RADIO APPARATUS

The invention relates to radio apparatus incorporating antenna diversity.

Antenna diversity is well known as a method of improving communication quality in a system in which radio signals are subjected to multipath propagation. Some configurations of antenna diversity provide for selection between a plurality of antennas, either for transmission or for reception, and other configurations provide for the combining of signals received via a plurality of antennas. The latter category of configuration requires a comparatively complex receiver capable of signal combining. The former category of configuration, referred to as antenna selection diversity, requires a comparatively simple receiver and is most relevant to the present invention.

An example of a radio apparatus employing antenna selection diversity is illustrated in Figure 1. It comprises a transceiver (Tx/Rx) 10 coupled to a selector switch 16. The selector switch 16 is controllable to couple either one of two antennas 12, 13 to the transceiver 10. Therefore the antenna can be selected both for transmission and for reception. A controller (not illustrated) controls the selector switch 16, the selection being based on received signal quality.

Radio apparatus equipped to operate with more than one signal type is also known, for example mobile phones equipped to transmit and receive not only mobile phone signals for communication with a mobile phone network, but also Bluetooth™ signals for communication with a Bluetooth™ enabled headset or personal computer, and mobile phones equipped to also receive Global Positioning System (GPS) signals. Other combinations can be envisaged, for example a mobile phone equipped to also receive television signals. Such apparatus is referred to in this specification as a "dual signal apparatus", and is characterised by the ability to transmit and receive

simultaneously different signals conveying different data bits. The term "dual signal apparatus" is not intended to exclude the possibility that the apparatus is adapted to transmit and receive more than two signals simultaneously.

An example of a dual signal apparatus is illustrated in Figure 2. It comprises two transceivers 10, 11 each coupled to respective antennas 12, 14. One of the transceivers may be replaced by a receiver, for example as would be required for reception of broadcast signals from a broadcast system where no return transmission is required by that system. As shown in Figure 2, a dual signal apparatus may comprise at least one antenna for each receiver or transceiver to provide isolation between different signals transmitted and received simultaneously. It would be possible for the two transceivers 10, 11 to use a common antenna, but in this case filters would need to be incorporated to ensure adequate isolation between the two transceivers 10, 11. Such filters are undesirable because they would increase pass-band loss and reduce transmitter efficiency, as well as increasing component count and cost.

In order to improve the communication quality of the dual signal apparatus, the antenna diversity illustrated in Figure 1 may be applied to the apparatus illustrated in Figure 2. The resulting apparatus architecture is illustrated in Figure 3, where elements common to Figure 3 and to Figure 1 or 2 have being assigned identical reference numerals. In order to provide antenna diversity for two transceivers 10, 11 , four antennas 12, 13, 14, 15 are provided and a dual selector switch 18 comprising two selector switches 16 is required. A controller for controlling the switches is not illustrated, but each selector switch 16 would be controlled independently because, in general, the multipath propagation experienced by each signal would be independent. The apparatus illustrated in Figure 3 has the disadvantage of requiring four antennas, which increases the size of the apparatus.

An object of the invention is to provide an improved radio apparatus adapted for dual signal operation and incorporating antenna diversity.

According to the invention there is provided a radio apparatus comprising: first and second antennas; a first transceiver comprising a first transmitter and a first receiver; a second receiver; switching means arranged to provide selectable first and second states, wherein in the first state an output of the first transmitter is coupled to the first antenna and is not coupled to the second antenna, and an input of the second receiver is coupled to the second antenna and is not coupled to the first antenna, and in the second state the output of the first transmitter is coupled to the second antenna and is not coupled to the first antenna, and the input of the second receiver is coupled to the first antenna and is not coupled to the second antenna; and control means adapted to select between the first and second states for simultaneous transmission by the first transmitter and reception by the second receiver.

The apparatus operates to ensure that simultaneous transmission and reception of different signals takes place via different antennas. The invention provides a dual signal apparatus incorporating antenna diversity but requiring fewer antennas than the apparatus illustrated in Figure 3, thereby enabling a more compact apparatus, and simplifying the requirement for providing isolation between a transmitter and receiver. In order to benefit from these advantages, the apparatus is unable to select independently antennas for simultaneous transmission and reception of different signals. However, such a constraint is acceptable in an environment where, for example, an arbitrary choice of antenna for a signal is more likely to result in an acceptable signal level than an unacceptable signal level, which is expected to be the case in the majority of locations within a radio system's coverage area. In one embodiment, when the first and second receivers are receiving simultaneously, the apparatus is adapted to couple the first and second

receivers to different ones of the first and second antennas. Such an embodiment has the advantage of being simple to implement.

In another embodiment, when the first and second receivers are receiving simultaneously, the apparatus is adapted to couple either of the first and second receivers to either of the first or second antennas independently.

Such an embodiment has the advantage of providing independent receive diversity for both receivers.

The selection of states by the control means may be dependent on an indication of a signal quality. A variety of alternative different signal quality criteria may be employed to select antennas. For example, the indication of signal quality may be generated from a quality parameter measured on one or more of a signal received by the first receiver and a signal received by the second receiver, via either or both of the first and second antennas. In this way, the apparatus may perform the selection to optimise its own reception quality.

The selection of states by the control means may be in response to a value of a signal received via at least one of the first and second antennas. In this way, the apparatus may perform the selection to optimise reception by an external device that receives a signal transmitted by the apparatus and that transmits to the apparatus a command to change state or an indication of signal quality measured by the external device.

A combination of the above state selection criteria may be used.

The invention will now be described, by way of example only, with reference to the accompanying drawings wherein:

Figure 1 is a block schematic diagram of a prior art antenna diversity apparatus;

Figure 2 is a block schematic diagram of a prior art dual signal apparatus; Figure 3 is a block schematic diagram of a dual signal apparatus with antenna diversity;

Figure 4 is a block schematic diagram of an apparatus in accordance with the invention;

Figure 5 is a flow chart of a method of operating the apparatus of Figure 4; and Figure 6 is a block schematic diagram of a further apparatus in accordance with the invention.

Referring to Figure 4 there is illustrated a first embodiment of a radio apparatus 400 in accordance with the invention, comprising a first antenna 42, a second antenna 44, a first transceiver 40 comprising a first transmitter 60 and a first receiver 61 , and a second receiver 62. The first transceiver 40 may be, for example, a mobile phone transceiver for communicating with a GSM (Global System for Mobile Communication) network, or a UMTS (Universal Mobile Telecommunication System) network, or other mobile phone network. The second receiver 62 is adapted to receive different signals conveying different data bits than the first receiver 61. For example, the second receiver 62 may be a broadcast receiver for receiving digital television signals such as DVB (Digital Video Broadcast) or specifically DVB-H (Digital Video Broadcast - Handheld) signals, or any other broadcast signals. There is a switching means 45, 46 comprising an antenna selector means 46 and a routing means 45. The antenna selector means 46 functions as a changeover switch, being arranged to couple either of the antennas 42 or 44 to the first transceiver 40 by way of the routing means 45 and to couple the other of the antennas 42 or 44 to the second receiver 62. The routing means 45 may be a switch for coupling either one of the first transmitter 60 and the first receiver 61 to the antenna selector means, if the first transceiver 40 is adapted for half duplex operation, i.e. it can transmit or receive signals, but not simultaneously. Half duplex operation may be used in a time division multiple access (TDMA) system where transmission and reception need not occur simultaneously, even though operation may give a user the impression of full duplex operation. Alternatively, the routing means 45 may be a duplexer if the first transceiver 40 is adapted for full duplex operation, i.e. it can transmit and

receive signals simultaneously, or even if the first transceiver 40 is adapted for half duplex operation.

The switching means 45, 46 provides a first state in which an output of the first transmitter 60 is coupled to the first antenna 42 and is not coupled to the second antenna 44, and an input of the second receiver 62 is coupled to the second antenna 44 and is not coupled to the first antenna 42, and a second state in which the output of the first transmitter 60 is coupled to the second antenna 44 and is not coupled to the first antenna 42, and the input of the second receiver 62 is coupled to the first antenna 42 and is not coupled to the second antenna 44. The selection of the state of the switching means 45, 46 is controlled by a control means 50, such as a microcontroller. The control means 50 is adapted to select one of the first and second states when simultaneous transmission by the first transmitter 60 and reception by the second receiver 62 is required. Optionally, coupled to the control means 50, there is a signal quality measurement means 52, 53 for measuring a quality parameter of at least one of a signal received by the first receiver 61 and a signal received by the second receiver 62. The quality parameter may be one or more of: signal level; signal to noise ratio; signal to interference ratio, bit error rate, frame error rate, or any other parameter representative of signal quality. The control means 50 selects the state of the switching means 45, 46 according to the value of the measured quality parameter.

Alternatively, or additionally, the apparatus 400 may receive from an external device a signal comprising a command, or an indication of quality of a signal transmitted by the apparatus 400 and received by the external device, and employ this command or indication to select the state of the switching means 45, 46. For example, an external device may report when the signal that it receives from the apparatus 400 falls below a predetermined quality threshold for a predetermined time duration. Referring to Figure 5, there is illustrated an example of a method of selecting the state of the switching means 45, 46. By way of example, the first transceiver 40 is considered to be a GSM transceiver, and the second receiver

62 is considered to be a DVB receiver. The method commences at step 100 where the initial state of the switching means 45, 46 is selected arbitrarily, thereby arbitrarily selecting an antenna for each of the first transceiver 40 and the second receiver 62. Flow proceeds to step 110 where a test is made to determine whether the apparatus is required currently to operate as a GSM phone and/or a DVB receiver, according to user requirements indicated by means of a user interface. If the apparatus is required to operate only as a GSM phone, flow proceeds to step 120 where a signal quality measurement is made on a received GSM signal by the signal quality measurement means 52, such as a received signal strength indication (RSSI) circuit, and a test is made to determine whether the measured value exceeds a predetermined value T _G S _M - If the measured value exceeds the predetermined value T _G S _M flow returns to step 110. The current state of the switching means is maintained, and the test at step 110 is repeated in a loop to detect when the user indicates a requirement to receive DVB signals.

If the test at step 120 indicates that the measured value does not exceed the predetermined value TQS _M , flow proceeds to step 130 where the antennas are interchanged, such that the other antenna is now coupled to the first transceiver 40. Then at step 140 the same test as step 120 is made to determine whether the GSM signal now being received by the other antenna satisfies the quality criterion. If the measured value exceeds the predetermined value TQS _M flow returns to step 110.

If the test at step 140 indicates that the measured value does not exceed the predetermined value TQS _M , then this indicates that neither antenna 42 or 44 is receiving a GSM signal of sufficient quality to exceed the quality threshold requirement TQS _M and so at step 150 the antenna receiving the better quality GSM signal is selected for use by the first transceiver 40. Flow then returns to step 110. If at step 110 the apparatus is required to operate only as a DVB receiver, flow proceeds to step 160 where a signal quality measurement is made on a received DVB signal by the signal quality measurement means 53,

such as a received signal strength indication (RSSI) circuit, and a test is made to determine whether the measured value exceeds a predetermined value TDVB- If the measured value exceeds the predetermined value T _D VB flow returns to step 110. The current state of the switching means is maintained, and the test at step 110 is repeated in a loop to detect when the user indicates a requirement to receive GSM signals.

If the test at step 160 indicates that the measured value does not exceed the predetermined value T _DVB , flow proceeds to step 170 where the antennas are interchanged, such that the other antenna is now coupled to the second receiver 62. Then at step 180 the same test as step 160 is made to determine whether the DVB signal currently being received by the second receiver 62 satisfies the quality criterion. If the measured value exceeds the predetermined value T _DVB flow returns to step 110.

If the test at step 180 indicates that the measured value does not exceed the predetermined value T _DVB , then this indicates that neither antenna 42 or 44 is receiving a DVB signal of sufficient quality to exceed the quality threshold requirement T _DVB and so at step 190 the antenna receiving the better quality DVB signal is selected for use by the second receiver 62. Flow then returns to step 110. Other antenna selection criteria may be used. For example, when the apparatus is required to operate in only one mode, as either a GSM mobile phone or a DVB receiver, the control means 50 may operate to select the antenna, 42 or 44, that provides the higher quality signal, rather than selecting the antenna that provides a signal that exceeds the appropriate quality threshold, TQSM or TDVB-

If the test at step 110 indicates that the apparatus is required to operate as both a GSM mobile phone and a DVB receiver simultaneously, flow proceeds to steps 160 to 190 wherein the decision about which antenna to couple to the second receiver 62 is based on satisfying the selection criterion for the DVB signal at steps 160 and 180; the first transceiver 40 is coupled to the antenna, 42 or 44, that is not used by the second receiver 62.

Alternatively, if the test at step 110 indicates that the apparatus is required to operate as both a GSM mobile phone and a DVB receiver simultaneously, flow may proceed to steps 120 to 150 wherein the decision about which antenna to couple to the first transceiver 40 to is based on satisfying the selection criterion for the GSM signal at steps 120 and 140; the second receiver 62 is coupled to the antenna, 42 or 44, that is not used by the first transceiver 40.

Alternatively, if the test at step 110 indicates that the apparatus is required to operate as both a GSM mobile phone and a DVB receiver simultaneously, the selection criterion may take account of the quality of both the received GSM signal and the received DVB signal. For example, such a scheme may operate to ensure that, where possible, both the GSM signal and the DVB signal are received at a level above the appropriate quality threshold, TGSM or TDVB- Alternatively or additionally, the selection criteria may take into account a value of a signal received by either of the first and second receivers 61 , 62 as described above. In this way, the apparatus may perform the selection to optimise reception by an external device that receives a signal transmitted by the apparatus and that transmits to the apparatus a command to change state or an indication of signal quality measured by the external device.

Reverting to Figure 4, as described above, the control means 50 is adapted to select one of the first and second states when simultaneous transmission by the first transmitter 60 and reception by the second receiver 62 is required. If the apparatus 400 is required, according to the requirements of the systems on which the apparatus 400 is operating, or according to user requirements, to receive simultaneously different signals by the first receiver 61 and the second receiver 62, optionally the control means 50 may be adapted to select one of a third and fourth state. In the third state an input of the first receiver 61 is coupled to the first antenna 42 and is not coupled to the second antenna 44, and the input of the second receiver 62 is coupled to the second antenna 44 and is not coupled to the first antenna 42. In the fourth state the input of the first receiver 62 is coupled to the second antenna 44 and

is not coupled to the first antenna 42, and the input of the second receiver 62 is coupled to the first antenna 42 and is not coupled to the second antenna 44. The control means 50 is adapted to select between the third and fourth states for simultaneous reception by the first and second receivers 61 , 62 using one or more of the selection criteria described above.

If the first transceiver 40 switches back and forth between transmitting and receiving, i.e. half duplex operation, the control means 50 will switch the apparatus 400 between one of the first and second states and one of the third and fourth states. Typically, but not exclusively, reception by the first receiver 61 and transmission by the first transmitter 60 may, for most of the time, both take place via a common antenna, although the particular selection of antenna will change as propagation conditions change. This correspond to the apparatus using for most of the time states one and three and states two and four. Optionally, re-selection of states may take place at changeover between transmission and reception.

If the first transceiver 40 operates simultaneous transmission by the first transmitter 60 and reception by the first receiver 61 , i.e. full duplex operation, then the apparatus 400 as described with reference to Figure 4 will operate simultaneously in states one and three or simultaneously in states two and four, and the control means 50 will control the selection of these pairs, depending on one or more of the selection criteria described above.

Referring to Figure 6 there is illustrated a second embodiment of a radio apparatus 500 in accordance with the invention. Except for the differences described below, the elements of the second embodiment are identical to those elements of the first embodiment described above with reference to

Figure 4 and having identical reference numerals. The differences are:

(i) The antenna selector means 46 of Figure 6 functions as a pair of selector switches 48, configured to enable the first transceiver 40 and the second receiver 62 to each be coupled to either antenna 42, 44 independently, including coupling to the same or different antennas 42, 44.

(ii) The switching means 45, 46 in the second embodiment provides the first, second, third and fourth states as described above in relation to the first embodiment, and additionally provides a fifth and sixth state. In the fifth state the input of the first receiver 61 and the input of the second receiver 62 are coupled to the first antenna 42 and are not coupled to the second antenna 44. In the sixth state the input of the first receiver 61 and the input of the second receiver 62 are coupled to the second antenna 44 and are not coupled to the first antenna 42. The control means is adapted to select one of the first and second states when simultaneous transmission by the first transmitter 60 and reception by the second receiver 62 is required, and one of the third, fourth, fifth or sixth states when simultaneous reception by the first and second receivers 61 , 62 is required, using one or more of the selection criteria described above.

(iii) If the first transceiver 40 is capable of full duplex operation, i.e. simultaneous transmission by the first transmitter 60 and reception by the first receiver 61 , then one of the third, fourth, fifth or sixth states may be selected simultaneously with one of the first and second states, provided that the configuration of both the selected states is complied with. For example, selection of the first and third states simultaneously will couple the first transmitter 60 and the first receiver 61 to the first antenna 42 and the second receiver 62 to the second antenna 44. As another example, selection of the first and sixth states simultaneously will couple the first transmitter 60 to the first antenna 42 and the first and second receivers 61 , 62 to the second antenna 44. Thus transmission and reception by the first transceiver 40 may take place simultaneously via different antennas. An example of a combination of states that cannot be implemented because of conflicting states is the simultaneous combination of states 1 and 5.

The embodiment of Figure 6 may operate according to the method described above with respect to Figure 5, or may use variations of the method that employ the additional fifth and sixth states.

At least one of the first and second receivers 61 , 62 may be adapted to receive a signal which is partitioned into time frames, such as a GSM signal or a DVB-H signal. In this case the control means 50 may be adapted to, while such a signal is being received, re-select the state of the switching means 45, 46 only at time frame boundaries, such that the received signal is not corrupted by the re-selection. The first transceiver 40 may be adapted to alternately transmit and receive in a time division mode, and may include periods when neither transmission or reception occurs, during which periods power saving may be implemented. Similarly, the second receiver 62 may be adapted to alternate periods of receiving with periods when no reception occurs, thereby enabling power saving during periods of no reception. The control means (50) may be adapted to re-select the state of the switching means 45, 46 only while one or more of the following conditions are satisfied: the first transmitter 60 is not transmitting; the first receiver 61 is not receiving; the second receiver 62 is not receiving. Optionally the apparatus, 400 or 500, may comprise a second transceiver comprising the second receiver 62 and a second transmitter. In this case the control means 50 and switching means 45, 46 may be further adapted to ensure that simultaneous transmission by the first transmitter 60 and the second transmitter takes place via different ones of the antennas 42, 44, thereby avoiding simultaneous transmission via a common antenna, 42 or 44, and may be adapted to ensure that simultaneous transmission by the second transmitter and reception by the first receiver 61 takes place via different ones of the antennas 42, 44, thereby avoiding simultaneous transmission by the second transmitter and reception by the first receiver 61 via a common antenna, 42 or 44.

The measurement means 52, 53 may be integral with the respective receivers 61 , 62 or separate.

The switching means 45, 46 may be implemented using electronic or electromechanical technology.

Although the invention has been described with reference to two antennas and two receivers, and optionally two transceivers, the use of more antennas, receivers or transceivers is not precluded.

Although embodiments have been described with particular reference to GSM and DVB, the invention may also be used in conjunction with other wireless systems, for example wireless local area networks (WLAN) or Digital Audio Broadcast (DAB). Although example criteria have been described for selecting the states of the apparatus, 400 or 500, the use of other selection criteria is not precluded.

In the present specification and claims the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Further, the word "comprising" does not exclude the presence of other elements or steps than those listed.

The inclusion of reference signs in parentheses in the claims is intended to aid understanding and is not intended to be limiting.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art of radio communications and antenna diversity schemes and which may be used instead of or in addition to features already described herein.