The present disclosure relates to antenna array apparatus, for example to an antenna array apparatus including a phased array of transmitters and/or receivers, for example operating at electromagnetic radiation frequencies in an order of 77 GHz. Moreover, the present disclosure concerns methods of operating aforementioned antenna array apparatus. Furthermore, the present disclosure is concerned with computer program products comprising a non- transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute aforesaid methods. Background

Antenna array arrangements are well known, for example a two-dimensional, or even three-dimensional, antenna array arrangement including a plurality of emitting and/or receiving elements enables a preferred polar distribution of overall emission and/or reception to be achieved; the elements are often referred as being "apertures" , "sub-elements" or "sub-apertures" . The elements are excited by a common signal, which is relatively adjusted in phase and/or amplitude in respect of the elements to achieve a desired polar characteristic of emission. Likewise, signals received at the elements are amplified and adjusted in relative phase and/or amplitude to achieve a desired polar characteristic of reception. Optionally, the adjustments in phase and/or amplitude are fixed, in which case the antenna array arrangement provides a fixed polar characteristic of emission and/or reception. Alternatively, optionally, the adjustments in phase and/or amplitude are made temporally dynamically changeable, as in agile steerable radar systems. Agile steerable radar systems are contemporarily employed in civil aviation, in coastal surveillance and in military systems. The antenna array arrangements optionally have their elements arranged in a regular spatial formation, for example in a rectilinear format, or in an irregular format, for example wherein the elements are disposed in a curved surface, for example a fuselage of an aircraft or vehicle. In operation, selecting suitable phase and/or amplitude adjustments to be used for the plurality of elements of a given antenna array arrangement is not a trivial task, but is achievable, for example, by using computer control with reference to one or more look-up tables or algorithms that relate polar characteristics to corresponding phase and/or amplitude adjustments for the elements. Optimization of the phase and/or amplitude adjustments under real operating conditions, in which there are both desired sources of radiation being monitored by the given antenna array arrangement as well as unwanted interfering sources within a same polar region as the desired sources of radiation, is a complex technical problem which has been the subject matter of considerable research and earlier inventions reported in the prior art. In contemporary practice, when a given antenna array apparatus has been initially manufactured, it is thereafter subject to a calibration process to adjust its parameters to achieve a desired polar performance and/or a characterizing process for measuring its achieved polar performance.

In a United States patent US 7, 969, 349 B2 (inventor: Timothy R. Holzheimer et al., applicant: Raytheon Company, USA), there is described a system for processing electromagnetic waves in a radar system; the radar system is, for example, mounted upon a road vehicle when in operation. The system includes a transmitter that is operable to transmit operating waves and calibration waves. Moreover, the system includes one or more receivers that are operable to receive reflected calibration waves and operating waves. Furthermore, the system includes a system controller that is operable to process the received calibration waves and operating waves. Optionally, the system controller processes the received waves by generating a threshold signal based upon the calibration waves, and comparing the threshold signal to the operating waves. Moreover, optionally, the system controller also processes the operating waves and the calibration waves in accordance with one or more signal conditioning algorithms. Furthermore, optionally, the system controller displays an image representing a target on a display by comparing received operating waves with the generated threshold signal.

In a United States patent application US 2005/0128136 A1 , "System and method for Radar Detection and Calibration" (inventors: Peter S. Wittenberg and John Hayn), there is described a system for performing radar detection and calibration, and a method of operating the system. By measuring a true range of a calibration target on entry to a radar system's detection zone, an actual detection capability of the radar system in given atmospheric conditions is determined. The radar system is also described as being operable to determine a sensed position at a sensed time of a target in the radar system's detection zone. A calibration target, for example an unmanned air vehicle (UAV), includes a position device for determining an actual spatial position of the calibration target. A calibration device communicates with the radar system and the calibration target and receives the sensed and actual positions of the calibration target. The calibration device calculates an error between the sensed position and the actual position and adjusts the radar system to reduce, for example to minimize, the error. The target optionally includes a signal augmentation device to augment an associated radar cross-section of the target to replicate radar cross-sections of targets of various types. In such a manner, a true detection range of the radar system is determined for various types of targets under the given current atmospheric conditions.

In a WIPO patent application WO 2005/025963 A1 , "A Monitoring Device" (inventors: Borje Eklund and Hans Undin), there is described a device for monitoring an area to detect, whether or not an undesired object is present within the area; there is also described a method of operating the device. The device includes a laser for emitting a laser beam of a determined wavelength over the area and a photosensor for receiving a reflected part of the laser beam and generating a signal depending upon the reflected part of the laser beam. The device further includes an evaluation unit for processing the generated signal to determine whether or not an undesired object is present within the area. The laser is operable to emit a laser beam having a wavelength that is longer than, or equal to, 1200 nm .

In a United States patent application US 2009/0201489 A1 , "Monitoring Device" (inventors: Borje Eklund, Hans Undin and Orjan Altebro; assignee: Avalon Innovation AB), there is described a device for monitoring a delimited area to detect whether or not an undesired object is present within the area; there is also described a method of operating the device. The device includes a laser for emitting a laser pulse of a determined wavelength over the area and a first photosensor for receiving a reflected part of the laser pulse. The device further includes an evaluation unit for measuring the reflected part of the laser pulse during a predetermined time period after the laser pulse has been emitted from the laser to generate a signal depending on the measured reflected part, and for processing the generated signal to determine whether or not an undesired object is present within the area.

In a WIPO application WO 2001/053851 A1 , "Method and Arrangement for Detecting Objects" (inventors: Daniel Lehnberg and Bert-Eric Tullsson, applicant: Saabtech Electronics AB), there is described an arrangement for detecting objects in a track area of an underground railway station, via a radar sensor mounted in a fixed manner relative to the track area; there is also described a method of operating the arrangement. Information supplied by the radar sensor is processed for detecting new stationary objects and/or moving objects. A surveillance area of the radar sensor is limited along parts of the track area by excluding combinations of distance and angle that are not to be included in the surveillance area. The surveillance area is operable to be deployed on tunnel walls of the underground station.

In an example contemporary radar system having an antenna array arrangement for emitting and/or receiving electromagnetic radiation, sub-aperture partitioning into several smaller apertures that are larger than one wavelength is a common approach. Such an antenna array arrangement is operable to have ambiguous directions of polar sensitivity. One way to suppress such ambiguous directions of polar sensitivity is to employ staggered sub-apertures, or irregularly distributed phase centres for the apertures. However, such irregular distributed apertures do not automatically suppress ambiguities for every direction of arrival (DOA). Referring to FIG. 1, there is shown a spatial disposition of elements of an antenna array arrangement, wherein the elements, referred to also as "apertures" , are denoted by circles and identified by reference codes RXantl to RXant9. The elements RXantl to RXant5 are disposed in a first linear arrangement in a first direction, and the elements RXantl together with the elements RXant6 to RXant9 are disposed in a second linear arrangement in a second direction; the first and second directions are mutually orthogonal, as shown. Spacings, namely "pitches" between the elements, are denoted by D1 to D8 in FIG. 1; for example, a pitch D2 defines a spacing between the elements RXant2 and RXant3. However, in an oblique direction, relative to the first and second directions, there are ambiguous directions given by a smallest pitch between vertical elements in the second direction, namely the elements Rxant 6 to 9, and horizontal elements in the first direction, namely the elements Rxant 1 to 5. In FIG. 1, an example of an ambiguous direction is denoted by a dotted arrow between the elements RXant2 and RXant6.

With each element RX is associated a corresponding phase centre, when the antenna array arrangement is in operation. As illustrated, the phase centres are potentially irregular, either by intentional design or by tolerances in manufacture. When the antenna array arrangement is intended for operation at high radar frequencies, for example as employed in millimetric radar systems functioning at electromagnetic radiation frequencies in an order of 77 GHz, tolerances potentially arise in normal manufacturing processes when constructing the antenna array arrangement. Thus, a randomly-made irregular distribution of the phase centres of the elements RX will not suppress all ambiguous directions for any direction of arrival (DOA), when the antenna array arrangement is in operation as a part of a radar system. In order to assess an adequate antenna layout, there arises a need to analyse ambiguous DOA characteristics of the antenna array arrangement for all potential DOA's. Such analysis, and also corresponding correction thereof, needs to be balanced with other key performance criteria, such as accuracy and resolution capability of the antenna array arrangement when used as a part of a radar system.

A technical problem arises to find an irregular phase centre distribution for the elements RX in FIG. 1 that is operable to suppress all ambiguous polar directions of the array of elements RX, namely merely only along the aforementioned first and second directions. A largest distance or pitch between the phase centres along an oblique direction determines an ability of the array of element RX to suppress ambiguous directions along the oblique direction. Such ambiguous directions result in the array of elements RX, with its associated signal processing apparatus, not being able to be used to determine, for example, whether or not an obstacle reflecting broad-beam radiation from a transmitter (TX) is on a left-hand-side or a right-hand-side along that oblique direction. For some example fields of use of the antenna array arrangement, for example in automotive radar-assisted steering and/or radar assisted braking, such ambiguity potentially has serious safety implications in use.

Aforementioned ambiguities in directions of polar sensitivity of the antenna array arrangement, as generally types of antenna array arrangements, represents a technical problem that the present disclosure seeks to address.

Summary

The present disclosure seeks to provide an improved antenna array apparatus that is operable to exhibit reduced ambiguities in its polar sensing and/or emission characteristics.

Moreover, the present disclosure seeks to provide an improved method of operating an antenna array apparatus to exhibit reduced ambiguities in its polar sensing and/or emission characteristics.

According to a first aspect, there is provided an antenna array apparatus including an antenna array arrangement that is operable with a data processing arrangement to emit electromagnetic radiation from the antenna array arrangement and/or to receive electromagnetic radiation at the antenna array arrangement, characterized in that the antenna array arrangement includes a plurality of elements disposed in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag manner in respect of a second direction relative to an elongate first direction of the rows.

The present invention is of advantage in that the zig-zag disposition of the phase centres is capable of resulting in the polar characteristics of the antenna array arrangement including less ambiguous polar sensing directions when receiving and/or emitting electromagnetic radiation. By "zig-zag manner", there is denoted an alternating spatial and/or angular manner; for example, a "w" letter shape is an example of a zig-zag wherein two linear portions of the "w" letter are mutually parallel in a first direction, two linear portions of the "w" letter are mutually parallel in a second direction, and wherein the portions of the first and second directions are disposed alternately in series; joining points of the linear portions are disposed in an alternating zig-zag manner. However, it will be appreciated that a zigzag manner can include two or more alternations, for example three alternations, four alternations and so forth. Optionally, in the antenna array apparatus, the plurality of phase centres are spatially disposed in a W-shape manner along the second direction.

Optionally, in the antenna array apparatus, the plurality of phase centres are spatially disposed in a symmetrical manner along the second direction.

Optionally, in the antenna array apparatus, the second direction is substantially orthogonal to the first direction. By "substantially orthogonaF is meant in a range of 70° to 110° relative angle between the first and second directions, more optionally in a range of 85° to 95° relative angle between the first and second directions.

Optionally, in the antenna array apparatus, at least a portion of the plurality of elements is spatially disposed in a planar manner. For example, the plurality of elements is fabricated via use of a planar substrate printed circuit board.

Optionally, in the antenna array apparatus, at least a portion of the plurality of elements is spatially disposed in a curved surface. More optionally, in the antenna array apparatus, the curved surface is curved in 1 -dimension. More optionally, in the antenna array apparatus, the curved surface is curved in 2- dimensions.

Optionally, in the antenna array apparatus, the rows of elements are disposed at irregular spatial distances along the second direction. Alternatively, optionally, in the antenna array apparatus, the rows of elements are disposed at regular spatial distances along the second direction. Optionally, in the antenna array apparatus, the elements are disposed at regular spatial distances along their respective rows. Alternatively, optionally, in the antenna array apparatus, the elements are disposed at irregular spatial distances along their respective rows.

Optionally, in antenna array apparatus, the antenna array arrangement is operable to emit and/or to receive electromagnetic radiation having principal signal components that lie in a range of 40 GHz to 200 GHz. More optionally, in the antenna array apparatus, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 50 GHz to 100 GHz. Yet more optionally, in the antenna array apparatus, the antenna array arrangement is operable to emit and/or to receive electromagnetic radiation having principal signal components of substantially 77 GHz.

According to a second aspect, there is provided a method of operating an antenna array apparatus including an antenna array arrangement that is operable with a data processing arrangement to emit electromagnetic radiation from the antenna array arrangement and/or receive electromagnetic radiation at the antenna array arrangement, characterized in that the method includes:

disposing a plurality of elements of the antenna array arrangement in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag manner in respect of a second direction relative to an elongate first direction of the rows.

Optionally, the method includes spatially disposing the plurality of phase centres in a W-shape manner along the second direction. Optionally, the method includes spatially disposing the plurality of phase centres in a symmetrical manner along the second direction.

Optionally, in the method, the second direction is substantially orthogonal to the first direction. By "substantially orthogonaf is meant in a range of 70° to 110° relative angle between the first and second directions, more optionally in a range 85° to 95° relative angle between the first and second directions.

Optionally, the method includes spatially disposing at least a portion of the plurality of elements in a planar manner. For example, the plurality of elements is fabricated via use of a planar substrate printed circuit board.

Optionally, the method includes spatially disposing at least a portion of the plurality of elements in a curved surface. More optionally, in the method, the curved surface is curved in 1-dimension. More optionally, in the method, the curved surface is curved in 2-dimensions.

Optionally, in the method, the rows of elements are disposed at irregular spatial distances along the second direction.

Optionally, in the method, the elements are disposed at regular spatial distances along their respective rows.

Optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 40 GHz to 200 GHz. More optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 50 GHz to 100 GHz. Yet more optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components of substantially 77 GHz.

According to a third aspect, there is provided a computer program product comprising a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute a method pursuant to the second aspect.

According to a fourth aspect, there is provided an antenna array arrangement for use with an antenna array apparatus pursuant to the first aspect, characterized in that the antenna array arrangement includes a plurality of elements disposed in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag manner in respect of a second direction relative to an elongate first direction of the rows. Optionally, in the antenna array arrangement, the plurality of phase centres are spatially disposed in a W-shape manner along the second direction.

It will be appreciated that features of the invention are susceptible to being combined in various combinations without departing from the scope of the invention as defined by the appended claims.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1 is a schematic illustration of a known antenna array arrangement;

FIGs. 2A, 2B and 2C are schematic illustrations of elements, namely "sub- apertures" or "sub-elements" , and phase centres of an antenna array arrangement pursuant to the present disclosure, wherein the antenna array arrangement is disposed in a W-formation;

FIG. 3 is a schematic illustration of signal processing apparatus for use in operation with the antenna array arrangement of FIGs. 2A to 2C for emitting electromagnetic radiation, for example for emitting electromagnetic radar radiation at a frequency of substantially 77 GHz; and

FIG.4 is a schematic illustration of signal processing apparatus for use in operation with the antenna array arrangement of FIGs. 2A to 2C for receiving electromagnetic radiation, for example for receiving electromagnetic radar radiation at a frequency of substantially 77 GHz. In the accompanying diagrams, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non- underlined number is used to identify a general item at which the arrow is pointing.

Description of embodiments of the invention

According to a first aspect, there is provided an antenna array apparatus including an antenna array arrangement that is operable with a data processing arrangement to emit electromagnetic radiation from the antenna array arrangement and/or to receive electromagnetic radiation at the antenna array arrangement, characterized in that the antenna array arrangement includes a plurality of elements disposed in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag manner in respect of a second direction relative to an elongate first direction of the rows.

The zig-zag disposition of the phase centres is capable of resulting in the polar characteristics of the antenna array arrangement including less ambiguous polar sensing directions when receiving and/or emitting electromagnetic radiation.

By "first direction" and "second direction" is intended, for example, linear directions. Alternatively, by "first direction" and "second direction" is intended, for example, circumferential directions, for example a circumferential direction around a tubular surface, a frusto-conical surface or similar, for example in a situation wherein the antenna array apparatus is disposed onto a curved surface. For example, the "first direction" is a linear direction, whereas the "second direction" is a circumferential direction, and vice versa.

By "zig-zag manner", there is denoted an alternating spatial and/or angular manner; for example, a "w" letter shape is an example of a zig-zag wherein two linear portions of the "w" letter are mutually parallel in a first direction, two linear portions of the "w" letter are mutually parallel in a second direction, and wherein the portions of the first and second directions are disposed alternately in series; joining points of the linear portions are disposed in an alternating zig-zag manner. However, it will be appreciated that a zigzag manner can include two or more alternations, for example three alternations, four alternations and so forth. Optionally, in the antenna array apparatus, the plurality of phase centres are spatially disposed in a W-shape manner along the second direction.

Optionally, in the antenna array apparatus, the plurality of phase centres are spatially disposed in a symmetrical manner along the second direction.

Optionally, in the antenna array apparatus, the second direction is substantially orthogonal to the first direction. By "substantially orthogonaF is meant in a range of 70° to 110° relative angle between the first and second directions, more optionally in a range of 85° to 95° relative angle between the first and second directions.

Optionally, in the antenna array apparatus, at least a portion of the plurality of elements is spatially disposed in a planar manner. For example, the plurality of elements is fabricated via use of a planar substrate printed circuit board.

Optionally, in the antenna array apparatus, at least a portion of the plurality of elements is spatially disposed in a curved surface. More optionally, in the antenna array apparatus, the curved surface is curved in 1 -dimension. More optionally, in the antenna array apparatus, the curved surface is curved in 2- dimensions.

Optionally, in the antenna array apparatus, the rows of elements are disposed at irregular spatial distances along the second direction. Alternatively, optionally, in the antenna array apparatus, the rows of elements are disposed at regular spatial distances along the second direction.

Optionally, in the antenna array apparatus, the elements are disposed at regular spatial distances along their respective rows. Alternatively, optionally, in the antenna array apparatus, the elements are disposed at irregular spatial distances along their respective rows.

Optionally, in antenna array apparatus, the antenna array arrangement is operable to emit and/or to receive electromagnetic radiation having principal signal components that lie in a range of 40 GHz to 200 GHz. More optionally, in the antenna array apparatus, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 50 GHz to 100 GHz. Yet more optionally, in the antenna array apparatus, the antenna array arrangement is operable to emit and/or to receive electromagnetic radiation having principal signal components of substantially 77 GHz.

According to a second aspect, there is provided a method of operating an antenna array apparatus including an antenna array arrangement that is operable with a data processing arrangement to emit electromagnetic radiation from the antenna array arrangement and/or receive electromagnetic radiation at the antenna array arrangement, characterized in that the method includes:

disposing a plurality of elements of the antenna array arrangement in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag manner in respect of a second direction relative to an elongate first direction of the rows.

By "first direction" and "second direction" is intended, for example, linear directions. Alternatively, by "first direction" and "second direction" is intended, for example, circumferential directions, for example a circumferential direction around a tubular surface, a frusto-conical surface or similar, for example in a situation wherein the antenna array apparatus is disposed onto a curved surface. For example, the "first direction" is a linear direction, whereas the "second direction" is a circumferential direction, and vice versa. Optionally, the method includes spatially disposing the plurality of phase centres in a W-shape manner along the second direction.

Optionally, the method includes spatially disposing the plurality of phase centres in a symmetrical manner along the second direction.

Optionally, in the method, the second direction is substantially orthogonal to the first direction. By "substantially orthogonaf is meant in a range of 70° to 110° relative angle between the first and second directions, more optionally in a range of 85° to 95° relative angle between the first and second directions. Optionally, the method includes spatially disposing at least a portion of the plurality of elements in a planar manner. For example, the plurality of elements is fabricated via use of a planar substrate printed circuit board.

Optionally, the method includes spatially disposing at least a portion of the plurality of elements in a curved surface. More optionally, in the method, the curved surface is curved in 1-dimension. More optionally, in the method, the curved surface is curved in 2-dimensions.

Optionally, in the method, the rows of elements are disposed at irregular spatial distances along the second direction.

Optionally, in the method, the elements are disposed at regular spatial distances along their respective rows.

Optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 40 GHz to 200 GHz. More optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components that lie in a range of 50 GHz to 100 GHz. Yet more optionally, in the method, the antenna array arrangement is operable to emit and/or receive electromagnetic radiation having principal signal components of substantially 77 GHz.

According to a third aspect, there is provided a computer program product comprising a non-transitory computer-readable storage medium having computer-readable instructions stored thereon, the computer-readable instructions being executable by a computerized device comprising processing hardware to execute a method pursuant to the second aspect.

According to a fourth aspect, there is provided an antenna array arrangement for use with an antenna array apparatus pursuant to the first aspect, characterized in that the antenna array arrangement includes a plurality of elements disposed in rows, wherein each row has a corresponding phase centre when in operation, and wherein the plurality of phase centres are spatially disposed in a zig-zag m anner in respect of a second direction relative to an elongate first direction of the rows. Optionally, in the antenna array arrangem ent, the plurality of phase centres are spatially disposed in a W-shape m anner along the second direction .

I n overview, the present disclosure seeks to provide an antenna array arrangem ent, for exam ple for providing an essential com ponent part of an antenna array apparatus, in wh ich a com bined polar receiving and/or em ission characteristic of the antenna array arrangem ent exhibits less am bigu ity in its polar directions, when in use. Conventionally, m erely increasing the num ber of elem ents in an antenna array arrangem ent does not necessarily itself address such am bigu ity, but m erely is capable of rendering the antenna array arrangem ent to exhibit relatively narrower poles of sensitivity in its polar response.

Pursuant to embodiments of the present disclosure, there is provided an antenna array arrangement which employs a phase center distribution of elements, namely "sub-elements", "apertures" or "sub-apertures", that are disposed in such a manner that centres of groups of elements are disposed spatially in a wavy manner, for example in a zag-zag manner, and more specifically in a W-shape manner, for example as illustrated in FIG. 2, wherein an antenna array arrangement is indicated generally by 10; in FIG. 2, a W-shape configuration of antenna elements 30, also referred to as "sub-elements" or "sub-apertures" as aforementioned, are disposed in rows in a Cartesian y-axis direction, for example in a row denoted by 20, wherein an "x" 40 denotes phase centres (US English: "centers") of the rows, and wherein the phase centres denoted by a plurality of "x" direction are disposed in a W-shape configuration along a Cartesian x-axis, and wherein the x-axis and y-axis are substantially mutually orthogonal; by "substantially orthogonal' is m eant in a range of 70° to 1 1 0° relative angle between the first and second directions, m ore optionally in a range of 85° to 95° relative angle between the first and second directions. However, it will be appreciated that the antenna array arrangem ent 1 0 can be disposed in other coordinate system s, for exam ple in a spatially curved coordinate system wherein at least one of the x-axis and y-axis are im plem ented as a circum ferential direction. By driving the antenna elements 30 of the antenna array arrangement via an array of driver modules 100, see FIG. 3, wherein the driver modules 100 allow adjustment of phase {0) and/or amplitude (G) of drive signals applied to the individual elements 30, a beam of radiation emitted in operation from the antenna array arrangement 10 can be steered unambiguously into a region to be interrogated by the antenna array arrangement 100. Moreover, by coupling the antenna elements 30 of the antenna array arrangement via an array of receiver modules 110, see FIG. 4, wherein the receiver modules 110 allow for amplitude adjustment and/or phase adjustment of the signals received thereat from their respective element 30, a polar direction of relatively high receiving sensitivity for the antenna array arrangement 10 can be steered in operation in an unambiguous manner. Conveniently, the driver modules 100 and/or the receiver modules 110 are coupled via high-speed heterodyne circuits ( -/) 120, to shift their signals from a lower base-band frequency to a high operating radar frequency, or to shift their signals from a high operating radar frequency to a lower base-band frequency, respectively, so that base-band signals can be handled via a data processor arrangement, for example implemented using one or more RISC (reduced instruction set computer) processors of a data processing apparatus (DSP) 130. Conveniently, phase and/or amplitude adjustments applied by the driver modules 100 and/or receiver modules 110 are also controlled from the data processing apparatus digital signal processing", DSP) 130. Optionally, the data processing apparatus {"digital signal processing", DSP) 130 includes computing hardware and is operable to execute one or more software products to control its operation.

Using the antenna array arrangem ent 1 0 , substantially all am biguous directions of polar response of the antenna array arrangem ent 1 0 can be suppressed. The am biguous directions are dependent upon a sm allest pitch along the Cartesian y- axis direction and the Cartesian x-axis direction. I n FI G. 2 B, sm allest pitches along the Cartesian y-axis direction and the Cartesian x-axis direction are denoted by "a" and "£>", respectively. Optionally, the sm allest pitches are substantially equal to a half of a wavelength (λ) of electromagnetic radiation em itted in operation from the antenna array arrangem ent 1 0. The wavy-shape antenna array arrangement 10 employs antenna partitioning, for example a zig-zag antennae partitioning, for example a W-shape antennae partitioning, namely W-shape phase-centre distribution, as is operable to provide advantageous technical characteristics, as follows:

(i) the phase centres 40 of the rows 20 are non-uniform ly or irregularly disposed in a staggered spatial arrangement, for example as illustrated in FIG. 2B; in other words, it is not possible to draw a straight line through phase centres 40 forming apexes of the W-shape phase-centre distribution, namely phase centres 40 at the ends and the middle of the W-shape phase-centre distribution;

(ii) there are provided degrees of freedom of adjustment in oblique directions relative to the Cartesian x-axis direction and the Cartesian y-axis direction, wherein the degrees of freedom allow for suppression of ambiguous lobes in the polar response of the antenna array arrangement 10; for example, all phase centres 40 of the rows 20 are mirrored along, namely symmetrical in respect of, the Cartesian y-axis direction;

(iii) the phase centres 40 are disposed in a substantially zig-zag manner, for example in a W-shape arrangement as illustrated in FIGs. 2A to 2B, although the W-shape is optionally extended to more zig-zags than two cycles, for example a WW-shape having four cycles, a WV-shape having three cycles, or a higher-order W-shape; and

(iv) the rows 20 of the elements 30 are an even number in FIGs. 2A to 2B, namely an even number of channels, although an odd number of the rows 20 of the elements 30, namely an odd number of channels, are optionally employed in an alternative configuration of the embodiments pursuant to the present disclosure, for example as shown in FIG. 2C.

Such a W-shape antennae array arrangement can be used to determine a position of a given elevated obstacle, for example, at a railway level crossing region, without having any disturbance from ambiguous directions, and simultaneously achieve greater spatial accuracy and resolution measurement capability. Such reduced ambiguity is especially useful in situations where false alarm detections are to be reduced as much as possible, whilst reliably detecting objects in a principal polar direction of sensitivity of the antenna array arrangement 10. Thus, a technical field of use of the antenna array arrangement 10 and its associated signal processing apparatus is for monitoring busy safety-critical regions, such as railway level-crossings, where false alarms can cause train delays and associated costs, whereas failure to detect objects in a principal polar direction of sensing can cause potential accidents to arise, for example collisions between trains and objects at the railway level-crossings that could potentially give rise to fatalities. However, other uses of the antenna array apparatus 10 are feasible, for example in vehicle anti-collision safety devices, in intruder alarms, in drone detection systems, in autonomous vehicle guidance systems, in satellite systems, in weapons systems and so forth.

Moreover, the W-shape antenna array arrangement 10, when mounted at a front of a road vehicle, can be used to detect whether or not an obstacle is an elevated or non-elevated object at a centre of a roadway, for example, or at a side of the roadway, for example a tunnel-wall, one or more road-side fences, one or more parked cars, one or more trucks, one or more vehicles in side roads attempting to pull out from the side roads in a main roadway, and so forth. Thus, the antenna array arrangement 10 pursuant to the present disclosure is susceptible to being employed in road vehicle applications such as vehicle collision avoidance, vehicle collision warning, automatic vehicle braking systems, automatic vehicle steering systems, and similar. Optionally, the antenna array arrangement 10 can be used to monitor road surface conditions, for example for detecting a presence of gravel, ice or snow and provide corresponding vehicle driver warnings; for example, the antenna array arrangement 10 can be used to detect pot-holes in road surfaces and provide corresponding driver warnings to avoid the pot-holes and thereby reduce potential vehicle axle damage or wheel damage.

Alternative variations of the antenna array arrangement 10 are capable of being implemented. For example, the elements 30 can be disposed on a planar surface or on a curved surface. The curved surface can be curved in 1- dimension, or even 2-dimensions. The rows 20 of the elements 30 are conveniently, for example, implemented at an edge region of a printed circuit board, such that the antenna array arrangement 10 is conveniently implemented as a stacked arrangement of printed circuit boards. Optionally, the elements 30 of a given row 20 are disposed in a straight axis; alternatively, optionally, the elements 30 of a given row 20 are disposed along a curved path. Optionally, the elements 30 are disposed at regular spatial distances along their corresponding rows 20; alternatively, the elements 30 are disposed at irregular spatial distances along their corresponding rows 20; yet alternatively, some of the rows 20 have their elements 30 disposed at regular distances along their rows 20, whereas other of the rows 20 have their elements 30 disposed at irregular distances along their rows 20.

The antenna array arrangement 10 is capable of emitting and/or receiving electromagnetic radiation having a frequency in a range of 40 GHz to 200 GHz, and more optionally in a range of 50 GHz to 100 GHz, and yet more optionally at substantially 77 GHz. Such high operating frequencies for the emitted and/or received electromagnetic radiation enables the antenna array arrangement 10 to be implemented in a highly compact manner, for example for being deployed in a bumper or dashboard of a road vehicle, or within a nose cap of a missile, mortar, or similar type of high-velocity projectile.

Optionally, the antenna array arrangement 10 is implemented by selectively using elements of a regular rectilinear array of elements, for example a regular square-shaped array of elements, a regular tubular array of elements, a regular spherical array of elements, and so forth. The elements 30 are optionally implemented as patch antennae. Alternatively, the elements 30 are implemented as miniature dipole antennae whose output or drive signals are coupled via optical fibres therefrom and/or thereto, respectively; the miniature dipole antennae, in such case, are each provided with an optical-to-electrical transceiver integrated circuit, wherein the transceiver integrated circuit is energized in operation by applying optical radiation thereto. Such an implementation using optical fibres enables the antenna array apparatus 10 to be implemented as a 3-dimensional array providing exceptionally selective polar emission and/or receiving characteristics in a very compact overall physical size for the antenna array apparatus 10; such an arrangement can be mounted, for example, in a nose cone of an aircraft for providing a high-resolution agile radar system, for example suitable for military airborne vehicles and radar defence systems (for example, missile tracking systems). Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "consisting of", "have", "is" used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.