub-set comprising at least one bipolar antenna element, the second sub-array configured to act to radiate a second electromagnetic wave in a second polarisation

and wherein the first sub-array is not collinear with the second sub- array and the first sub-array and the second sub-array share a bipolar antenna element.

The plurality of antenna elements may be arranged in a rectilinear pattern.

The orientation of the primary axis of the first sub-array may subtend an angle of greater than 5 degrees and less than 175 degrees to the orientation of the primary axis of the second sub-array. According to a further aspect of the present invention, there is provided an antenna array consisting of a plurality of antenna elements arranged in a rectilinear pattern wherein antenna elements may be grouped into sub-arrays where each sub-array consists of a sub-set of the plurality of antenna elements and wherein a portion of the antenna elements are arranged to radiate an electromagnetic wave consisting of a single polarisation and others of the antenna elements are arranged to radiate an electromagnetic wave consisting of more than one polarisation, such that at least a pair of sub-arrays consist of at least one antenna element which is common to both sub- arrays comprising the pair of sub-arrays.

The antenna array may, for example, comprise at least a first sub-array and at least a second sub-array wherein the second sub-array is oriented substantially orthogonally to the first sub-array.

The antenna array may, for example, comprise at least one element which is common to both a first sub-array and a second sub-array, wherein the said at least one common element is arranged to radiate one or more signals as electromagnetic waves consisting of more than one polarisation.

The antenna array may, for example, comprise at least one element which is common to both a first sub-array and a second sub-array, wherein the said at least one common element is arranged to radiate one or more signals as electromagnetic waves consisting of two substantially orthogonal polarisations.

The feed arrangements or feed-point locations for antenna elements forming a first sub-array of the antenna array may be organised such that the a first sub-array radiates electromagnetic waves substantially in a first polarisation orientation and the feed arrangements or feed-point locations for antenna elements forming a second sub-array of the antenna array may be organised such that the a second sub-array radiates electromagnetic waves substantially in a second, substantially orthogonal, polarisation orientation, wherein the first sub-array and the second sub-array share at least a common antenna element.

The antenna and feed or feed-point arrangement discussed above may further incorporate a common antenna element which is arranged to radiate one or more signals as electromagnetic waves consisting of more than one polarisation The antenna array may, for example, comprise two or more sub-arrays arranged such that the centre point of each sub-array is located at a separation distance of at least one-half wavelength, defined at the centre frequency of the intended operating bandwidth of the array, from the centre point of any other sub-array.

The antenna array may, for example consist of at least two sub-arrays wherein a first sub-array is arranged substantially orthogonally to a second sub-array and wherein an end element of a first sub-array and an end element of a second sub-array is common to both sub-arrays.

Alternately or additionally, the antenna array may, for example consist of at least two sub-arrays wherein a first sub-array is arranged substantially orthogonally to a second sub-array and wherein an end element of a first sub-array and a mid-element of a second sub-array is common to both sub-arrays.

Alternately or additionally, the antenna array may, for example consist of at least two sub-arrays wherein a first sub-array is arranged substantially orthogonally to a second sub-array and wherein a mid-element of a first sub-array and a mid-element of a second sub-array is common to both sub-arrays.

Alternately or additionally, the antenna array may, for example consist of at least three sub-arrays wherein a first sub-array is arranged substantially orthogonally to a second sub-array and wherein an end element of a first sub-array and an end element of a second sub-array is common to both sub-arrays and wherein a third sub-array is arranged substantially orthogonally to the a second sub-array and wherein an end element of a second sub-array and an end element of a third sub-array is common to both sub-arrays.

Alternately or additionally, the antenna array may, for example consist of at least four sub-arrays wherein a first sub-array is arranged substantially orthogonally to a second sub-array and wherein an end element of a first sub-array and an end element of a second sub-array is common to both sub-arrays and wherein a third sub-array is arranged substantially orthogonally to the a second sub-array and wherein an end element of a second sub-array and an end element of a third sub-array is common to both sub-arrays and further wherein a fourth sub-array is arranged substantially orthogonally to the a third sub-array and wherein an end element of a fourth sub-array and an end element of a third sub-array is common to both sub-arrays.

The antenna array described above may be configured with a square or rectangular distribution of antenna elements comprising the four sub-arrays.

The antenna array may comprise antenna elements arranged to at least one of radiate linear polarisations or receive linear polarisations wherein, for example, a vertical linear polarisation is orthogonal to a horizontal linear polarisation.

The antenna array may comprise antenna elements arranged to at least one of radiate circular polarisations or receive circular polarisations wherein, for example, a right- hand circular polarisation is orthogonal to a left-hand circular polarisation.

According to a further aspect of the present invention, there is provided an antenna array consisting of a plurality of antenna elements arranged in a rectilinear pattern wherein

antenna elements may be grouped into sub-arrays where each sub-array consists of a sub-set of the plurality of antenna elements; and

a portion of the antenna elements are arranged to radiate an electromagnetic wave consisting of a single polarisation and others of the antenna elements are arranged to radiate an electromagnetic wave consisting of more than one polarisation, such that at least one sub-array is able to share one or more antenna elements with at least a second sub-array and at least two sub-arrays are operably coupled to at least one channel each of a multiple-input, multiple output (MIMO) transceiver.

According to a further aspect of the present invention, there is provided a spatial location system comprising at least one of a transmitter and a receiver together with an antenna array of a form disclosed herein wherein the antenna array is capable of varying a pointing angle of at least two antenna lobes independently under electronic control without the need to move either the antenna array or its constituent parts physically and wherein the at least two antenna lobes are arranged such that they may intersect at one or more pointing angles.

The at least a first sub-array may be arranged to generate at least a first lobe and the at least a second sub-array may be arranged to generate at least a second lobe wherein at least one of the first lobe and the second lobe has a shape which is substantially elongated in one plane and substantially narrower in a second, orthogonal, plane.

The at least a first lobe generated by the at least a first sub-array and the at least a second lobe generated by the at least a second sub-array may be arranged such that the direction in which the at least a first lobe is elongated is oriented substantially orthogonally to the direction in which the at least a second lobe is elongated.

The pointing angle of an antenna lobe of a first sub-array and the pointing angle of an antenna lobe of a second sub-array may be independently controllable in order to allow each to separately measure or locate a signal which falls within their respective steering ranges or to transmit a signal or signals for measurement by a remotely- located receiver.

According to a further aspect of the present invention, there is provided a method by which a first antenna lobe and a second antenna lobe may be steered independently in order to locate a remote transmitting or receiving station which falls within their respective steering ranges, the method comprising:

Steering, electronically, a first antenna lobe to maximise a signal received from or by a remote station at a given point in time;

Steering, electronically, a second antenna lobe to maximise the reported strength of a signal received from or by the same or a substantially co-located remote transmitting or receiving station at substantially the same point in time, wherein the reported signal associated with the first antenna and the reported signal associated with the second antenna may result from the same signal;

Determining a region of intersection of the first steered antenna lobe and the second steered antenna lobe; and Reporting, to a further process or system, a point within the area of intersection as a location of the received signal.

The above method may further comprise a method by which a third antenna lobe may be steered independently of, or in conjunction with, any other steered antenna lobes in order to further or additionally locate a remote transmitting or receiving station which falls within its steering range, the method further comprising:

Steering, electronically, a third antenna lobe to maximise the strength of a signal received from or by a remote transmitting or receiving station at a given point in time;

Determining an area of intersection of any two or more steered antenna lobes; and

Reporting, to a further process or system, a point within the area of intersection as a location of the received signal.

The above method may additionally comprise a method by which a fourth antenna lobe may be steered independently of, or in conjunction with, any other steered antenna lobes in order to further or additionally locate a signal received from or by a remote transmitting or receiving station which falls within its steering range, the method further comprising:

Steering, electronically, a fourth antenna lobe to maximise the strength of a signal received from or by a remote transmitting or receiving station at a given point in time;

Determining an area of intersection of any two or more steered antenna lobes; and

Reporting, to a further process or system, a point within the area of intersection as a location of the received signal.

In any of the above methods, the steering of an antenna lobe to maximise the strength of a signal received from or by a remote source could instead be implemented as the steering of an antenna radiation pattern to minimise the strength of a signal received from or by a remote transmitting or receiving station, thereby steering the radiation pattern to locate the signal received from or by the remote source within a null in the antenna radiation pattern.

Likewise, in any of the above methods, the steering of an antenna lobe to maximise the strength of a signal received from a remote transmitting or receiving station could instead be implemented as the correlation of all or a part of a known antenna radiation characteristic, measured at a known angular position relative to a known datum, such as the boresight direction of the antenna array, in order to determine the angular location of a remote transmitting or receiving station.

Brief description of the drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which:

Figure 1 is an outline view of a network architecture showing overlapping lines of constant received signal strength; Figure 2 is a block diagram of an access point incorporating a beamforming system according to the present invention;

Figure 3(a) is a schematic planar view of an antenna array; Figure 3(b) is a schematic planar view of an alternative antenna array;

Figure 3(c) is a schematic planar view of a further alternative antenna array; Figure 3(d) is a schematic planar view of a still further alternative antenna array;

Figure 4(a) shows a wireframe representation of a top view of an idealised approximation of an antenna radiation pattern of the form which could emanate from a horizontally-oriented linear multi-element antenna array; Figure 4(b) shows a wireframe representation of a side view of an idealised approximation of an antenna radiation pattern of the form which could emanate from a linear multi-element antenna array;

Figure 4(c) shows a wireframe representation of a front (boresight) view of an idealised approximation of an antenna radiation pattern of the form which could emanate from a linear multi-element antenna array; Figure 4(d) shows a wireframe representational 3D view of an approximation of an idealised antenna radiation pattern of the form which could emanate from a linear multi-element antenna array;

Figure 5(a) shows a wireframe representation of a rear (boresight) view of an approximation of two intersecting antenna radiation patterns of the form which could emanate from a horizontally-oriented linear multi-element antenna array and a vertically-oriented linear multi-element antenna array;

Figure 5(b) shows a detail view of intersecting wireframe radiation patterns of a form shown in Figure 5(a), highlighting a rectilinear area of intersection;

Figure 5(c) illustrates the orientations of azimuth and elevation in relation to the diagrams shown in Figure 5(a) and Figure 5(b); Figure 6(a) shows a wireframe representation of a top view of a simplified, but representative, approximation of an antenna radiation pattern of the form which could emanate from a horizontally-oriented linear multi-element antenna array. The representation shown includes side-lobes and nulls in the radiation pattern; Figure 6(b) shows a three-dimensional wireframe representation of a simplified, but representative, approximation of an antenna radiation pattern of the form which could emanate from a linear multi-element antenna array. The representation shown includes side-lobes and nulls in the radiation pattern; Figure 7(a) is similar to figure 5(a) and shows a wireframe representation of a rear (boresight) view of an approximation of two intersecting antenna radiation patterns of a form which could emanate from a horizontally-oriented linear multi-element antenna array and a vertically-oriented linear multi-element antenna array. In figure 7(a), however, two loci of points representing peak gains of the two antenna array radiation patterns, at various offset angles from boresight in one plane, are clearly shown;

Figure 7(b) shows a similar example situation to that of Figure 7(a) however in this example a radiation pattern from an azimuth-oriented antenna array (not shown) is illustrated when pointing in a lower elevation altitude direction; this view therefore illustrates a different intersection location between the two loci shown;

Figure 8 shows simplified 2D orthogonal radiation patterns emanating from two orthogonal antenna arrays (or sub-arrays) placed on a ceiling of a room and radiating directly downward toward the floor of the room;

Figure 9 shows example simplified orthogonal radiation patterns emanating from two orthogonal antenna arrays (or sub-arrays) oriented to provide a downward-pointing angle between a wall and a ceiling of a room and radiating at an angle toward the floor of the room;

Figure 10 shows a locus of the intersection between the two example simplified orthogonal radiation patterns shown in Figure 9 and a projection of the intersection of the example simplified orthogonal radiation patterns themselves with the floor of the room;

Figure 11(a) shows a similar situation to that of figure 6(a) with the exception that the beam has been steered approximately 15 degrees to the left of boresight. This figure illustrates a signal strength level reading which could be expected from a user located approximately on the original boresight position of the antenna array; Figure 11(b) shows a similar situation to that of figure 11(a) with the exception that the beam has now been steered approximately 10 degrees to the right of boresight. This figure illustrates a further signal strength level reading, obtained in this new steered direction, which could be expected from a user located approximately on the original boresight position of the antenna array. It also illustrates the difference between the signal strength values which could be obtained in the two steered positions illustrated in Figures 11(a) and 11(b);

Figure 12 shows a flow-chart representation of an example method for determining an angle at which a UE is located relative to a known datum angle, for example a boresight angle of an antenna array.

Figure 13 shows four different views of an example antenna array beam pattern as it is swept or scanned from left to right, covering a range of angles relative to the plane of an antenna array;

Figure 13(a) shows a first example beam location for a swept or scanned antenna beam; Figure 13(b) shows a second example beam location for a swept or scanned antenna beam;

Figure 13(c) shows a third example beam location for a swept or scanned antenna beam;

Figure 13(d) shows a fourth example beam location for a swept or scanned antenna beam.

Figure 14 shows a flow chart representation of one embodiment of a method of locating a UE.

Figure 15 shows a flow chart representation of a further embodiment of a method of locating a UE. Figure 16(a) shows an example of a reference antenna beam pattern.

Figure 16(b) shows an example of an antenna beam pattern of a type which could result from measurements taken using an in-situ (installed) receiver or transceiver system incorporating a steerable antenna system, in a representative physical environment.

Figure 16(c) shows an example result achieved when performing one form of correlation processing using the example antenna beam patterns shown in Figure 16(a) and Figure 16(b).

Figure 17 shows a flow chart representation of a still further embodiment of a method of locating a UE.

Figure 18(a) shows an example of a reference antenna beam pattern.

Figure 18(b) shows a coarsely quantised example of an antenna beam pattern of a type which could result from measurements taken using an in-situ (installed) receiver or transceiver system incorporating a steerable antenna system, in a representative physical environment.

Figure 18(c) shows an example result achieved when performing one form of correlation processing using the example antenna beam patterns shown in Figure 18(a) and Figure 18(b).

Figure 19 shows an example configuration for an antenna array incorporating the sharing of some elements between sub-arrays within the antenna array.

Figure 20 shows a further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array. Figure 21 shows a yet further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array. Figure 22 shows a still further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array.

Figure 23 shows a still further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array.

Figure 24 shows a still further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array.

Figure 25 shows a still further example configuration for an antenna array incorporating the sharing of one or more elements between sub-arrays within the antenna array.

Figure 26 shows an example of one embodiment of an antenna element capable of dual-polar operation.

Figure 27 shows an example of a further embodiment of an antenna element capable of dual-polar operation.

Figure 28 shows an example of a yet further embodiment of an antenna element capable of dual-polar operation. Detailed description

An antenna system, suitable for use within a Wi-Fi access point which is capable of accurate geolocation and an extended coverage range, will now be described with reference to the accompanying drawings. The antenna system and access point to be described are capable of accurate geolocation without requiring any additional information from other, neighbouring, access points, for example signal strength measurement information of the signal strength received from a UE at a location within the coverage area of a second access point and measured by that second access point. Furthermore, the antenna system and access point to be described are capable of accurate geolocation without requiring a distance or range calculation of the range or distance of a UE from the access point using, for example, signal strength information or signal propagation time information. Eliminating the need to calculate the distance at which a UE is located relative to the position of an access point is a significant benefit of the antenna system and access point to be described herein, since it eliminates the main sources of error in utilising prior art access points for geolocation purposes.

An example of the form of an access point 200 which is capable of accurate geolocation and an extended coverage range is shown in Figure 2. The access point connects to a data network, for example an Internet Protocol (IP) network, via an interconnection 210, which could, for example, take the form of a CAT5, CAT5e or CAT6 cable or a fibre-optic cable or any other suitable connection means.

Network data signals are transmitted over a data network and received from a data network by means of network interface 201. Network interface 201 translates the data signals to and from a network protocol, such as the Internet Protocol, and feeds user data and other data to a processor/control system 202. This processor/control system fulfils at least two primary functions: firstly it performs further processing upon user and other data received from network interface 201 and passes this further processed data to transceiver circuits 203 as well as, separately, processing the data received from transceiver circuits 203 and performing processing on this data before feeding it to network interface 201; secondly it generates control signals which are fed to beam- forming subsystems 204, 205 and 206. In many access point implementations, processor/control system 202 and transceiver circuits 203 are implemented as integrated circuits and in some of these implementations processor/control system 202 and transceiver circuits 203 are integrated into the same integrated circuit.

The example of an access point system provided in Figure 2 shows three beamforming subsystems 204, 205 and 206, however this should not be taken as a limiting example and a greater or a lesser number of beamforming subsystems may be controlled by processor/control system 202. Specifically, in an example configuration in which transceiver circuits 203 consist of 4x4 multiple-input, multiple-output (MIMO) transceiver circuits, then up to four beam-forming subsystems could be connected to processor/control system 202. Likewise, in a further example configuration in which transceiver circuits 203 consist of 2x2 multiple-input, multiple-output (MIMO) transceiver circuits, then as few as two beam-forming subsystems may be connected to processor/control system 202.

Beamforming subsystems 204, 205 and 206 are connected to antenna elements forming antenna arrays (or sub-arrays) 207, 208 and 209 respectively. For example, beam-forming subsystem 204 connects to antenna elements 207a, 207b, 207c and 207d in antenna array 207. Likewise, beam-forming subsystem 205 connects to antenna elements 208a, 208b, 208c and 208d in antenna array 208 and beam-forming subsystem 206 connects to antenna elements 209a, 209b, 209c and 209d in antenna array 209. The operation of beamforming subsystems 204, 205 and 206, together with antenna arrays (or sub-arrays) 207, 208 and 209 and transceiver circuits 203 will be described in more detail below.

In one embodiment, transceiver circuits 203 could consist of digital transmitter and receiver circuits which act to form digital representations of modulated signals to be transmitted, in their transmit circuitry, or to decode or demodulate digital representations of modulated received signals, in their receive circuitry. In this embodiment, signals transmitted to and received from beam-formers 204, 205 and 206 could be digital signals and the beam-formers 204, 205 and 206 could be digital beam- formers, in which amplitude and/or phase weightings are imposed upon the signals they process digitally (separately or together in either transmit or receive directions), for example by means of digital multiplication of these amplitude and phase weightings with digital representations of the signals passing through the beam- formers, in order to present signals which, when converted to or from analogue form, serve to point the beams formed by antenna arrays (or sub-arrays) 207, 208 and 209 in one or more desired directions. In another embodiment, transceiver circuits 203 could consist of both digital and analogue transmitter and receiver circuits which act to form analogue modulated signals to be transmitted, in their transmit circuitry, or to decode or demodulate analogue modulated received signals, in their receive circuitry. In this embodiment, signals transmitted to and received from beamformers 204, 205 and 206 could be analogue signals and the beamformers 204, 205 and 206 could be analogue beam- formers, in which amplitude and/or phase weightings are imposed upon the signals they process using passive or active analogue signal processing techniques (separately or together in either transmit or receive directions), for example by means of a Rotman Lens, a Butler Matrix, a Blass Matrix or a Nolen Matrix or any other suitable circuit configuration as is known in the art, in order to present signals which serve to point the beams formed by antenna arrays 207, 208 and 209 in one or more desired directions.

In one embodiment, processor/control system 202 may provide beam position information, coefficients or co-ordinates, in the form of gain, amplitude or phase weightings, in-phase and quadrature weightings, or any other suitable mechanism and in a suitable format such that beam-formers 204, 205 and 206 can direct one or more beams emanating from antenna arrays (or sub-arrays) 207, 208 and/or 209 in directions determined by the processor/control system 202. In this way, processor/control system 202 is able to control the direction of beams formed by beam-formers 204, 205 and 206 in either or both of transmit and receive directions and is further capable of steering beams in different directions for transmit and receive signals from the same antenna array by means of applying different beam-forming coefficients to received signals than those applied to transmit signals. This may be possible, without recourse to duplex or diplex filtering of transmit and receive signals, since many systems, for example Wi-Fi systems, such as those based upon the IEEE 802.11 standards, utilise a time-division duplex (TDD) protocol with transmission and reception times being divided into separate time-slots or frames and it is therefore possible to select different beam-steering coefficients during receive time-slots to those used during transmit time-slots. Furthermore, it is possible to steer individual transmit and receive beams to individual UEs, since each time-slot, from a given access point, is typically dedicated to transmitting signals to or receiving signals from a single UE.

Take, as an example, an access point AP#1 which has two UEs: UE#1 and UE#2, associated with it. Both UEs are assumed to be actively transmitting and receiving data from the access point quasi-simultaneously. UE#1 transmits its first data packet to access point AP#1 in time-slot #1 and beamformers 204, 205 and 206 accept beam- steering coefficients 204-UE#l-Rx, 205-UE#l-Rx and 206-UE#l-Rx respectively. It is not necessary that the beams formed by the three arrays 207, 208 and 209 point in the same or a similar direction as each other; it may be, for example, that one or more beams are directed to receive one or more strong reflected signals from UE#1 rather than a direct signal.

In time-slot #2, UE#2 is expecting to receive its first data packet from access point AP#1 and beamformers 204, 205 and 206 in access point AP#1 accept beam-steering coefficients 204-UE#2-Tx, 205-UE#2-Tx and 206-UE#2-Tx respectively, which act to direct transmit beams from access point AP#1 to best serve UE#2 with its intended data packet. Again, beams formed by the three arrays 207, 208 and 209 may not point in the same direction as each other.

In time-slot #3, UE#1 is expecting to receive its first data packet from access point AP#1 and beamformer 204, 205 and 206 in access point AP#1 accept beam-steering coefficients 204-UE#l-Tx, 205-UE#l-Tx and 206-UE#l-Tx respectively, which act to direct transmit beams from access point AP#1 to best serve UE#1 with its intended data packet. Again, beams formed by the three arrays 207, 208 and 209 may not point in the same direction as each other.

In time-slot #4, UE#2 is expecting to transmit its first data packet from access point AP#1 and the beam-formers 204, 205 and 206 in access point AP#1 accept beam- steering coefficients 204-UE#2-Rx, 205-UE#2-Rx and 206-UE#2-Rx respectively, which act to direct transmit beams from access point AP#1 to best receive a data packet from UE#2. Again, beams formed by the three arrays 207, 208 and 209 may not point in the same direction as each other.

This process of beam-steering to best serve UEs in respect of their transmitted and received data packets can continue in a similar manner, utilising different or the same beam-steering coefficients for each UE and different or the same beam-steering coefficients for transmit (downlink) or receive (uplink) signals. Note that the order of transmit and receive data packets outlined above is not proscriptive. For example, it may be that two or more downlink data packets occur directed at a single UE or separately at more than one UE and that these packets are consecutive, with no intervening uplink data packet. Likewise, it may be that two or more uplink data packets occur directed at a single UE or separately at more than one UE and that these packets are consecutive, with no intervening downlink data packet. Beamforming coefficients may be assigned to each packet in the manner outlined above, with different or the same coefficients being used in the uplink or downlink directions and different or the same coefficients being used for one or more UEs.

The above discussion has been simplified for clarity and does not include discussion of any broadcast packets, such as beacon packets, any acknowledgement packets and the like.

A further aspect of the beam-steering system described above is that individual beams formed by each separate antenna array 207, 208, 209 may be formed simultaneously when considering a MIMO transmitter and receiver system, which is typical of most higher-performance Wi-Fi access points. So, for example, antenna array 207 may be connected to MIMO transmit/receive channel Ml, antenna array 208 may be connected to MIMO transmit/receive channel M2 and antenna array 209 may be connected to MIMO transmit/receive channel M3. Channels Ml, M2 and M3 will typically act in unison, from a transmit/receive perspective, for example, if a block of data is being sent to UE#1, then channel Ml will be used to transmit some or all of that block of data, likewise, channel M2 will also be used to transmit some or all of that block of data simultaneously with the corresponding transmission of some or all of the same block of data from channel Ml and channel M3 will further be used to transmit some or all of the same block of data simultaneously with the corresponding transmissions of some or all of the same block of data from channels Ml and M2. Thus, three antenna beams can be formed simultaneously, one for each of channel Ml, channel M2 and channel M3, in a given transmit or receive time-slot, all serving the same UE. It is this simultaneous forming of independently-steerable beams, from a single access point, transmitting one or more data packets to a single UE, which is a key enabling aspect of the high-accuracy geolocation system to be described below.

The above discussion has highlighted one example method by which multiple, individual, beams may be directed toward a single UE. It has illustrated the principle based upon a 3x3 MIMO access point example, as three MIMO channels and three beams were discussed. It is evident that three MIMO channels is not a limiting case and that beam-steering of a single channel, two channels (2x2 MIMO) and four or more channels (4x4 MIMO and above) are also possible.

Likewise the example of using Wi-Fi as the bearer to transmit and receive data from a UE is not a limiting case and other time-division duplex, frequency-division duplex and code-division duplex air interfaces or bearers may be used, together with appropriately-designed beam-formers and antenna arrays (or sub-arrays), involving duplex filtering when appropriate.

In order to utilise the above-discussed or similar beam-forming techniques for spatial location or geolocation purposes, the configuration and orientation of the beam- forming antenna arrays (or sub-arrays) 207, 208 and 209 is important. This aspect of the system will now be discussed with reference to Figure 3.

Combined antenna array 300, shown in Figure 3(a), consists of three main arrays corresponding to an example intended application in a 3x3 MIMO system and an optional fourth array which could be employed where a 4x4 MIMO system is required. The three main arrays are formed as follows: array #1 consists of antenna elements 301a, 301b, 301c and 30 Id; array #2 consists of antenna elements 302a, 302b, 302c and 302d; array #3 consists of antenna elements 303a, 303b, 303c and 303d and optional array #4 consists of antenna elements 304a, 304b, 304c and 304d. Array #1, array #2, array #3 and array #4 may also be considered as sub-arrays of combined antenna array 300. In Figure 3(a), the antenna arrays (or sub-arrays) are configured in an approximately square arrangement, with four antenna elements corresponding to a single antenna array and each antenna array is arranged to be oriented in a perpendicular direction to its neighbouring arrays, to form combined antenna array 300. It should be appreciated that although antenna arrays (or sub-arrays) of four elements each are shown in Figure 3(a), with a total combined antenna array size of 16 elements being shown in that figure, arrays of other sizes, numbers of elements and configurations are possible, some of which will be outlined below. Individual antenna arrays (or sub-arrays) consisting of larger numbers of elements will typically result in a narrower main lobe beam being formed by each individual antenna array, when fed with suitably-phased signals as provided by one of the beam-formers 207, 208, 209 of Figure 2 and assuming that the spacing between the individual antenna elements is similar in both cases. Likewise, individual antenna arrays (or sub-arrays) consisting of smaller numbers of elements will typically result in a broader main lobe beam being formed by each individual antenna array, when fed with suitably-phased signals as provided by one of the beam-formers 207, 208, 209 of Figure 2 and assuming that the spacing between the individual antenna elements is again similar in both cases. Other, typical, individual antenna array sizes could be, for example, two elements (giving a combined antenna array 300 size of, for example, 8 elements for a 4x4 MIMO system), eight elements (giving a combined antenna array 300 size of, for example, 32 elements for a 4x4 MIMO system) and sixteen elements (giving a combined antenna array 300 size of, for example, 64 elements for a 4x4 MIMO system) although other options are also possible.

The individual antenna elements, for example antenna elements 301a to 301 d, 302a to 302d, 303a to 303d, 304a to 304d, shown in Figure 3(a) can be implemented in a wide variety of ways, including as: microstrip patch elements, air-spaced patch elements, dielectric-spaced (e.g. insulating foam spaced) patch elements, monopole antennas, dipole antennas, helical antennas, dielectric resonator antennas, 'chip' dielectric antennas, inverted-F type antennas, Yagi antennas with any number of directors and/or reflectors and whether formed from wire, etched copper on a dielectric substrate or rigid metal structures, horn antennas, reflector/dish-based antennas, wire antennas or any other form of antenna element whether linearly, circularly, slant or otherwise polarised. The main stipulations for these antenna elements are that, within a given antenna array, they should be capable of emanating or receiving signals which combine coherently to form a recognised beam shape and which permit the beam to be manipulated by means of altering the amplitude and/or phase of one or more of the signals feeding, or being sourced from, one or more of the antenna elements. In this instance, 'manipulated' is defined as some or all of altering the shape, make-up including the number of lobes, side-lobes, nulls and other beam characteristics, and pointing direction of a main lobe, a side-lobe or a null of at least one of the transmit and receive beam characteristics. Returning now to combined antenna array 300, shown in Figure 3(a), and which can be seen to consist of three main antenna arrays or sub-arrays (excluding elements 304a, 304b, 304c and 304d shown using dashed lines in Figure 3(a)) as discussed above for example when considering an intended application in a 3x3 MIMO system. It can be seen that array #1, consisting of antenna elements 301a, 301b, 301c and 301 d, and array #2 consisting of antenna elements 302a, 302b, 302c and 302d, are arranged orthogonally to one another. Likewise array #1, consisting of antenna elements 301a, 301b, 301c and 30 Id, and array #3 consisting of antenna elements 303a, 303b, 303c and 303d, are arranged orthogonally to one another. This configuration, shown in Figure 3(a), may typically yield beams and beam patterns which are orthogonal to one another, specifically a beam pattern emanating from array #1 will typically be orthogonal to a corresponding beam pattern emanating from array #2; likewise, a beam pattern emanating from array #1 will typically be orthogonal to a corresponding beam pattern emanating from array #3. Such orthogonality is not limited to orthogonality of polarisation, which may or may not result of an orthogonality of array orientation, depending upon how the individual antenna elements for example 301a, 301b, 301c and 301 d and 302a, 302b, 302c and 302d are driven from a polarisation perspective, it will also encompass or exclusively encompass the shape of the respective beams or beam patterns. For example, if array #1, consisting of antenna elements 301a, 301b, 301c and 30 Id were to form a main lobe which was substantially broader in the elevation plane than it was in the azimuth plane, then array #2, consisting of antenna elements 302a, 302b, 302c and 302d and which is of similar construction to array #1 but with a vertical arrangement of elements rather than the horizontal arrangement shown in the case of array #1, could form a main lobe which was substantially broader in the azimuth plane than it was in the elevation plane. Likewise, in this example, array #3 which consists of antenna elements 302a, 302b, 302c and 302d and which is again of similar construction to array #1 but with a vertical arrangement of elements rather than the horizontal arrangement shown in the case of array #1, could form a main lobe which was again substantially broader in the azimuth plane than it was in the elevation plane.

It should be remembered that these three beams, with their respective main lobe shapes, emanating from array #1, array #2 and array #3 respectively, are typically formed, simultaneously, from independent transmission streams, one for each of the three MIMO channels in this example, and are not typically formed from three identical copies of the same transmission stream, although this example should not be taken as limiting to the invention described herein. These three transmission streams can therefore be analysed independently by the UE, if it has such capabilities. For example, signal strength values can be measured for each of the three streams independently. Likewise, transmissions from the UE, even single-stream transmissions in the case where a UE is not configured to generate 3x3 or 2x2 MIMO signals, will be received independently by the three MIMO antenna arrays (or sub- arrays) making up combined array 300. Each of the three main antenna arrays (or sub-arrays), 301a - 301d, 302a - 302d, 303a - 303d, making up combined array 300 can measure the strength of a signal emanating from the (or each) UE and thereby judge from what angle to boresight, a main lobe, a side-lobe or a null the UE's transmission is emanating, as will be outlined below. The ability to make two or more (three in the above example) independent signal strength measurements, from two or more (three in the above example) independent antenna arrays (or sub-arrays) any of at least two of which are at least one of being orthogonal to each other and capable of generating orthogonal beam pattern shapes, is a unique benefit of the access point disclosed here and one aspect of forming a spatial location capability using a single access point. Figure 3(b) shows an alternative form 310 of an antenna array according to a further aspect of the present invention. The arrangement shown in Figure 3(b) can illustrate at least three different options: a 2x2 MIMO configuration with orthogonal beam pattern shapes; a 3x3 MIMO configuration with at least two orthogonal beam pattern shapes and a 4x4 MIMO configuration with at least two orthogonal beam pattern shapes, as will now be described.

Taking the 2x2 MIMO case, antenna elements 311a, 311b, 311c and 3 l id form antenna array #11 and antenna elements 312a, 312b, 312c and 312d form antenna array #12; antenna array #11 and antenna array #12 are similar arrays, with antenna array #11 being mounted orthogonally to antenna array #12. Both antenna array #11 and antenna array #12 are typically, although not necessarily, single polarisation arrays consisting of single-polar antenna elements, 311a, 311b, 311c, 31 Id and 312a, 312b, 312c, 312d respectively. Combined array 310 is therefore capable of fulfilling, in conjunction with one or more beam-formers and other elements of an access point, the desired aims of, at least, generating independently-steerable, orthogonal, beam- pattern shapes an elevation beam-pattern of which is significantly different to that of a corresponding azimuth beam-pattern, simultaneously from at least two independent transmission or reception streams, such as MIMO channels.

Taking now the 3x3 MIMO case, antenna elements 311a, 311b, 311c and 31 Id for example now form two antenna arrays (or sub-arrays) which are now required to radiate two polarisations simultaneously, antenna array #11 A and antenna array #1 IB, with antenna array #11 A having, say, vertical polarisation and antenna array #11B having horizontal polarisation and antenna elements 312a, 312b, 312c and 312d, forming antenna array #12, a single-polarisation array, as before. Antenna array #11 A and antenna array #11B would typically share the same radiating elements as shown in Figure 3(b), although this need not always be the case for example if crossed-dipole or crossed Yagi antenna elements are used; the two co-located antenna arrays (or sub-arrays) would typically be distinguished by utilising separate feed- systems, to achieve two orthogonal polarisations for the electromagnetic waves emanating from the radiating element(s), with suitable antenna element and feed- system designs including, but not limited to: dual-probe fed patch antennas, dual- aperture fed patch antennas, crossed-dipole antennas, crossed- Yagi antennas, left and right-hand circular polarisation radiating structures and any other suitable structures capable of generating two substantially orthogonal polarisations. Antenna array #11, consisting of antenna array #11 A and antenna array #11B, and antenna array #12 are ostensibly similar arrays to one another, excepting the features discussed above, a key difference being, however, that antenna array #11 is oriented orthogonally to antenna array #12. Antenna array 310 is therefore capable of fulfilling, in conjunction with one or more beam-formers and other elements of an access point, the desired aims of, at least, generating independently-steerable, orthogonal, beam-pattern shapes the elevation beam-pattern of which is significantly different to that of the corresponding azimuth beam-pattern, simultaneously from at least two (and in this case, three) independent transmission or reception streams, such as MIMO channels.

A further embodiment, similar in operation to that just described, consists of a single- polarisation array, antenna array #11, formed from antenna elements 311a, 311b, 311c, 31 Id and a dual-polarisation array, consisting of antenna array #12a and antenna array #12b and comprising antenna elements 312a, 312b, 312c, 312d which are now required to radiate two polarisations simultaneously. In effect, this embodiment simply swaps the dual-polarisation aspects of the earlier embodiment from antenna elements 311a, 311b, 311c and 31 Id to antenna elements 312a, 312b, 312c and 312d. In other respects operation is similar to that just described.

A yet further embodiment, which can also be illustrated by Figure 3(b), involves the use of two dual-polarisation antenna arrays (or sub-arrays), with each array/polarisation being fed by a separate MIMO channel in say a 4x4 MIMO system implementation. Dual-polar antenna array #11 consists of, for example, vertical polarisation antenna array #11 A and horizontal polarisation antenna array #1 IB, both of which are formed using antenna elements 311a, 311b, 311c and 3 l id which are capable of radiating electromagnetic waves in both polarisations simultaneously. Dual-polar antenna array #12 consists of, for example, vertical polarisation antenna array #12A and horizontal polarisation antenna array #12B, both of which are formed using antenna elements 312a, 312b, 312c and 312d which are also capable of radiating electromagnetic waves in both polarisations simultaneously. The operation of this combined antenna array is similar to that discussed above in relation to the 3x3 MIMO example, however now with an extra MIMO channel and an extra polarisation with which to accommodate that channel. Any two polarised beams with typically one each from a vertically-oriented array consisting of antenna elements 312a, 312b, 312c, 312d and a horizontally-oriented array consisting of antenna elements 311a, 311b, 311c, 31 Id, are capable of fulfilling, in conjunction with one or more beamformers and other elements of an access point, the desired aims of, at least, generating independently-steerable, orthogonal, beam-pattern shapes an elevation beam-pattern of which is significantly different to that of a corresponding azimuth beam-pattern, simultaneously from at least two (and in this case, three) independent transmission or reception streams, such as MIMO channels.

Whilst the embodiments described above discuss the formation of orthogonal linear polarisations utilising two feed systems in antenna array #11 or antenna array #12 or both, it is also possible to utilise orthogonal circular polarisations, such as left-hand and right-hand circular polarisation, to achieve the same goal.

The above embodiments discuss specific 'vertical' and 'horizontal' orientations for the various antenna arrays (or sub-arrays), however such vertical and horizontal arrays could be interchanged with typically no loss of functionality. Likewise the combined arrays 300, 310, 320, 330 shown in Figure 3(a) - (d) can be rotated to any arbitrary angle without impacting operation in most cases; specifically a rotation of any of the combined arrays 300, 310, 320, 330 by a multiple of 90 degrees could be undertaken without loss of functionality in many applications. Furthermore, it is possible to rotate the individual antenna arrays (or sub-arrays), for example antenna array #1 discussed in relation to Figure 3(a) or antenna array #12 discussed in relation to Figure 3(b) or any other array discussed in relation to any of Figure 3(a)— (d), by an arbitrary angle with potentially only a minor loss of functionality. The ideal angle between any two notionally orthogonal arrays shown in any of Figure 3(a) - (d) is 90 degrees and the larger the deviation from this figure, either increasing or decreasing, typically the poorer will be the geolocation performance until a deviation of +/-90 degrees has been reached (i.e. the angle between two arrays reaches zero degrees or 180 degrees) when a very poor level of spatial location or geolocation accuracy of a UE is likely to result. Any array which is capable of producing a measurable beam intersection between two beams generated by two physically-separated antenna arrays (or sub-arrays), served by different MIMO channels from the same access point will fulfil the basic requirements necessary for the operation of the spatial location or geolocation system which will be described in more detail below.

Figure 3(c) shows a combined antenna array 320 which consists of three separate antenna arrays (or sub-arrays), with the first formed from antenna elements 321a, 321b, 321c, 321d, the second formed from antenna elements 322a, 322b, 322c, 322d and the third formed from antenna elements 323a, 323b, 323c, 323d. In a similar manner to that discussed in relation to Figure 3(b), an antenna array formed from antenna elements 322a, 322b, 322c, 322d may be a dual-polarisation array similar to that of an array formed from antenna elements 312a, 312b, 312c, 312d shown in Figure 3(b). Likewise an antenna array formed from antenna elements 321a, 321b, 321c, 321d may be a single-polarisation array similar to that of an array formed from antenna elements 301a, 301b, 301c, 301d shown in Figure 3(a) and an antenna array formed from antenna elements 323a, 323b, 323c, 323 d may be a single-polarisation array similar to that of an array formed from antenna elements 301a, 301b, 301c, 301d shown in Figure 3(a). The operation of these arrays and the beam-patterns formed are similar to the corresponding array operation and beam patterns discussed in relation to the corresponding diagrams discussed above. Furthermore, whilst the above discussion was based around dual-polar operation of an antenna array formed from antenna elements 322a, 322b, 322c, 322d, it is equally possible that an antenna array formed from antenna elements 321a, 321b, 321c, 321d could be dual-polarisation, with the remaining two arrays shown in Figure 3(c) being single polarisation and likewise, it is also possible that an antenna array formed from antenna elements 323a, 323b, 323c, 323d could be dual-polarisation, with the remaining two arrays shown in Figure 3(c) being single polarisation Figure 3(d) is, in essence, a modified version of Figure 3(b), with antenna elements 331a, 331b, 331c and 331d corresponding to antenna elements 311a, 311b, 311c and 31 Id respectively and antenna elements 332a, 332b, 332c and 332d corresponding to antenna elements 312a, 312b, 312c and 312d respectively. It could simply be viewed as a version of Figure 3(b) in which antenna elements 312a, 312b, 312c and 312d have been moved to the right, such that they now form a rotated 'L' or corner shape in conjunction with antenna elements 311a, 311b, 311c and 31 Id (which have been renumbered as 331a, 331b, 331c and 33 Id in Figure 3(d)). The operation of the configuration shown in Figure 3(d) is therefore similar to that of Figure 3(b) in relation to all of the MIMO variants discussed above in relation to that figure, including 2x2 MIMO with single-polarisation antenna elements, 3x3 MIMO utilising a combination of a single polarisation antenna array and a dual-polarisation antenna array and 4x4 MIMO utilising two dual-polarisation antenna arrays (or sub-arrays).

Further details will be provided, below, in regard to a non-exhaustive range of possible antenna array configurations, which are configured to save space and cost relative to those just discussed in relation to Figure 3. These will be described in conjunction with Figure 19 to Figure 28 inclusive. Figure 4 shows a range of views of an idealised example of an antenna radiation pattern of the form discussed above in relation to Figure 3 : a pattern which is broader in one plane than it is in an orthogonal plane.

Figure 4(a) shows a wireframe representation of a top view of an idealised approximation of an antenna radiation pattern of a form which could emanate from a horizontally-oriented linear multi-element antenna array, such as that formed from antenna elements 301a, 301b, 301c and 30 Id in Figure 3(a). The view shown in Figure 4(a) is equivalent to looking from a vantage point above the plane 401 of antenna array 300 shown in Figure 3(a) or, in other words, the plane 401 of antenna array 300 could appear as a horizontal line, running from left to right across the page, as shown, below the radiation pattern shown in Figure 4(a). The view shown in this figure and, indeed, all of the parts of Figure 4 is idealised in that it shows a perfectly- symmetrical main lobe and no side-lobes. Whilst this is clearly not representative of a typical antenna radiation pattern, it serves to highlight a fundamental shape of a main lobe of an antenna radiation pattern and this will be used as an example, below, to illustrate the principles of a spatial location technique which may be realised with an access point and antenna structure of the form described herein. The implications of the inclusion of side-lobes within an antenna radiation pattern, and beneficial uses to which side-lobes, in conjunction with one or more main lobes may be put, are also discussed below. Figure 4(b) shows a wireframe representation of the side view of an idealised approximation of an antenna radiation pattern of a form which could emanate from a horizontally-oriented linear multi-element antenna array, such as that formed from antenna elements 301a, 301b, 301c and 301d in Figure 3(a). The view shown in Figure 4(b) is equivalent to looking from a vantage point to the left or right of a plane 401 of antenna array 300 shown in Figure 3(a) or, in other words, a plane 401 of antenna array 300 could appear as a vertical line, running from top to bottom down the page, as shown, to the left of the radiation pattern illustrated in Figure 4(b).

Figure 4(c) shows a wireframe representation of a front (boresight) view of an idealised approximation of an antenna radiation pattern of a form which could emanate from a horizontally-oriented linear multi-element antenna array such as that formed from antenna elements 301a, 301b, 301c and 301d in Figure 3(a). The view shown in Figure 4(c) is equivalent to looking from a vantage point in front of a plane 401 of antenna array 300 shown in Figure 3(a). It is clear from this view, in particular, that the shape of the beam, which consists purely of a main-lobe in this idealised example, is much larger in a vertical direction that it is in a horizontal direction. As a non-limiting example, the 3dB beamwidth of the main lobe shown in Figure 4 could be approximately 90 degrees in an elevation plane and perhaps 10 - 30 degrees in an azimuth plane. Figure 4(d) shows a wireframe representation three-dimensional view of an approximation of an idealised antenna radiation pattern of a form which would emanate from a horizontally-oriented linear multi-element antenna array; the viewpoint is taken from the rear and to the right-hand side of the antenna array, for example an array which could be formed from antenna elements 301a, 301b, 301c and 301d in Figure 3(a).

In one embodiment of a spatial location or geolocation system, independently formed and steerable beams emanating from an antenna array which is operably-coupled to an access point may be steered to enable communication with a UE and an intersection of two or more beams emanating from an antenna array which is operably-coupled to an access point, which may be the same access point, may be used wholly or in part to approximately spatially-locate a UE the signals emanating from which can be received by an access point.

In a second embodiment of a spatial location or geolocation system, independently formed and steered beams emanating from an access point may be steered to enable or minimise communication with a UE and an intersection of two or more regions of an antenna radiation pattern within which poor communications between a UE and an access point result, where two or more regions of an antenna radiation pattern emanate from an access point, which may be the same access point in both cases, may be used wholly or in part to approximately spatially-locate a UE which is in communication with an access point. Regions of an antenna radiation pattern within which poor communications between a UE and an access point may occur and as discussed above are sometimes referred to as 'nulls' in a radiation pattern.

In a third embodiment of a spatial location or geolocation system, independently formed and steered beams emanating from an access point may be steered and signal strength measurements may be made and stored of signals emanating from a UE during a steering or beam sweeping process to form a stored measured radiation pattern, with some or all of those stored signal strength measurements forming the stored radiation pattern being compared or correlated with one or more predetermined reference antenna radiation patterns in order to determine a steering angle or bearing at which a measured and a predetermined radiation pattern are most similar. This steering angle may then be reported as a bearing of a UE relative to a datum, such as a boresight direction of an antenna array forming part of a steerable antenna system or a plane of an antenna array forming part of a steerable antenna system.

In a fourth embodiment of a spatial location or geolocation system, independently formed and steered beams emanating from an access point may be steered and signal strength measurements may be made by a UE and stored of signals emanating from an access point and reported back to an access point by a UE during a steering or beam sweeping process to form a stored measured radiation pattern, with some or all of those stored signal strength measurements forming the stored radiation pattern being compared or correlated with one or more predetermined reference antenna radiation patterns in order to determine a steering angle or bearing at which a measured and a predetermined radiation pattern are most similar. This steering angle may then be reported as a bearing of a UE relative to a datum, such as a boresight direction of an antenna array forming part of a steerable antenna system or a plane of an antenna array forming part of a steerable antenna system. In still further variants of the first and second embodiments discussed above, signals to be measured could emanate from an access point which contains one or more steerable antennas with signal strength measurements being taken by a UE to be located, with that UE then reporting some or all of those signal strength measurements back to an access point. A peak or a null or any other identifiable beam pattern characteristic could then be identified by an access point within the measured data reported to it by a UE.

In both of the above embodiments, a UE need not be directly or indirectly associated with the access point or any access point, so long as any signals obeying a suitable protocol and occurring in an appropriate frequency range common to both UE and access point, are received by an access point from a UE. Alternatively signals obeying a suitable protocol and occurring in an appropriate frequency range common to both a UE and an access point may be transmitted by an access point and received by a UE, with a UE subsequently sending an acknowledgement back to an access point to indicate that reception of a signal or signals transmitted by an access point has been partially or wholly successfully achieved by a UE. Furthermore a UE may report back to an access point a measure of received signal strength, received signal quality or data rate. A UE is referred to as being associated with an access point where that UE is primarily or exclusively exchanging data with that access point and little or no data is being exchanged with other nearby access points, despite these other access points being within range of transmitter, receiver and antenna circuits of a UE.

Taking the first embodiment of a spatial location system discussed above, Figure 5(a) shows an example wireframe representation of a rear (boresight) view, looking away from an antenna array or arrays in a direction of propagation of electromagnetic waves radiating from the array or arrays, detailing an approximation of two intersecting antenna radiation patterns of a form which could emanate from a horizontally-oriented linear multi-element antenna array and a vertically-oriented linear multi-element antenna array, for example of the form shown in Figure 3(b) or Figure 3(d). Note that Figure 5(a) is intended to show a far-field view of an antenna radiation pattern such that the spatial separation of a horizontally-oriented linear multi-element antenna array and a vertically-oriented linear multi-element antenna array appears negligible and the resulting beam patterns appear to be emanating from the same point.

Figure 5(b) shows a detail view of an intersection of the wireframe representations of the radiation patterns illustrated in Figure 5(a), highlighting an approximately rectilinear area of intersection 501, shown by means of cross-hatched shading, and lines of constant relative antenna gain 502 and 503 which delineate this area of intersection. Lines of constant relative antenna gain 502 join together two separate loci of points at which the antenna array gain of a vertically-oriented antenna array (not shown), which is capable of generating elevation radiation pattern 504, are X dB below its peak antenna array gain at a given elevation angle from the boresight position of its main lobe, at the current azimuth bearing to which the antenna's main lobe is steered. Likewise, lines of constant relative antenna gain 503 join together two separate loci of points at which the antenna array gain of a horizontally-oriented antenna array (not shown), which is capable of generating azimuth radiation pattern 505, is Y dB below its peak antenna array gain at a given azimuth angle from the boresight position of its main lobe, at the current elevation altitude to which the antenna's main lobe is steered. In a typical embodiment, X may be equal to Y, although this need not be the case and should not be taken as a limiting example.

Take, for example, a horizontally-oriented first antenna array which is steered to a bearing of 10 degrees off boresight in azimuth (i.e. a plane in which its main-lobe is relatively narrow) and which has a main lobe with a peak gain of +10dBi at that beam position and a vertically-oriented (i.e. orthogonal to the first antenna array) second antenna array which is steered to a bearing of 15 degrees off boresight, in elevation (i.e. a plane in which its main-lobe is relatively narrow) and which has a main lobe with a peak gain of +8dBi at that beam position. With X and Y both set equal to say 1 dB for this example, a locus of points 502 would connect all points with a main-lobe gain of +9dBi for the horizontally-oriented first antenna and a locus of points 503 would connect all points with a main lobe gain of +7dBi for the vertically oriented second antenna, assuming that the approximately rectangular area of intersection 501 is sufficiently small that the variation in gain across this region, in the direction in which the main lobe is widest in each case, is negligible. This is a reasonable assumption for a beam shape, such as those discussed above, which is much wider in one plane than it is in an orthogonal plane. Lines of constant relative antenna gain 502 and 503 may represent, respectively, the resolution to which received signal strength can be measured by a receiver system connected to the antenna elements (not shown) which generate elevation 504 and azimuth 505 radiation patterns. In this case, approximately rectangular area of intersection 501 represents an area of uncertainty anywhere within which a UE could be located. In such a case, the centre of approximately rectangular area of intersection 501 could be computed and this could be assumed to be a location of the UE from which the signals emanate. This approach could have the benefit of minimising the average error resulting from reporting, separately or together, a spatial location coordinate set for of a large number of UEs for which the same received signal strength characteristics are obtained from a receiver system or systems connected to the antenna elements (not shown) which generate elevation 504 and azimuth 505 radiation patterns similar to those shown in Figure 5(a).

The above example assumed that a UE radiated a signal or signals which were then received by one or more steerable antenna arrays (or sub-arrays), which were swept in order to determine a region or regions of maximum received signal strength. It is equally possible for a UE to receive signals radiated by an access point equipped with one or more steerable antenna arrays (or sub-arrays), which were swept in order to permit a UE to measure a variation in received signal strength and report received signal strength readings back to the access point, thereby enabling the access point to identify a region or regions within which the UE experienced a maximum level of received signal strength.

Alternatively, lines of constant relative antenna gain 502 and 503 may represent worst-case error bounds for signal strength measurements made by a receiver system or systems connected to the antenna elements (not shown) which generate the elevation 504 and azimuth 505 radiation patterns shown in Figure 5(a). Such error bounds may be determined by the amount of noise present on the signal or signals received or could be determined by the dynamic characteristics of the environment in which the UEs are located, for example if the UEs are handheld devices and their users are moving around in a congested environment such as a shopping mall or a busy railway station. In a still further alternative possibility, lines of constant relative antenna gain 502 and 503 could represent worst-case data rate or signal quality bounds, such that a data rate or signal quality level of greater than a given threshold is achieved but a still greater data rate or signal quality level is unable to be achieved at that location. This option arises from the fact that, for example, Wi-Fi systems will typically 'negotiate' a data rate between one transceiver node and a second, distant, transceiver node, in 'steps' rather than as a continuous variation in data rate, based upon the signal strength received by each node and the interference level received at each node; note that the data rates need not be the same in both directions, since the levels of interference suffered by each node may be different due to their differing local radio environments. For a received signal incident at a particular point within an antenna's beam pattern a given data rate may be negotiated between its attached transceiver and a further transceiver from which the received signal emanated and, despite the antenna being capable of providing a slightly greater level of gain (and hence a slightly greater received signal strength) when using a slightly more optimal beam direction, the improvement in received signal strength at this beam direction may not be sufficient to allow the next higher 'step' in data rate to be sustained between the two nodes. Lines of constant relative antenna gain 502 and 503 could therefore alternatively represent separate loci of points at which the highest achievable data rate which can be maintained (however briefly) between the two nodes is achieved, with a yet higher gain beam position not being sufficiently better for the data rate to increase to the next-highest data rate step, for example going from 57.8Mbits/sec to 65Mbits/sec in the case of the IEEE 802.1 In standard.

Figure 5(c) indicates the orientations of azimuth and elevation in the above discussion of Figure 5. Figure 6(a) and Figure 6(b) show two views of a more realistic representation of an antenna beam pattern than did Figure 4(a) - (c). Figure 6(a) again shows a wireframe representation 600 of a top view of an approximation of an antenna radiation pattern of the form which would emanate from a horizontally-oriented linear multi-element antenna array, such as that formed from antenna elements 301a, 301b, 301c and 301d in Figure 3(a); it is thus a more realistic equivalent of Figure 4(a). The view shown in Figure 6(a) is equivalent to looking from a vantage point above the plane of the combined antenna array 300 shown in Figure 3(a) or, in other words, the plane of the combined antenna array 300 would appear as a horizontal line 606 (shown dashed), running from left to right, across the page, below the representation of the radiation pattern 600 shown in Figure 6(a). Wireframe representation 600 of a top view of an approximation of an antenna radiation pattern consists of main lobe 601, a left-hand side-lobe 602 and a right-hand side-lobe 603, together with a left-hand null 604 and a right-hand null 605. Left-hand null 604 and right-hand null 605 represent areas of the antenna's radiation pattern where the antenna possesses, locally, very low levels of antenna gain relative to those present at main lobe 601 or at side-lobes 602 and 603, such that the antenna radiates relatively low levels of electromagnetic radiation in those directions and will receive even strong signals incident from those directions relatively weakly, resulting in low RF signal levels being sent from the antenna's connector to any attached receiver circuits. Figure 6(b) shows a wireframe representation three-dimensional view of an approximation of an antenna radiation pattern of the form which would emanate from a horizontally-oriented linear multi-element antenna array with a two-dimensional, top- view, radiation pattern similar to that shown in Figure 6(a); the viewpoint is taken from a location looking from below and down upon the antenna array itself as if floating in space above the plane of the antenna array. The main lobe 601, side-lobes 602, 603 and nulls (e.g. 605) can clearly be seen in this view.

It is possible to steer or sweep, electronically, the example beam patterns shown in Figure 6(a) and Figure 6(b) in order to find a peak in signal strength, which could be the highest peak, or main lobe, a lower peak, or sidelobe, or one or other or both of the nulls. Sweeping a beam in this way, to locate a remote transceiver station or UE by means of locating one or more peaks in received signal strength, one or more nulls in received signal strength or a particular, known, pattern of peaks and nulls which may be used to identify whereabouts within the antenna's radiation pattern characteristic a UE is located, from measurements taken by either of the UE or the access point, is a key aspect of the present invention. Figure 7(a) shows a similar view to that of Figure 5(a) in that it shows a wireframe representation 700 of a rear (boresight) view, looking away from an antenna array or arrays in a direction of propagation of the electromagnetic waves radiating from the antenna array or arrays, detailing an approximation of two intersecting antenna radiation patterns of a form which could emanate from a horizontally-oriented linear multi-element antenna array and a vertically-oriented linear multi-element antenna array, for example of the form shown in Figure 3(b) or Figure 3(d). In the case of Figure 7(a), however, the approximately rectangular area of intersection 501 highlighted in Figure 5(b) has been replaced by an intersection of two separate loci of points 703, 704, representing a peak gain of an antenna array, in azimuth and elevation, as will now be described.

Locus 703 shows a line joining points representing roughly a peak value of gain, whether of a main-lobe or a side-lobe, of a horizontally-oriented antenna array (not shown), which is capable of generating azimuth radiation pattern 702 at a given azimuth angle from a boresight position of its main lobe or a side-lobe, at the current elevation altitude to which the antenna's main lobe or a side-lobe is steered. The antenna array could, for example, be formed using antenna elements 301a, 301b, 301c and 301d in Figure 3(a).

Locus 704 shows a line joining points representing roughly a peak value of gain, whether of a main-lobe or a side-lobe, of a vertically-oriented antenna array (not shown), which is capable of generating elevation radiation pattern 701 at a given elevation angle from the boresight position of its main lobe or a side-lobe, at the current azimuth bearing to which the antenna's main lobe or a side-lobe is steered. The antenna array could, for example, be formed using antenna elements 302a, 302b, 302c and 302d in Figure 3(a). If elevation radiation pattern 701 is steered in azimuth, i.e. left-to-right or right-to-left as viewed in Figure 7(a), and azimuth radiation pattern 702 is steered in elevation, i.e. top-to-bottom or bottom-to-top as viewed in Figure 7, independently, such that the peak gain of each is directed at a UE, then intersection 709 of locus 703 and locus 704, representing the peak gains in azimuth and elevation respectively, indicates an azimuth and elevation bearing respectively for the UE with respect to a datum based upon a feature of the antenna arrays (or sub-arrays), for example their un-steered boresight direction or a plane of one or both arrays. In this way, a UE may be located in two dimensions in space by reading or recording the bearings to which radiation patterns 701 and 702 are steered.

Figure 7(b) shows a similar situation to that of Figure 7(a), however in this instance azimuth radiation pattern 706 has been steered downward in elevation, such that an intersection 710 between locus 707 (analogous to locus 703 in Figure 7(a)) and locus 708 (analogous to locus 704 in Figure 7(a)) is now lower in elevation within the coverage area of the antenna arrays (or sub-arrays). Elevation radiation pattern 705 has not been moved in this example and resides at the same bearing and altitude as elevation radiation pattern 701 of Figure 7(a). Even in this instance, there is still an intersection of locus 707 and locus 708, which can indicate the location of a UE as described above in relation to locus 703 and locus 704, despite the absolute gain of an antenna array generating elevation radiation pattern 705 at this elevation altitude being likely to be lower than the level it would have exhibited with the beam locations shown in Figure 7(a).

Figure 8 illustrates an example of the operation of a beam-crossing technique for spatial location in two dimensions, based upon, for example, a ceiling-mounted antenna system. An antenna system (not shown) of the form described herein or of another form capable of generating independently-steerable beams operating in at least two planes and with differing beamwidths in each plane, is placed at location 801, for example mounted on a ceiling 802 of a room or building. The antenna system may generate two radiation patterns which each have a beam shape which is much wider in one plane than it is in an orthogonal plane, between, say, the -3dB points of the gain of the antenna arrays (or sub-arrays) relative to their peak gain values. A locus of points, termed a peak-gain locus, may be formed joining together points located in the wider plane of the beam pattern at which the gains achieved in the narrower plane of the beam pattern are at their peak values, at any given offset angle from boresight in the plane of the wider-beam. Note that the absolute gain level of these peak values will differ as the offset angle changes; the highest peak value will typically be achieved on boresight, with progressively lower values typically being achieved as the angular separation between the boresight angular location and the angular location under consideration, increases, up to the point where a side-lobe is reached.

A peak-gain locus for one example antenna main-lobe 804 and a second peak-gain locus for a second example antenna main-lobe 805 are shown in Figure 8. These two loci are illustrated in this figure based upon beams pointing almost directly downwards from ceiling 802, however it should be appreciated, from the preceding discussions, that these beams may be steered to any angle or angles in a plane which lies approximately perpendicular to a virtual planar surface defined by (or substantially enclosed by) their peak gain loci 804, 805, and which are within a steering capability of a beam-steering system and an antenna system. Loci 804 and 805 can be steered or 'swept' across area 803, which could be a floor area, for example, in order to locate signals from one or more UEs. As a peak gain locus sweeps across a UE, in response to beam-steering control from a beam-steering control system (e.g. control system 202 of Figure 2) a signal strength measured by a receiver system attached to a control system and the beam-steered antenna array or a signal strength measured by a receiver system within a UE to be located and which is reported back to a receiver system attached to a control system and the beam-steered antenna array, will typically increase and then, once a location of peak gain of the antenna has been passed, will typically decrease again. It is possible that either or both of the increasing or decreasing signal strength values just discussed will not be monotonic. This increase in measured signal strength followed by a decrease of measured signal strength, as the beam sweeps toward and then past a UE, may be used as input data to a control algorithm which may be used to steer an antenna beam, via a beam-steering control system (e.g. control system 202 of Figure 2) and a beamformer (e.g. 204 of Figure 2) to point a peak of the antenna's beam pattern (or gain characteristic) at a UE. Alternatively, the beam-steering angle at which a peak in received signal strength was recorded may simply be noted or reported, since this will typically represent an angle, in that particular plane, at which a UE is located. It may be necessary to repeat either or both of the above processes a number of times, in order to average the results or statistically process the results in some other way, in order to ameliorate the effects of noise, interference, or short-term changes in the environment, such as the movement of people or objects, upon the measured receive signal strength values.

The above process of sweeping a beam, as characterised by its peak gain locus, in a plane approximately perpendicular to a virtual surface defined by its said peak gain locus, may be carried out independently for two or more beams wherein at least two of the two or more beams are swept in non-identical (defined as non-parallel) planes. In the case illustrated in Figure 8, locus 804 defines a virtual surface, illustrated by vertical shading, and locus 805 defines a second virtual surface illustrated by horizontal shading (and which is only partially visible; it extends into the page to form a similarly-shaped virtual surface to that defined by locus 804). If the two example beams shown in Figure 8, are located at steering angles at which a UE, independently for each beam, yielded a peak value of received signal strength, then a point 806 at which the virtual planes defined by loci 804 and 805 cross and intersect a floor 803 (and assuming that a UE under consideration is located on or above that floor) is an approximate location of the UE, in two dimensions within the plane defined by floor 803.

Whilst the above discussion has concentrated upon loci defining the peak gain of a main beam, in a further embodiment it could equally apply to loci defining peak gains for one or more side-lobes of an antenna array radiation pattern. This may be advantageous in extending a range of angles over which a given spatial location system can operate, without having to alter the design of the antenna or beam-steering system, since side-lobes typically extend to much greater angles away from boresight than does a main lobe.

In a further, related, embodiment, it is possible to define loci which are based upon the or a minimum gain position or positions for an antenna when swept to search for a UE, for example gain or attenuation values which define and hence can locate nulls such as nulls 604 or 605 shown in Figure 6. In this case, the beam sweeping processes outlined above could search for, and record or otherwise highlight, beam angles at which a minimum of signal strength was measured at one or more receiving devices operably connected to the antenna array or arrays or reported by a UE back to a receiver and control system connected to the antenna array or arrays. An advantage of this 'null-searching' approach is that, as the nulls are typically sharply-defined and are typically more sharply-defined than beam peaks, whether main-lobes or side-lobes, the resulting angles recorded by the spatial location system may be more accurate than those recorded using a beam-peak searching methodology such as the example outlined above.

A yet further embodiment would combine both of the above approaches, searching for both nulls and peaks in an antenna array gain characteristics and recording both or all angles at which nulls and peaks occurred during the sweeping processes, optionally including those related to side-lobes. Given that the location of both peaks and nulls may be approximately determined either from the design of the system, simulations conducted on the designed system or field measurements conducted upon one or more (or all) samples of a manufactured or prototype system, then these known locations (offset angles) at which the various characteristics, whether peaks of nulls or some other characteristic, can be used to measure the beam-steering angles at which a UE or many UEs are located. Note that it is possible to uniquely spatially locate multiple UEs designed to operate with one or more of a wide range of radio systems, since transmissions to the said UEs are typically identified for, or directed at, each UE individually. For example, a given UE may have its own individual time-slot allocated in a time division multiple access system and transmissions to and from that UE will only or predominantly take place during that or those allocated time-slots. Thus it is possible to search for a beam-peak or a null or both for a particular UE during one or more time-slots allocated to that UE. Similarly, it is possible to search for beam-peaks or nulls on frequencies allocated, uniquely for a period, to a given UE or to codes in a CDMA system, allocated to a particular UE or by any other mechanism by which transmissions to or from a UE can be uniquely identified.

Figure 9 illustrates a further example 900 of the operation of a beam-crossing technique for spatial location in two dimensions, based upon an antenna system (not shown) or a complete access point (not shown) containing an antenna system placed at a location 904 which is high-up on a wall 903 close to or adjoining a ceiling 901 and subtending an angle to the ceiling 901 which is between -0.1 degrees and -90 degrees, in other words, pointing at least partially in a downward direction toward a floor 902. An antenna system (not shown) of a form described herein or of another form capable of generating independently-steerable beams operating in at least two planes, is placed at location 904, as just described, for example mounted using an angled bracket on a ceiling 901 or a wall 903 of a room or building. The antenna system may generate two radiation patterns which each have a beam shape which is much wider in one plane than it is in an orthogonal plane, between, say, the -3dB points of the gain of the antenna arrays (or sub-arrays) relative to their peak gain values. A locus of points, termed a peak-gain locus, may be formed as described above in relation to Figure 8 joining together points located in the wider plane of the beam pattern at which gain levels achieved in the narrower plane of the beam pattern are at their peak values, at any given offset angle from boresight in the plane of the wider-beam.

The operation of the system illustrated in Figure 9 is similar to that of the system illustrated in Figure 8 with the beam-patterns shown being illustrated in a similar manner, based upon peak-gain loci. The beam patterns shown in Figure 9 may be steered or swept using one or more control systems and one or more beamforming systems as discussed in relation to Figure 8. An intersection 906 of beams or particular parts of beams or a locus of points on beams, based upon, say, a locus of peak gain values of one or more of the beams in a plane in which the beamwidth of the antenna main lobe is at its narrowest, may be used to indicate a likely two- dimensional spatial position of a UE with which the access point to which the antenna array or arrays is connected, is in communication.

The pointing angle at which an access point or antenna array is mounted, in the example deployment scenario illustrated in Figure 9, is instrumental in determining the coverage which can be achieved from that array or access point and is a partial determinant of spatial location accuracy, particularly for UE which are more distant from the access point or antenna array. For example, consider an antenna array which can be steered in elevation over an angular range of +/- 45 degrees from boresight, where boresight is assumed to be perpendicular to the plane of the array in two dimensions, and which has a useful beamwidth, in the plane of its widest beam, of say 90 degrees, where its useful beamwidth can be defined as the angular range over which the beam is able to satisfactorily communicate with a UE (which may well not be the same as its -3dB beamwidth, for example). If this array is mounted at a position 904 which is adjacent to a wall 903 and a ceiling 901 and angled pointing downward at 45 degrees to the horizontal (e.g. the ceiling), then the array will be capable of satisfactorily covering most or all points between wall 903 and ceiling 901 within an angular range of +/-45 degrees to the wall in a horizontal plane. If the array is mounted at a greater angle to the horizontal of say 50 or 60 degrees, then the range of coverage of the antenna array or access point is likely to be reduced, as the beam is pointed more toward the floor 902, however, the location accuracy may increase in this scenario, since each beam-steering angular digital 'step' will correspond to a smaller distance when considering more distant UEs.

It will be obvious to those skilled in the art that various other mounting locations for an antenna array or arrays or an access point containing an antenna array or arrays are possible whilst not detracting from the principles of operation of the invention described herein. For example, such a system could be mounted at any point and positioned at any angle on a wall, on a ceiling, in a corner, on a sloping ceiling such as are commonly found in stairwells, on a gantry, beam or other support structure or on, in, above or below any other suitable mounting location which is appropriate to permit the radiation of signals over a desired coverage area, based upon the available steering range of the antenna system.

Figure 10 illustrates a similar example scenario to Figure 9, however in this case, the shaded surfaces and locus lines have been removed from the diagram, for clarity, and only the beam intersections are illustrated. Access point 1004 is mounted at an angle to the ceiling 1001 and on or close to a wall 1003. A locus of an intersection 1005 between at least two beams intersects a floor 1002 at intersection 1006. Assuming that the at least two beams are directed at a UE at known positions in their beam characteristics (e.g. at peaks of their main lobes), then a spatial location of the UE can be derived as being at, or close to, intersection 1006. Figure 11 illustrates one example mechanism by which a UE may be located by means of switching or sweeping an antenna beam 1103 between two or more positions (with only two positions being illustrated in Figure 11(a) and Figure 11(b)). Consider, first, Figure 11(a). A User in possession of a UE is located at an angle to the plane of the antenna array 1104 shown by means of a dashed line 1101 ; in this example the UE can be seen to be located at an angle of approximately 90 degrees to the plane of the antenna array (and approximately on boresight for the antenna array as shown). In Figure 11(a), an antenna beam 1103 can be seen to have been switched or steered to the left of boresight, in this case by approximately 15 degrees, although any other steering angle could be chosen. At this steering angle, a received signal level, illustrated by dashed line 1102a can be measured at a receiver connected to the antenna array.

In Figure 11(b), antenna beam 1103 can be seen to have been steered to the right of boresight, in this case by approximately 10 degrees, although here, again, any steering angle could have been chosen. At this new steering angle, a new received signal level, illustrated by dashed line 1102b can be measured at a receiver connected to the antenna array. A difference in measured received signal strength amplitudes, AA, between the two received signal strength measurements taken at each of the two beam positions, provides an indication of the beam-steering error of the antenna's main lobe with respect to the location of the UE. If the main lobe of the antenna (for example antenna beam 1103) is assumed to be symmetrical about its point of peak or maximum gain, then a non-zero value for ΔΑ indicates that the beam has been switched between two positions which are not equally located on either side of the angular location at which the UE is positioned. In the case shown in Figure 11, the beam position illustrated in Figure 11(b) is closer to the angular position of the UE and this will be evident by the fact that the signal strength amplitude 1102b measured at the illustrated beam angle in Figure 11(b) will typically be higher than a corresponding signal strength amplitude 1102a measured at the illustrated beam angle in Figure 11(a). A new beam position can now be tried, for example to the left of boresight, with the difference between the new position and the original left-of-boresight position illustrated in Figure 11(a) typically being determined, at least partially, by the size of the value of ΔΑ; a large value of ΔΑ would typically indicate that there is a gross error in the original left-of-boresight beam position and hence a large change in position is needed, whilst a small value of ΔΑ would typically indicate that there is a smaller error in the original left-of-boresight beam position and hence a small change in position is needed. In this way, the value of ΔΑ can be progressively reduced by attempting and refining steering angles for antenna beam 1103. Once ΔΑ has been reduced to an acceptable level, the two beam positions which result in this small value, with one being to the left of boresight and one being to the right of boresight, provide two angular measurements (steering angles for antenna beam 1103) which are approximately equidistant, in an angular sense, from the angular location 1101 of a UE. The angular location of the UE can then be calculated by taking, for example, the lower beam angle, say to the left of boresight and adding to it half of the difference between the lower beam angle and the higher beam angle.

Taking the values given above of a first steering angle of -15 degrees relative to boresight (where boresight is defined as being notionally at an angle of 90 degrees to the plane of the antenna array) or 75 degrees relative to the plane of the antenna array and a second steering angle of +10 degrees relative to boresight (i.e. to the right of boresight) or 100 degrees relative to the plane of the antenna array, the first steering angle would be reduced from -15 to -10 degrees (i.e. from 75 degrees to 80 degrees) in one or more steps, to reduce ΔΑ to approximately zero and thereby form a third steering angle (which would equal -10 degrees relative to boresight or 80 degrees relative to the plane of the antenna array). This would result in a difference between the two steering angles of 100 - 80 = 20 degrees, with half of this value being 10 degrees. Adding this to the lower beam angle (80 degrees) gives 80 + 10 = 90 degrees as the angular location of the UE, which corresponds to the situation illustrated in Figure 11.

Figure 12 shows a flow-chart representation of the UE angular location method described above. The method begins at step 1201 and at step 1202 an estimated initial beam angle is chosen which is somewhat to one side, say to the left side, of an expected approximate location of the UE and a beam is steered to that angle. At step 1203 a first received signal strength of a signal received from the UE is measured by a receiver connected to the antenna array and both the beam angle at which the measurement takes place and the corresponding received signal strength measurement are stored in store 1204.

At step 1205, a second estimated initial beam angle is chosen which is somewhat to the other side, say to the right side, of an expected approximate location of the UE and a beam is steered to that new angle. At step 1206 a second received signal strength of a signal received from the UE is measured by a receiver connected to the antenna array and both the beam angle at which the measurement takes place and the corresponding received signal strength measurement are again stored in store 1204.

At step 1207 the first and second signal strength values are retrieved from store 1204 and the absolute value of a difference, ΔΑ, between the signal strength values is calculated, for example by subtracting the first signal strength value from the second signal strength value and calculating the modulus of the result, yielding |ΔΑ|. At decision step 1208, a difference, |ΔΑ|, between the signal strength values is compared to a threshold, T, where T is typically a small positive number and may be close to zero.

If the result of the comparison undertaken in step 1208 is that |ΔΑ| is not less than threshold T, then the method moves to step 1210. If, on the other hand, the result of this comparison is that |ΔΑ| is less than threshold T, then the method moves to step 1209. Step 1210 is only undertaken in the event that the difference between the first and second signal strength values, |ΔΑ|, is not sufficiently small for the method to continue to step 1209. In step 1210, a new value is chosen or calculated for a second estimated beam angle which is chosen to be to the same side, say to the right side, of an expected approximate location of the UE as was the original second estimated initial beam angle and a beam is then steered to the new angle. The method then continues with step 1206 and so on, as discussed above. Note that the amplitude value then measured in step 1206 and the corresponding beam angle value may, in one embodiment, be appended to store 1204 or may, in a second embodiment, over-write the originally stored values retained in store 1204 and which were derived at the original second estimated initial beam angle. At the point at which the result of the comparison step 1208 is that |ΔΑ| is less than threshold T, then the method moves to step 1209, as discussed above. At step 1209, the angular difference between the first estimated beam angle value and the second estimated beam angle value (or the latest version of the second estimated beam angle, in the event that a number of iterations are required in order for the comparison undertaken in step 1208 to become true) is calculated and approximately one half of this difference is added to the numerically lower valued beam angle, resulting in an estimated UE angular bearing relative to the plane of the antenna array. The resulting estimated UE angular bearing is then reported in step 1211 and the method ends at step 1212. The method could, of course, be repeated as often as is required to continue to track a UE which is, or may be, in motion within the coverage area of the access point or antenna system.

In a further embodiment, the method could operate with signal strength values reported to the method by a UE rather than values measured by an access point and reported to the method. In this further embodiment, the access point would operate as a signal source and the beam would be switched or swept as described above, with the UE measuring the signal level it received at each step and reporting these signal levels back to the access point which was executing the method.

Consider now a complete spatial location system, consisting of two or more antenna arrays (or sub-arrays) which are together capable of generating at least two non- parallel antenna patterns which are wider in one plane than they are in an orthogonal plane. In one embodiment of a spatial location system according to the present invention, the algorithm described above with reference to Figure 11 and Figure 12 or any other suitable algorithm or algorithms may be utilised independently or together to provide an angular location, relative to boresight or any other datum, of one or more UEs in two or more separate planes utilising two or more separate antenna arrays or sub-arrays or two or more polarisations from one or more separate antenna arrays. In this way, at least two angular locations for the UE may be derived, in non- parallel planes and the intersection of these planes at the point or points identified by each algorithm, or each execution of the same or a similar algorithm, may then be used to estimate the location of the UE in at least two dimensions. An alternative embodiment of a method for spatially-locating a UE will be described below with reference to Figure 13 and Figure 14. In simple terms, an antenna beam or beam pattern which has one or more lobes which are broader in one plane than in an approximately orthogonal plane, such as the form of beam pattern shown in Figure 6(a) and Figure 6(b), may be 'swept' in the plane of its narrowest lobe or lobes. This can be imagined as the antenna pattern of Figure 6(a), being swept about a point at which it nominally emanates from a plane of its associated antenna array. Figure 13(a), (b), (c) and (d) illustrates four different example 'snapshots' of the beam pattern of Figure 6(a) as it is swept from left to right, covering a bearing angle from Bl degrees through B2 and B3 degrees to B4 degrees from the plane of the antenna array 1304. In this example scenario, Bl and B4 are approximately equal, however any two angles which are both within the capabilities of the antenna array to sweep (in conjunction with an associated beamformer and control system) and which cover the required area within which spatial location is desired, could be chosen. Figure 13(a) shows an example antenna beam pattern 1300 with a main-lobe 1303 which has been steered to an initial bearing 1307 which is at an angle Bl to the plane of an antenna array 1304. The approximate centre point about which the antenna array's beam may be steered 1305 is shown close to the centre of the antenna array 1304, however it could be located at any point within or possibly also outside of the array, depending upon the design of the array and the composition of the various signals feeding the elements. The antenna array 1304 is connected to a beamformer (not shown) and a control system (not shown), forming a beam-steering system, as described earlier in this disclosure or any other form of beam control, switching, sweeping or steering system, for the purposes of allowing the antenna array's beam pattern to be swept, electronically, across most or all beam angles commensurate with the resolution or beam-step size of the beam-steering system and which fall within the capability of the design of the antenna array 1304 and its associated beam-steering system.

At initial bearing 1307 for a main lobe of a beam-steered antenna array and considering a bearing 1301 for a UE which is to be located, a signal strength level 1302a could be measured at a receiver attached to the beam-steered antenna array. Note that at initial bearing 1307 the UE would be received using a right-hand side- lobe 1308 resulting in a comparatively high signal strength being recorded at the receiver, considering how far, in angular terms, the UE is away from being received by the main lobe 1303 of the antenna array. The main lobe of the beam-steered antenna array may be swept, electronically (i.e. with little or no physical or mechanical movement of the antenna array or its constituent parts) clockwise in the direction of the dotted-line arrow 1306. This is not, however, a limiting example, and the main lobe of the beam-steered antenna array could equally well begin at a different angle to the plane of the antenna array 1304 and be swept in an anticlockwise direction. Figure 13(b) shows an example of an antenna beam pattern part- way through a sweep from initial bearing 1307 to final bearing 1312 (final bearing 1312 is shown in Figure 13(d) and discussed further below). In Figure 13(b), a main lobe of the antenna array 1304 has reached first interim bearing 1309 which occurs at an angle B2 to the plane of the antenna array 1304. At this beam position a UE to be located which is placed at a bearing 1301 (as before) would appear close to a minimum (a minimum antenna array gain value) of the antenna beam pattern, in between main lobe 1303 and right- hand side-lobe 1308. Signal strength level 1302b, which in this example would be somewhat lower than signal strength level 1302a discussed above, could be measured at a receiver attached to the beam-steered antenna array. Figure 13(c) shows a further example of an antenna beam pattern part- way through a sweep from initial bearing 1307 to final bearing 1312 (final bearing 1312 is shown in Figure 13(d) and discussed further below). In Figure 13(c), a main lobe of the antenna array 1304 has reached second interim bearing 1310 which occurs at an angle B3 to the plane of the antenna array 1304. At this beam position a UE to be located which is placed at a bearing 1301 (as before) would appear part- way down left-hand side-lobe 1311 of the antenna beam pattern, in between main lobe 1303 and left-hand side-lobe 1311. Signal strength level 1302c, which in this example would be somewhat higher than signal strength level 1302b but still lower than signal strength level 1302a, could be measured at a receiver attached to the beam-steered antenna array. Figure 13(d) shows a still further example of an antenna beam pattern during a sweep from initial bearing 1307 to final bearing 1312. In Figure 13(d), a main lobe of the antenna array 1304 has reached final bearing 1312 which occurs at an angle B4 to the plane of the antenna array 1304. At this beam position a UE to be located which is placed at a bearing 1301 (as before) would appear close to the top (higher antenna array gain value) of left-hand side-lobe 1311. Signal strength level 1302d, which in this example would be somewhat higher than signal strength level 1302c and potentially similar to signal strength level 1302a discussed above, could be measured at a receiver attached to the beam-steered antenna array.

In the example described above in relation to Figure 13(a) - (d), four signal strength values 1302a, 1302b, 1302c and 1302d are obtained for the UE, at the four different bearings shown. These values can be seen to vary according to the point within the antenna's beam pattern at which the UE's signal appears; the UE is assumed not to have moved during the sweeping process or to have moved by a negligible amount in relation to the accuracy required of the spatial positioning system and hence this variation is largely or wholly due to the shape of the antenna array's beam characteristics as its beam pattern is 'swept past' the quasi-static UE (for example in the direction of arrow 1306). The UE can be considered to be quasi static in most implementations of an electronic beam-sweeping or steering system, since the rate of change of angle of the electronic beam-steering antenna system is typically much faster than the likely rate of change of angle subtended by a moving (e.g. walking) user and associated UE. If a UE is assumed to be quasi-static, the sweeping process and its resultant changes in received signal strength as measured at a receiver connected to a beam-steerable antenna array, can approximately reproduce a radiation pattern (or beam pattern) of a beam-steerable antenna array, in much the same way as would be obtained from an antenna measurement range or system which is capable of two-dimensional antenna radiation pattern measurements.

For example, as a peak of a beam-steerable antenna array's radiation pattern sweeps past a bearing at which a UE is located, a received signal strength as measured at a receiver connected to the array's output terminals would typically initially increase, then peak and finally decrease as a lobe (either a main lobe or a side-lobe) of the antenna's radiation pattern encounters and then passes a bearing at which a UE is located. Likewise, as a null in a beam-steerable antenna array's radiation pattern sweeps past a bearing at which a UE is located, a received signal strength as measured at a receiver connected to the array's output terminals could initially decrease, then reach a minimum and finally increase as a null (for example between a main lobe and a side-lobe) of the antenna's radiation pattern encounters and then passes a bearing at which a UE is located. Values of received signal strength obtained during the above sweep or sweeps may be recorded and then analysed to locate either or both of peaks or nulls in the signal strength values obtained. Since angular locations of these peaks and nulls of the antenna radiation pattern derived from received signal strength measurements from or by a UE are therefore known and the angles from boresight or the plane of the beam- forming antenna array (or any other fixed reference point) at which such peaks or nulls would be expected to occur relative to a known datum (for example the boresight direction of the antenna array) are also known, for example from design simulations of the antenna array or from measurements conducted upon one or more prototypes of the antenna array, it is possible to relate the angular locations of the peaks or nulls (or both) obtained in the beam-sweeping process to the measured or simulated locations of those peaks or nulls (or both) from the original antenna design or prototype. For example, if the highest value of received signal strength received during a complete sweep of the antenna, whilst searching for a UE, is obtained whilst the highest-gain point ('peak') of the main lobe is at a main lobe bearing of say 80 degrees from the plane of the antenna array, then it follows that the UE is located at a bearing of approximately 80 degrees from the plane of the antenna array. The relationship between a bearing at which a gain of a main lobe reaches its highest value and a corresponding beam-steering angle set by a controller and stored in conjunction with a signal strength measurement taken at this beam-steering angle may be derived from, for example, design simulations or measurements conducted on one or more prototype beam-steering antenna systems.

Alternatively (or additionally), if a lowest value of received signal strength received during a complete sweep of a beam-steering antenna array, whilst searching for a UE, is obtained whilst the lowest-gain point (i.e. deepest null) of its radiation characteristic is at a bearing of say 60 degrees from a plane of the antenna array, then it follows that the UE is located at a bearing of approximately 60 degrees from a plane of the antenna array; the relationship between a bearing at which a gain of a beam-steering antenna system reaches its lowest value and a beam-steering angle set by a controller and stored in conjunction with a corresponding signal strength measurement may be derived from, for example, design simulations or measurements conducted on one or more prototype beam-steering antenna systems. A sweep of an antenna beam such as that illustrated in Figure 13(a) - (d) can also, typically, be reversed once partially or wholly undertaken, in order to return a main lobe of a beam-steered antenna array to initial bearing 1307 or to any other prior angle. Alternatively, sweeping could commence from final bearing 1312 in Figure 13(d) with a direction of sweep opposite to that shown by dotted-line arrow 1306 in Figure 13(a). Indeed, sweeping could begin at any point and end at any point and proceed in either a clockwise or an anti-clockwise direction (based upon the orientation of the beam-pattern shown in Figure 13) and even change direction one or more times within a given sweep, in order to gain additional receive signal strength measurement data for one or more particular areas of interest, in order to facilitate averaging of the received signal strength values obtained, for example.

Whilst the above examples have described searching for either a highest gain point of an antenna array or a lowest gain point of an antenna array, it is possible to search for other gain values or, more powerfully, for known sequences of gain values, based upon their correlation with changes in measured received signal strength values. For example, it is possible to search for a sequence of signal strength values which increase rapidly, then more slowly to a peak, before decreasing slowly and then more rapidly to a low level; this would clearly indicate a lobe in an antenna pattern and if the angular 'width' of this lobe matched a known width of a main lobe, then it would be clear in which direction a UE was located, based upon the angular location of a peak value calculated (or predicted) for this lobe. Note that it would not be necessary to obtain a signal strength measurement at the absolute peak of this lobe, the location of the peak could be inferred by calculation, based upon a known (previously measured) shape of the lobe, by means of a pattern-recognition, correlation or curve- fitting algorithm, as is known in the art. The above discussion was based upon the angular location of a UE by a single steerable antenna array; clearly this will result in a quasi-linear locus of possible UE locations, for the reasons discussed above in relation to Figure 5 to Figure 10. The same or a similar beam-sweeping process just described may also be applied to a second, independent, orthogonal steerable antenna array and a second, orthogonal, angular location of a UE may be obtained, typically simultaneously with the first. Again this second angular location will result in a quasi-linear locus of possible UE locations, when considered in isolation. If, however the two loci, one obtained from a first steerable antenna array and another from a second, orthogonal (or at least non- parallel), steerable antenna array, are intersected, then a point of intersection can typically provide a single, accurate, location for a UE. Figure 14 shows a flowchart representation of a 'peak-search' method of locating a UE, of a form discussed above. The method starts at step 1401 and continues to step 1402 in which an antenna beam is steered or switched to a starting position (angle), for example a position similar to that illustrated in Figure 13(a) or any other suitable position. The method then moves to step 1403 in which a signal strength level at the current beam position is measured by a receiver connected to the antenna array or by any other suitable means; a measured signal strength value and an associated beam position angle at which it was measured are both stored in memory store 1404.

The method then moves on to decision step 1405 in which the current beam position (angle) is checked to see if it is the intended final beam position for a given beam sweep. If so, the method moves on to step 1407; if not, then further beam positions are required within the sweep and the method moves to step 1406. In step 1406, the current beam position (angle) is incremented to the next step in the sweep. The step size used is typically a fraction of a degree, for example one-tenth of a degree or one- quarter of a degree, although any suitable step size may be chosen. Once the beam's position has been incremented, the method resumes at step 1403 where a signal strength obtained at that beam position is measured and recorded, as described above. Again the current beam position (angle) is checked, in decision step 1405, to see if it is the intended final beam position for a given beam sweep and if so, the method moves to step 1407. In step 1407 the signal strength data retained in store 1404 is analysed to find the highest value of signal strength recorded during a complete sweep from the starting position to the final (or end) position. In step 1408 the beam position (angle) at which this highest value of signal strength was recorded is reported as an approximate angular location or bearing of a UE in a plane in which the antenna's beam pattern was swept, relative to a datum set for the system, for example a plane of the antenna array or boresight for a main-lobe of the antenna array, assuming that a peak gain of the main lobe occurs in a boresight direction of the antenna array or at a known offset which can be corrected for in the reporting process. The method ends at step 1409.

Figure 15 shows a flowchart representation of a 'null-search' method of locating a UE, also discussed above. The method starts at step 1501 and continues to step 1502 in which an antenna beam is steered or switched to a starting position (angle), for example a position similar to that illustrated in Figure 13(a) or any other suitable position. The method then moves to step 1503 in which a signal strength level at the current beam position is measured by a receiver connected to the antenna array or by any other suitable means; a measured signal strength value and an associated beam position angle at which it was measured are both stored in memory store 1504.

The method then moves on to decision step 1505 in which the current beam position (angle) is checked to see if it is the intended final beam position for a given beam sweep. If so, the method moves on to step 1507; if not, then further beam positions are required within the sweep and the method moves to step 1506. In step 1506, the current beam position (angle) is incremented to the next step in the sweep. The step size used is typically a fraction of a degree, for example one-tenth of a degree or one- quarter of a degree, although any suitable step size may be chosen (including nonlinear step sizes). Once the beam's position has been incremented, the method resumes at step 1503 where a signal strength obtained at that beam position is again measured and recorded, as described above. Again the current beam position (angle) is checked, in decision step 1505, to see if it is the intended final beam position for a given beam sweep and if so, the method moves to step 1507.

In step 1507 the signal strength data retained in store 1504 is analysed to find the lowest value of signal strength recorded during a complete sweep from a starting position to a final (or end) position. In step 1508 a known angular difference between the deepest null (i.e. the position of minimum antenna gain within the antenna array's radiation pattern) and the antenna's datum point (e.g. a plane of the antenna array or a boresight direction of the antenna array) is used to calculate an angle at which a UE is likely to be located relative to the antenna's datum point. In step 1509, an angle calculated in step 1508 is reported as an approximate angular location or bearing of a UE in a plane in which the antenna's beam pattern was swept. The method ends at step 1509.

The graphical representations of the antenna radiation patterns (or beam patterns) discussed above in this disclosure, for example those shown in Figure 6, Figure 11 and Figure 13 have all been plotted utilising a polar co-ordinate system as this provides a good visualisation of the antenna array as a quasi-point source (when considering, in particular, the far-field radiation of the antenna) and a good indication of how the electromagnetic energy radiated by the antenna array spreads out into its coverage space. It is possible, however, to plot an antenna's characteristics in a Cartesian form, such as is illustrated in Figure 16(a) and this form of visualisation can be useful when accurately comparing antenna pattern characteristics. Comparing antenna pattern characteristics from a known characteristic, for example one obtained on an antenna measurement range, with an antenna beam when fixed (un-steered) such that its main- lobe is located in an antenna boresight direction or steered such that its main-lobe is located in an antenna boresight direction, with one obtained from a UE in an active, deployed, system can enable an angular location of a UE to be determined, as will be discussed below with reference to Figure 16.

In Figure 16(a), the horizontal axis shows an angular position measured in degrees relative to a boresight position of an antenna array and the vertical axis shows a gain, typically expressed in dB, of an antenna array relative to a reference level of gain, where the reference level of gain is typically chosen as an ideal isotropic radiating element, resulting in a gain expressed in units of dBi. Note that the antenna radiation pattern shown in Figure 16(a) is that measured from a real physical example of a four- element antenna array which has been constructed and then measured using an antenna measurement range, with the results being quantised to a minimum of ldB steps which is similar to the signal strength measurement resolution of a typical receiver located in a Wi-Fi access point; Figure 6, Figure 11 and Figure 13, in contrast, showed idealised approximations of one or more antenna array radiation patterns.

Figure 16(b) shows a Cartesian representation of a steered antenna array radiation pattern, with its horizontal axis showing the angle in degrees relative to an un-steered boresight direction for the antenna array, where the un-steered boresight direction is zero degrees and its vertical axis shows the antenna's gain in dBi. The antenna radiation pattern shown in Figure 16(b) is a modified version of the antenna radiation pattern shown in Figure 16(a). This radiation pattern is taken from the same antenna array, however it has been modified in three ways: firstly, the resolution of the measurement system has been artificially reduced to a step size of ldB to correspond to a typical resolution of a received signal strength measurement in a low-cost receiver system, such as that present in a typical Wi-Fi access point; secondly, the radiation pattern has been shifted such that the main-lobe peak now no longer corresponds to the original boresight position, with this new position corresponding to the situation where the signal being received is not located at the un-steered boresight location of a steerable antenna array but at a new position offset from the un-steered boresight position of the array; thirdly, the pattern has been modified in a manner typical of what could happen in a 'real-world' environment, such as within a building or in a plaza surrounded by buildings. Such modifications could include a reduction in the depth of the 'nulls' in the radiation pattern and an increase in the size of side-lobes and the addition of further side-lobes all of which can result from, for example, signal reflections from surrounding structures or vehicles. In other words, as can be seen in Figure 16(b), the pattern is now somewhat different to the more 'ideal' pattern shown in Figure 16(a), although even this pattern is far from perfect, in that it is not symmetrical about its boresight angle and nor does it have especially low side-lobe levels.

The example beam pattern shown in Figure 16(b) represents a swept measurement undertaken upon a UE which is positioned approximately 20 degrees away from an un-steered boresight of a steerable antenna system and when limited to a resolution of ldB for a received signal strength measurement employed in a receiver used for taking the measurement. A receiver used to make this measurement would typically form a part of a Wi-Fi access point, cellular communications receiver, public safety communications receiver or other radio communications receiver. Whilst the example beam pattern shown in Figure 16(b) has been measured using the same angular resolution and the same signal strength resolution as that of the reference antenna measurement, shown in Figure 16(a), this need not be the case. Indeed in a typical scenario, a coarse estimate of the location of the UE may be made utilising a relatively small number of measurements taken at relatively widely spaced angles, for example measurements taken every 10 degrees over a range of +/-50 degrees from the un- steered boresight direction. The use of a correlation based technique, as will be discussed, enables a useful measure of geolocation to be achieved even from a relatively sparse set of data such as may be obtained when using a coarse angle step size.

The example reference antenna characteristic shown in Figure 16(a) and the example deployed antenna characteristic obtained, for example, from measurements of signal strength from a UE located within a coverage area of the antenna system and shown in Figure 16(b), may be compared in order to determine the angular separation of the UE from the antenna's boresight position. One example of a means by which such a comparison may be undertaken is that of correlation. In one example of a correlation process, known as sliding correlation, one data set, say a reference antenna characteristic data set, is successively multiplied with a second data set, say that of a deployed antenna characteristic obtained from measurements of a UE to be located by the system. This successive multiplication may be achieved as illustrated in the following non-limiting example. A first example data set, Data Set #1, has 100 pairs of values, with each pair consisting of, for example, a beam angle relative to boresight and a corresponding normalised measure of signal strength, and a second example data set, Data Set #2, also has 100 pairs of values with each pair again consisting of, for example, a beam angle relative to boresight and a corresponding normalised measure of signal strength. The first data set could consist of beam angles and corresponding normalised measurement values of signal strength measured in a controlled environment, such as antenna measurement range, and the second data set could consist of beam angles and corresponding normalised measurement values taken of the signal strength obtained from or by a UE in a deployed geolocation system. The normalised values in each case may be normalised with reference to the peak value of signal strength obtained from a given sweep of an antenna beam from one extreme of its coverage range to an opposite extreme of its coverage range. Whilst normalisation would typically be undertaken it is not essential to the correct functioning of the correlation technique described herein. Each data set may then be appended with further null (zero) values such that during a sliding correlation process, when a valid data set value is multiplied with a null value (zero), the result is zero.

Data Set #1 may now be aligned with Data Set #2 such that none of the valid data points overlaps, i.e. that the highest numbered data point (point 100 in this example) of Data Set #1 is aligned with one data point location below the lowest numbered data point (point 0 in this example) of Data Set #2. In other words, Data Set #1 occupies data point locations -99 to zero and Data Set #2 occupies locations 1 to 100 with data point locations -99 to zero and data point locations 101 to 200 of Data Set #2 being set to zero and data point locations -199 to -100 and 1 to 100 of Data Set #1 being set to zero. Each normalised signal strength value at each data point location is then multiplied individually for example a signal strength value from Data Set #2 stored at data point location 1 would be multiplied with a signal strength value from Data Set #1 stored at data point location 1 and so on for all data point locations from 1 to 100 in this example. The results of these individually multiplied signal strength values are then added together to form a single result and this is assigned to a Correlation Data Set data point location 1. One data set is then shifted by one data point location, such that the valid (non-zero) data now begins to overlap and the process is repeated. In the above example, the pairs of values of angular separation from boresight and their corresponding normalised signal strength levels of Data Set #1 are moved such that a pair of values originally stored at data point location 1 would now be stored at data point location 2 and a pair of values originally stored at data point location 2 would now be stored at data point location 3 and so on for all of the values stored, with each normalised signal strength value from Data Set #1 then being multiplied with its corresponding normalised signal strength value from Data Set #2 and all resulting multiplied values summed with the summed result being stored at Correlation Data Set data point location 2. This process is then repeated for all values, i.e. it would be repeated a total of 100 times in this example. Since each data point location corresponds to an angular position, typically defined relative to the antenna's boresight pointing angle, it is possible to relate the Correlation Data Set directly to an angular position relative to boresight and a graph may then be plotted of the value of the correlation result, at each angular location, as one data set progressively slides across the other, in this case as Data Set #1 slides across Data Set #2. A typical form of the resulting characteristic is shown in Figure 16(c), in which the horizontal axis shows an angular position relative to a boresight position of the antenna array and the vertical axis shows a relative correlation value, with a peak correlation corresponding to a correlation value of one. It can be seen from this figure that a large and distinct peak occurs in the characteristic at an angular offset from boresight at which the centre of the highest signal strength peak occurs in Figure 16(b), even though the limited resolution of the signal strength measurements used (ldB) means that a number of adjacent angular measurements all result in the same value of peak signal strength, thus making it more difficult to ascertain precisely where the UE is located purely on the basis of peak signal strength. The angular location of the correlation peak typically provides a clear, single, angular location for a UE, despite the apparent distortions to an antenna's radiation characteristics which result from reflections and other practical effects when an antenna system is deployed in a cluttered environment. It is thus a very powerful angular geolocation tool. Figure 17 illustrates a method for calculating the angular location of a UE relative to a known reference, according to one aspect of the present invention. The method starts in step 1701 and then proceeds to step 1702 in which a reference beam pattern, such as that referred to as Data Set #1 above, is loaded from data store 1703 and converted from logarithmic values (for example dBi or dBm) into linear units of gain (unitless) or power (for example measured in milliwatts or Watts) if required ready for processing by the algorithm. The algorithm assumes than any values not included in the loaded data representing the reference beam pattern are set to a small linear value or a zero linear value, when performing its subsequent processing.

The method proceeds to step 1704 in which a beam pattern, referred to as Data Set #2 above, which has been measured in-situ using, for example, transmissions from a UE being received by a wireless device employing a beam-steering antenna system, is loaded from data store 1705 and converted from logarithmic values (for example dBi or dBm) into linear units of gain (unitless) or power (for example measured in milliwatts or Watts) if required ready for processing by the algorithm. The algorithm assumes than any values not included in the loaded data representing the measured beam pattern are set to a small linear value or a zero linear value, when performing its subsequent processing; this is discussed further below in relation to the shifted reference antenna pattern data. Note that whilst step 1704 has just been described in terms of loading a beam pattern from a data store, it could equally well refer to the measurement of that beam pattern, in real-time, using an in-situ wireless device, based upon, for example, transmissions from or reported by a UE. This newly-measured data is then available for processing by the algorithm.

The method then moves on to step 1706 in which the data corresponding to the reference beam pattern is shifted a number of steps to the left (based upon Figure 16(a), for example), i.e. its values are shifted in an angular sense negatively with respect to boresight such that the reference beam pattern and the measured beam pattern would have few or no valid points of overlap if they were plotted simultaneously on the same axes. The number of steps required to achieve this will depend upon the angular resolution with which the reference data set was measured or the desired number of steps to be used; for example it may be desirable to use a reduced version of the reference data set for the reference antenna pattern, taking for example every nth data point from the originally measured reference antenna pattern, where n is a positive integer greater than 1, in order to speed up the execution time of the algorithm. Taking the above example, discussed in relation to Figure 16, the reference data set, Data Set #1, had 100 points. If this data set is used unchanged, i.e. it is not reduced as just discussed, then the number of steps by which the reference data set would be required to be shifted would be approximately 100; whilst more than 100 steps could be used, the additional steps would typically produce no benefit to the algorithm nor the precision of its result. The shifted reference pattern data is stored in Data Store 1707 along with a sufficient number of small or zero values either side to ensure that the subsequent correlation processing does not yield erroneous results. In the example discussed in relation to Figure 16 above, at least 100 entries below the valid shifted reference pattern data and at least 100 entries above shifted reference pattern data would be required to be set to a small number or zero. To summarise, the result of the above processing yields two data sets with the following characteristics:

1. A reference antenna pattern data set containing approximately 3m storage locations, where the first m storage locations contain small or zero values of gain or signal strength, the second m storage locations contain linear values representing the reference antenna pattern typically in the form of gain or received signal power and the third m storage locations again contain small or zero values of gain or signal strength;

2. A measured antenna pattern data set, derived based upon the scanning or steering of a beam-steering antenna over a coverage area within which a UE, which it is desired to locate, is positioned, also contains approximately 3m storage locations. Here, again, the first m storage locations contain small or zero values of gain or signal strength, the second m storage locations contain linear values representing the measured antenna pattern typically in the form of gain or received signal power and the third m storage locations again contain small or zero values of gain or signal strength.

In step 1708 a counter value p is defined and set to zero.

In step 1709, a copy of the shifted reference pattern data is retrieved from Data Store 1707 along with its attendant low or zero values, as just discussed. This data is then shifted one location to the right, i.e. to a less negative angle with respect to boresight, and the resulting shifted reference pattern data is stored back into Data Store 1707. The counter is incremented by one (i.e. p now equals one).

In step 1710, each of the 3m data points of the measured antenna pattern data set is individually multiplied with a corresponding data point from the shifted reference pattern data set and the results of these multiple multiplications are summed together to form a single number. This correlation result value is stored in Correlation Store 1711, at location p, together with its corresponding beam angle, which is based upon the beam angle of the pt data point in the measured pattern data, where p is the value of the counter as noted above. Thus, for example, if the first data point in the original measured pattern data was taken at a beam angle of -45 degrees with respect to boresight, then the beam angle which would be stored along with this first correlation result value would be -45 degrees.

In this first iteration of the method, there is only one data point which will overlap between the two data sets, which is that of the upper end of the original reference pattern data set and the lower end of the original measured pattern data set, with all other points being, for example, zero, in one or other of the data sets.

In step 1712, the counter value p is compared to double the pattern length of the original reference pattern data set (prior to adding any low or zero values), i.e. 2m; if p is greater than or equal to 2m then the method moves on to step 1713, otherwise it returns to step 1709 and the section from 1709 to 1712 repeats.

At step 1713, the beam angle corresponding to the highest correlation result value stored in the Correlation Store 1711 is reported as a likely angular position or bearing of the UE relative to a boresight direction of the antenna array. The method then ends at step 1714. Note that in step 1709 it is possible to shift the reference pattern data by a step size of greater than one, for example a step size of 10, in order to increase the speed of execution of the algorithm. The resulting estimate for an angular separation between boresight and a location of the UE may be poorer as a result of the larger step size, however it may be sufficient to provide an approximate location. The algorithm could then be run again, but utilising a restricted range of search angles, based upon the approximate angle derived in the first pass of the algorithm and an estimated error bound (for example +/- 5 steps or +/- 5 degrees) and a smaller step size, such as a step size of one, could then be used to more accurately locate the UE.

Likewise, the number of data points stored for the reference antenna pattern and the measured antenna pattern need not be the same. It may, for example, be advantageous to take fewer measurement points in order to form the measured antenna pattern, since the time taken to undertake these measurements will directly impact upon the time taken to provide an estimate of the location of a UE. In the case of a reduced number of data points being used, the method could either utilise a step size commensurate with the lower number of data points, for example using a step size of 10 in the case where the measured antenna pattern contains 1/10* of the number of data points as the measured antenna pattern, or the step size could remain at 1 , with all positions then being correlated, as previously, and some values yielding a null or neutral result.

Figure 18 shows an analogous situation to that of Figure 16, with Figure 18(a) being analogous to (and indeed identical to) Figure 16(a), Figure 18(b) being analogous to Figure 16(b) and Figure 18(c) being analogous to Figure 16(c). The general situation illustrated is the same in both cases, being that of an antenna reference radiation pattern (Figure 18(a)), a measured antenna radiation pattern based upon signals from a UE located approximately 20 degrees to the right of boresight (Figure 18 (b)) and a correlation characteristic resulting from correlating these two radiation patterns in the manner described above with reference to Figure 16 and Figure 17. The key difference between Figure 18 and Figure 16 is that Figure 18(b) has been derived using 10 degree angular steps based upon measurements of a UE signal strength received at a steerable antenna array when steered in 10 degree steps, whereas Figure 16(b) utilised 1 degree steps. Considering now the two correlation results, Figure 18(c) and Figure 16(c), it is clear that there is very little difference between them; both exhibit a clear peak at an offset from boresight of +20 degrees and both also exhibit a relatively sharp and well-defined peak, despite the very coarse angular resolution utilised in deriving Figure 18(b). This figure clearly shows, therefore, that a relatively coarse angular step size may be employed, when sweeping a steerable antenna beam across an area in an attempt to locate a UE, with the resulting angular location estimate obtained when using a relatively coarse step size of 10 degrees being virtually indistinguishable from that obtained using a much finer step size of 1 degree. Thus a total number of angular measurement steps of under 20 can yield a similar angular location accuracy to that of approximately 180 steps or more, in this example. The above-discussed step sizes, angular resolutions and offset values are examples which illustrate the power of the correlation technique and should in no way be taken as limiting or even optimum values for any or all of these parameters.

The above discussion was based upon the angular location of a UE by a single steerable antenna array; clearly this will result in a quasi-linear locus of possible UE locations, for the reasons discussed above in relation to Figure 5 to Figure 10. The same or a similar correlation processing just described may also be applied to a second, independent, orthogonal steerable antenna array and a second, orthogonal, angular location of a UE may be obtained, typically simultaneously with the first. Again this second angular location will result in a quasi-linear locus of possible UE locations, when considered in isolation. If, however the two loci, one obtained from a first steerable antenna array and another from a second, orthogonal (or at least non- parallel), steerable antenna array, are intersected, then a point of intersection can typically provide a single, accurate, location for a UE.

Once a UE has been initially located, or if some a priori information is available to narrow down the range of possible locations for the UE, it is possible to apply the above correlation-based technique, or any other correlation or other UE search technique such as those further described below, over a narrower angular field of search. This could, for example, form the basis of a following or continuous tracking mechanism for the UE, whist taking far fewer processing resources and requiring far fewer signal strength measurements and hence data packets upon which to base signal strength measurements, in the case of a packetized radio system such as Wi-Fi. This, in turn, may make the location technique quicker and more responsive.

The above discussion has concentrated upon the use of a correlation technique based upon the use of the antenna main lobe; it is equally possible to base the technique upon one or more side-lobes or upon nulls in the antenna characteristic or any other combination of antenna radiation pattern characteristic features which can be matched between a reference antenna characteristic and a deployed-system antenna characteristic.

Figure 3 (discussed above) showed a number of conventional options for an antenna array of a form suitable for use with a geolocation technique of the form described above. The array configuration options shown in Figure 3 have the disadvantage that they are relatively large and therefore would result in a relatively large overall product size, for a geolocation product utilising the architectures and techniques described thus far, notably when used in a lower frequency band, such as the 2.45GHz frequency band. Figure 19 shows an improved antenna array design 1900 which is also suitable for use in a geolocation system such as that described above, but which occupies a reduced area and hence can result in a reduced product size, a reduced size for a printed circuit board (PCB) upon which or above which antenna elements may be fabricated or mounted or both and consequently a reduced product cost and a greater likely acceptability of a product in the marketplace. In the example shown in Figure 19, four fewer elements are required than in an equivalent implementation shown in Figure 3(a) if a 4x4 MIMO scenario is considered thereby meaning that all 16 elements shown in Figure 3(a) were being used. Furthermore, the board area required can reduce to under half of that required with the original design shown in Figure 3(a).

The essential difference between the antenna array shown in Figure 19 and that shown in Figure 3(a) is that 'corner' elements are shared between horizontally-oriented sub- arrays and vertically-oriented sub-arrays in the arrangement shown in Figure 19. The sharing of these elements is made possible by utilising different polarisations for two orthogonal sub-arrays, with a corner element common to the orthogonal sub-arrays being dual-polarised, operating on one polarisation with a horizontally-oriented sub- array, say, and an orthogonal polarisation with a vertically-oriented sub-array, as will now be described with reference to Figure 20.

Figure 20 shows an antenna array 2000 consisting of three independent antenna sub- arrays incorporating a number of elements which are shared between some of the sub- arrays. The arrangement shown in Figure 20 would typically be utilised to form three sub-arrays, for example to transmit and receive signals from a 3x3 MIMO configured wireless access point, although other configurations are possible with the same, or a similar arrangement of antenna elements. In one embodiment, Figure 20 may for example consist of a first sub-array, consisting of antenna elements 2001a, 2001b, 2001c, 200 Id, a second sub-array, consisting of antenna elements 2001a, 2002b, 2002c, 2002d and a third sub-array, consisting of antenna elements 2001d, 2003b, 2003c, 2003d. In this arrangement, antenna element 2001a is shared between the first sub-array and the second sub-array and antenna element 200 Id is shared between the first sub-array and the third sub-array. Antenna element 2001a is configured as a dual-polar antenna element as is evidenced by the two feed-points 2011a and 2012a shown in Figure 20; further details of example antenna configurations for dual-polar antenna elements will be discussed below with reference to Figure 26, Figure 27 and Figure 28. Antenna element 200 Id is also configured as a dual-polar antenna element as is evidenced by the two feed-points 201 Id and 2013a shown in Figure 20.

Feed-points 201 la, 201 lb, 201 lc, 201 Id are all located at a similar position in relation to their respective antenna elements 2001a, 2001b, 2001c, 200 Id, in a roughly upper- central location. These feed-points will typically, therefore, excite a similar polarisation to each other and a sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id is therefore capable of operating as a steerable-beam array when connected to a suitable beamformer and ancillary circuits, as described previously.

Feed-points 2012a, 2012b, 2012c, 2012d are also all located at a similar position in relation to their respective antenna elements 2001a, 2002b, 2002c, 2002d, in this instance in a roughly left-hand central location. These feed-points may also, typically, excite a similar polarisation to each other and a sub-array formed from antenna elements 2001a, 2002b, 2002c, 2002d is therefore also capable of operating as a steerable-beam array when connected to a suitable beamformer and ancillary circuits, as described previously. A sub-array formed from antenna elements 2001a, 2002b, 2002c, 2002d may impose an approximately orthogonal polarisation on signals radiated or received by that sub-array relative to a sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id, due to the relative difference in the position of feed-points, relative to their respective antenna elements, between the two sub-arrays.

A steerable sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id may operate independently of a steerable sub-array formed from antenna elements 2001a, 2002b, 2002c, 2002d, for example when each sub-array is fed with independent channels or signals from a MIMO transceiver, despite the fact that antenna element 2001a is shared and is common to both sub-arrays. The independence of these two sub-arrays, despite their sharing of antenna element 2001a, arises from the minimal interaction which typically takes place between orthogonal polarisations radiated or received by a dual-polarisation antenna element or sub-array. Each sub-array can therefore operate largely as if it had exclusive use of shared antenna element 2001a. Likewise, with a sub-array formed from antenna elements 200 Id, 2003b, 2003c, 2003d, and its shared use of antenna element 200 Id with a sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id. In this case, feed-points 2013a, 2013b, 2013c, 2013d are arranged in a roughly right-hand central location. These feed-points may also, typically, excite a similar polarisation to each other and a sub- array formed from antenna elements 2001d, 2003b, 2003c, 2003d is therefore also capable of operating as a steerable-beam array when connected to a suitable beamformer and ancillary circuits, as described previously. A sub-array formed from antenna elements 2001d, 2003b, 2003c, 2003d may impose an approximately orthogonal polarisation on signals radiated or received by that sub-array relative to a sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id, due to the relative difference in the position of feed-points, relative to their respective antenna elements, between the two sub-arrays. The spatial separation between a sub-array formed from antenna elements 2001a, 2001b, 2001c, 200 Id and a sub-array formed from antenna elements 2001d, 2003b, 2003c, 2003d will typically ensure that they operate independently of one another, despite both sharing a similar polarisation orientation, albeit potentially in inverse phase, in some implementations. In a typical scenario, for example when connected to a 3x3 MIMO transceiver, each sub-array would typically radiate different channels or signals hence providing a further degree of independence between the sub-arrays.

Figure 21 illustrates a variant of the arrangement shown in Figure 20, in this instance four sub-arrays may be formed providing antenna array 2100 with a capability to radiate four independent channels or signals, for example when used in conjunction with a 4x4 MIMO transceiver. As an example, four sub-arrays which may be formed from the antenna elements illustrated in Figure 21 are:

Sub-array #1 consisting of antenna elements 2101a, 2101b, 2101c, 2101d and feed-points 2111.

Sub-array #2 consisting of antenna elements 2101a, 2102b, 2102c, 2102d and feed-points 2112. Sub-array #3 consisting of antenna elements 21 Old, 2103b, 2103c, 2103d and feed-points 2113.

Sub-array #4 consisting of antenna elements 2102d, 2104b, 2104c, 2103d and feed-points 2114. Sub-array #1 and sub-array #2 share antenna element 2101a; sub-array #2 and sub- array #3 share antenna element 21 Old; sub-array #3 and sub-array #4 share antenna element 2103d; sub-array #2 and sub-array #4 share antenna element 2102d.

In the example configuration shown in Figure 21, with the feed-point locations shown in that figure, Sub-array #1 and sub-array #2 will typically exhibit approximately orthogonal polarisations to each other. Likewise, sub-array #1 and sub-array #3 will typically exhibit approximately orthogonal polarisations to each other, sub-array #3 and sub-array #4 will typically exhibit approximately orthogonal polarisations to each other and sub-array #2 and sub-array #4 will also typically exhibit approximately orthogonal polarisations to each other. Operation of the antenna array 2100 shown in Figure 21 is analogous to that of antenna array 2000 shown in Figure 20, with the exception that a fourth sub-array (sub-array #4) has been added in Figure 21, and hence it will not be described further, here.

Figure 22 shows an alternative configuration for the antenna elements shown in Figure 21. Again, four sub-arrays may be formed from this arrangement, for example:

Sub-array #la consisting of antenna elements 2201a, 2201b, 2201c, 2201d and associated upper-most feedpoints of these antenna elements.

Sub-array #2a consisting of antenna elements 2201b, 2202b, 2202c, 2204b and associated left-most feed-points of these antenna elements. Sub-array #3a consisting of antenna elements 2201c, 2203b, 2203c, 2204c and associated right-most feed-points of these antenna elements. Sub-array #4a consisting of antenna elements 2204a, 2204b, 2204c, 2204d and associated lower-most feed-points of these antenna elements.

Note that many other variants of this configuration are possible, such as swapping the first and second or third and fourth columns of antenna elements or flipping (mirroring) the second column of elements from left-to-right about its centreline and/or flipping (mirroring) the third column of elements from left-to-right about its centreline. Finally, flipping (mirroring) each of the first and/or fourth rows of elements from top-to-bottom about its own centreline is a further, potentially valid, variant. Figure 23 illustrates a variant of Figure 21 in which the first and fourth columns of antenna elements in that figure have been flipped or mirrored from left-to-right about their respective centrelines. The operation of the resulting antenna array 2300 is analogous to that described in relation to Figure 21.

Figure 24 illustrates a still further variant of Figure 21 in which the first and fourth columns of antenna elements in that figure have been flipped or mirrored from left-to- right about their respective centrelines and the first and fourth rows of antenna elements have been flipped or mirrored from top-to-bottom about their respective centrelines. The operation of the resulting antenna array 2400 is analogous to that described in relation to Figure 21. Figure 25 illustrates a simpler example antenna array 2500 consisting of two sub- arrays, one oriented horizontally and a second oriented vertically, which intersect partway along each (the prior examples showed arrays intersecting at an extreme end of one or other or both of at least one sub-array). Sub-array A may consist of antenna elements 2501a, 2501b, 2501c, 250 Id, and sub-array B may consist of antenna elements 2502a, 2501b, 2502c, 2502d, with sub-array A and sub-array B typically exhibiting approximately orthogonal polarisations to each other. Antenna array 2500 is suitable for radiating or receiving typically two separate signals, and as such it would be suitable for use with a 2x2 MIMO transceiver, for example. The operation of the resulting antenna array 2500 is analogous to that described in relation to Figure 21, albeit with only two sub-arrays in place of the three illustrated in that figure. 1.In some, or all, of the above-described antenna array configurations, the antenna array may utilise a separation distance between the centre points of any two of the sub-arrays, of at least one-half wavelength defined at the centre frequency of the intended operating bandwidth of the array. Such a separation distance may be necessary to ensure that each sub-array may be considered independent of some or all of the other sub-arrays and MIMO signals transmitted or received by the sub-arrays may be considered to be largely statistically independent of one another.

2. The antenna array may comprise antenna elements arranged to radiate or receive linearly polarised signals in which a vertically-polarised signal, say, is considered to be orthogonal to a horizontally-polarised signal. Equally, the antenna array may comprise antenna elements arranged to radiate or receive circularly polarised signals in which a right-hand circular polarisation is considered to be orthogonal to a left-hand circular polarisation. Whilst the antenna element embodiments to be described below are configured as dual- polar or bipolar, linearly-polarised elements, variants of each are known in the art which are capable of generating circularly polarised signals and these examples of linearly polarised antenna elements should not be taken as limiting examples. Likewise, the single-polar antenna elements discussed above may be implemented as either linearly polarised elements or circularly polarised elements, as is known in the art.

3. Whilst Figure 20 to Figure 25 illustrate antenna sub-arrays which are oriented orthogonally to one another, it is not essential to the essence invention that they are so oriented, so long as they are designed appropriately and are non- parallel. For example, the orientation of the primary axis of the first sub-array may subtend an angle of greater than 5 degrees and less than 175 degrees to the orientation of the primary axis of the second sub-array.

Figure 26 illustrates one embodiment of a dual-polarisation or bipolar patch antenna element 2600 showing both a top-view (Figure 26(a)) and a side view of a laminate structure from which such an element may be constructed (Figure 26(b)). Considering, firstly, Figure 26(a), an approximately square patch antenna element 2601 is supplied with independent RF signals within its resonant capability via transmission lines 2603 (for a first independent signal) and 2604 (for a second independent signal). A signal entering antenna radiating element 2601 via transmission line 2603 will excite antenna element 2601 largely in a first polarisation orientation; a second signal entering antenna radiating element 2601 via transmission line 2604 will excite antenna radiating element 2601 largely in a second polarisation orientation wherein the second polarisation orientation is substantially orthogonal to the first polarisation orientation. Both polarisations can co-exist within the single antenna radiating element 2601 and may conduct within the structure and radiate from the structure largely independently of one another.

Figure 26(b) shows an example laminar structure from which patch antenna element 2600 may be constructed. Upper conducting layer 2602 is patterned with a structure of the form shown in Figure 26(a) such that the aspects of Figure 26(a) which appear within the outline, for example antenna radiating element 2601 and the transmission lines 2603 and 2604 are formed from a conducting material, such as copper, and surrounding conducting material has been removed. Upper conducting layer 2602 is located upon a dielectric layer 2608 which separates it from a conducting ground- plane layer 2609; dielectric layer 2608 may consist of air, foam, FR4, PTFE (Polytetrafluoroethylene) or any other suitable dielectric material.

Figure 27 illustrates a second embodiment of a dual-polarisation or bipolar patch antenna structure 2700 showing both a top-view (Figure 27(a)) and a side view of a laminate structure from which such an element may be constructed (Figure 27(b)).

Considering, firstly, Figure 27(a), an approximately square patch antenna radiating element 2701 is supplied with independent RF signals within its resonant capability via transmission lines 2703 (for a first independent signal) and 2704 (for a second independent signal) utilising feed-probes 2705 and 2706 respectively. A first signal entering antenna radiating element 2701 via transmission line 2703 and feed-probe 2707 will excite antenna radiating element 2701 largely in a first polarisation orientation; a second signal entering antenna radiating element 2701 via transmission line 2704 and feed-probe 2706 will excite antenna radiating element 2701 largely in a second polarisation orientation wherein the first polarisation orientation is typically substantially orthogonal to the second polarisation orientation. Both polarisations can co-exist within single antenna radiating element 2701 and may conduct within the structure and radiate from the structure largely independently of one another. Figure 27(b) shows an example laminar arrangement from which patch antenna structure 2700 may be constructed. Upper conducting layer 2702 is patterned with a structure of a form shown as patch antenna radiating element 2701 in Figure 27(a) such that the aspects of patch antenna radiating element 2701 which appear within the outline are formed from a conducting material, such as copper, and surrounding conducting material has been removed. Upper conducting layer 2702 is located upon a dielectric layer 2707 which separates it from a conducting ground-plane layer 2710 within which apertures are formed by the local removal of conducting material forming the ground-plane layer 2710. Through these apertures, feed-probes 2711 (analogous to feed-probe 2705 of Figure 27(a)) and 2712 (analogous to feed-probe 2706 of Figure 27(a)) pass, from a further conducting layer onto which transmission lines 2703 and 2704 are patterned. This further conducting layer is separated from ground-plane layer 2710 by a second dielectric layer 2708 (which may utilise a different dielectric material to dielectric layer 2707).

Dielectric layers 2707 and 2708 may consist of one or more of: air, foam, FR4, PTFE (Polytetrafluoroethylene) or any other suitable dielectric material.

Returning to Figure 27(a), a first radio-frequency signal may enter dual-polarisation patch antenna structure 2700 via transmission line 2703. It may pass along this line until it reaches feed-probe 2705 which conducts the signal from the lower conducting layer 2709 to the upper conducting layer 2702 of Figure 27(b), passing through an aperture in the ground-plane layer 2708 of Figure 27(b), whereupon it may initiate or sustain a resonance in patch antenna radiating element 2701 of Figure 27(a) and consequently radiate a first radio-frequency signal. Likewise, a second radio- frequency signal may enter dual-polarisation patch antenna structure 2700 via transmission line 2704. It may pass along this line until it reaches feed-probe 2706 which conducts the signal from the lower conducting layer 2709 to the upper conducting layer 2702 of Figure 27(b), passing through an aperture in the ground- plane layer 2708 of Figure 27(b), whereupon it may initiate or sustain an approximately orthogonal resonance to that of the first signal in patch antenna radiating element 2701 of Figure 27(a) and consequently radiate this second signal.

Figure 28 illustrates a third embodiment of a dual-polarisation or bipolar patch antenna structure 2800 showing both a top-view (Figure 28(a)) and a side view of a laminate structure from which such an element may be constructed (Figure 28 (b)).

Considering, firstly, Figure 28(a), an approximately square patch antenna radiating element 2801 is supplied with independent RF signals within its resonant capability via transmission lines 2803 (for a first independent signal) and 2804 (for a second independent signal) utilising apertures 2805 and 2806 respectively. A first signal to be radiated enters via transmission line 2803 and is coupled to patch antenna radiating element 2801 via aperture 2805 largely in a first polarisation orientation; a second signal to be radiated enters via transmission line 2804 and is coupled to antenna element 2801 via aperture 2806 largely in a second polarisation orientation wherein the a second polarisation orientation is substantially orthogonal to the a first polarisation orientation. Both polarisations can co-exists within single patch antenna radiating element 2801 and may conduct within the structure and radiate from the structure largely independently of one another.

Figure 28(b) shows an example laminar arrangement from which patch antenna structure 2800 may be constructed. Upper conducting layer 2802 is patterned with a structure of a form shown as patch antenna radiating element 2801 in Figure 28(a) such that the aspects of patch antenna radiating element 2801 which appear within the outline are formed from a conducting material, such as copper, and any surrounding conducting material has been removed. Upper conducting layer 2802 is located upon a dielectric layer 2807 which separates it from a conducting ground-plane layer 2810 within which apertures (2805 and 2806 of Figure 28(a)) are formed by the local removal of the conducting material forming the ground-plane. Partially underneath these apertures transmission lines (2803 and 2804 of Figure 28(a)) are patterned within conducting layer 2809. This further conducting layer is separated from ground-plane layer 2810 by a second dielectric layer 2808 (which may utilise a different dielectric material to dielectric layer 2807). Dielectric layers 2807 and 2808 may consist of one or more of: air, foam, FR4, PTFE (Polytetrafluoroethylene) or any other suitable dielectric material.

Returning to Figure 28(a), a first radio-frequency signal may enter dual-polarisation patch antenna structure 2800 via transmission line 2803. It may pass along this line until it reaches aperture 2805 which allows the electromagnetic field formed above the transmission line to couple to patch antenna radiating element 2801 whereupon it may initiate or sustain a resonance in patch antenna radiating element 2801 and consequently radiate a first radio-frequency signal. Likewise, a second radio- frequency signal may enter dual-polarisation patch antenna structure 2700 via transmission line 2804. It may pass along this line until it reaches aperture 2806 which allows the electromagnetic field formed above the transmission line to couple to patch antenna radiating element 2801 whereupon it may initiate or sustain an approximately orthogonal resonance to that of the first signal in patch antenna radiating element 2801 and consequently radiate this second signal. While the features and functionalities for estimating a spatial location of one or more fixed or mobile transmitting and/or receiving devices are primarily discussed with respect to the embodiments above, it should be appreciated that the features and functionalities of one embodiment may be similarly applied to other embodiments. Furthermore, although the embodiments described above do not require use of GPS technology, it may be readily appreciated that the features and functionalities described herein may be used in conjunction with such technologies as well.

In the preceding specification, various embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the disclosure as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.

At this point it should be noted that estimating a spatial location of one or more fixed or mobile transmitting and/or receiving devices in accordance with the present disclosure as described above typically involves the processing of input data and the generation of output data to some extent. This input data processing and output data generation may be implemented in hardware or software. For example, specific electronic components may be employed in a spatial location module or similar or related circuitry for implementing the functions associated with estimating a spatial location of one or more fixed or mobile transmitting and/or receiving devices in accordance with embodiments described above. Alternatively, one or more processors operating in accordance with instructions may implement the functions associated with estimating a spatial location of one or more fixed or mobile transmitting and/or receiving devices in accordance with embodiments as described above. If such is the case, it is within the scope of the present disclosure that such instructions may be stored on one or more processor readable storage media (e.g., a magnetic or optical disk or other storage medium), or transmitted to one or more processors via one or more signals embodied in one or more carrier waves.

In the above discussion, the term 'processors' includes any digital or analogue device which is capable of processing signals or data and includes, but is not limited to, microprocessors, Peripheral Interface Controller ("PIC") processors, complex programmable logic devices (CPLDs), Application-Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs) and all similar or related devices.

The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein. Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art are considered to fall within the spirit and scope of the invention broadly appearing before described.