GB2465561A

GB2465561A - Method, device and computer program for receiving signals using multi-beam antenna arrays

Info

Publication number: GB2465561A
Application number: GB0821164A
Authority: GB
Inventors: Philippe Le Bars; Alain Caillerie
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2008-11-19
Filing date: 2008-11-19
Publication date: 2010-05-26
Anticipated expiration: 2028-11-19
Also published as: GB0821164D0; GB2465561B

Abstract

An electromagnetic signal receiving method or a device or a computer program with means suitable for implementing such a method comprises receiving a radio frequency signal via a group of antenna elements. The received signal is processed by first and second beam formers such that they correspond to first and second respective beam patterns 210, 220, during a tracking period. The first beam former has a substantially unchanged beam pattern 210 whilst the second beam former has a beam pattern 220 adjusted to track changes in the direction of arrival, if any, of the received RF signal, during the tracking period. Following the tracking period, the first beam former beam pattern 210 is updated 230 in accordance with that of the adjusted second beam former 220 and is then used to process the RF signal received in the period following the tracking period. Alternate tracking and receiving periods may be employed and the first and second beam formers may relate to the same group of antenna elements or to different respective groups of antenna elements. Some or all of the antenna elements may be used during a signal receive period. Such a receiving method can be used in a wireless speaker to receive wireless audio system.

Description

TITLE OF THE INVENTION

Method, device and computer program for receiving signals using multi-beam antenna arrays

BACKGROUND OF THE INVENTION

Technical field of the invention

The present invention relates to radio communication systems. The present invention is particularly applicable to radio communication systems employing antenna arrays.

Description of the background art

Wireless systems using electromagnetic signals with a wavelength of the order of a few millimeters, typically in the 60 Ghz band, are well suited for transporting larg amounts of data over short distances as the allowed bandwidth is large. A wireless system of this kind can achieve very high bit rates, e.g. above one gigabit per second, and thus makes it suitable for connecting several audio and video devices in a home network

for example.

Signals with these characteristics, hereinafter referred to as milhmeter band signals, have different propagation characteristics from lower frequency signals. In the millimeter band, most of the useful energy that reaches receiving antenna comes from the S...

energy radiated in line of sight by the transmitting antenna. This makes the use of adjustable directional antennas in such wireless systems very efficient as they are * * capable of adapting the antenna gain characteristics based on the direction of interest.

In an emitting phase, an electronically adjustable directionaj antenna allows control of how the electromagnetic beam spreads out as it get farther from its point of origin. It is :::: : thus possible to steer the beam to the direction of a receiver for example. In receiving * "25 phase, an electronically adjustable directional antenna is able to adapt the antenna gain based on the direction of arrival of a received signal. In either phase, it is thus a requirement to know the direction of transmission or the direction of arrival of a signal to adapt the antenna gain characteristics accordingly.

In wireless systems comprising wireless devices having fixed positions, it's enough to have predefined antenna settings adapted for each direction corresponding to a possible pair of communicating wireless devices. This technique allows fast switching of a communication from one wireless device to another, compared to automatic determination of direction of arrival of the radio wave each time an emitter changes its position for

example.

Predefining antenna settings can be performed during an initialization phase before any communication in the wireless system actually starts. This initialization can be performed using the following algorithm. Sequentially, every wireless device transmits a radio wave during a predetermined period of time using a wide beam radiation pattern or an omnidirectional pattern. During that predetermined period of time, every other wireless device performs a scan of the full available range of angles using a narrow beam and measures the received signal strength. Antenna settings corresponding to the angle providing the maximum signal strength are saved along with the associated angle.

While running the above algorithm before any communication over the wireless network actually starts may be acceptable, updating the settings for a given antenna during system operation may cause serious quality degradation or interruption of service.

Indeed, in a wireless network involving not fixed devices like for example a wireless audio system, it is likely that a wireless device, e.g. a speaker, will be moved, either by accident or deliberateiy, during system operation because wireless devices are usually within reach of home occupants and speakers are likely to be knocked or otherwise disturbed.

It is thus desirable to provide an unobtrusive method to update antenna angles while the system is receiving signals in order to avoid service interruption.

Furthermore, the applicant realized that the automatic control mechanisms of the gain (AGC) and the phase of the received radio signals that need to be performed either Continuously or at regular time intervals by the radio modem may interfere with the *::::* antenna angle adjustment method as this latter has effect on the reception antenna gain also.

Indeed, the automatic control of modem parameters (gain and phase) and antenna gain can be seen as nested loops that need to be appropriately controlled to avoidany instability in the parameters determination and consequently to avoid reception quality ::: degradation.

SUMMARY OF THE INVENTION

The present invention has been made to address the drawbacks of prior art method as described above.

Particularly, the present invention has been made for providing a method of receiving radio signals that allows the tracking of changes in the reception angle of a directional antenna whilst maintaining the communication uninterrupted.

A further objective of the invention is to provide a method of receiving radio signals that allows to track changes in the reception angle without disturbing the automatic control of the radio modem parameters.

Yet a further objective of. the invention is to provide a method of receiving radio signals that allows to track rapid and/or frequent changes in the reception angle.

According to a first aspect of the present invention, there is provided a method of receiving comprising: receiving a radio signal in a tracking period; applying first beamformer processing to the radio signal received in said tracking period, the first beamformer processing comprising obtaining respective antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a first set of weighting coefficients so as to produce a first processed signal corresponding to a first reception beam pattern; applying second beamformer processing to the radio signal received in said tracking period, the second beamformer processing comprising obtaining respective antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a second set of weighting coefficients so as to produce a second processed signal corresponding to a second reception beam pattern; during the tracking period, adjusting the second set of weighting coefficients so as to track changes, if any, in a direction of arrival of the received radio signal, whilst maintaining the first set of weighting coefficients substantially unchanged; following the tracking period, updating the first set of weighting coefficients in dependence upon the adjusted second set of weighting coefficients and applying the first beamformer processing to the radio signal received following the tracking period using the updated first set of weighting coefficients.

This has the advantage of ensuring a simultaneous reception of signals and an update of the orientation of the array antenna so that to be kept continuously pointing to .: 30 the transmitter.

Furthermore, as the first set of weighting coefficients is maintained substantially unchanged, automatic control of radio modem parameters can be performed safely and accurately during the tracking period.

The control of parameters is not performed at the expense of missing any necessary angle update since the first set of weighting coefficients is still updated in dependence upon the adjusted second set of weighting coefficients. This allows to track rapid and/or frequent changes in the reception angle of the radio signals.

Advantageously, the receiving method further comprising applying the second beamformer processing to the radio signal received following the tracking period and combining the first and second processed signals. The gain of the combination of the processed signals is thus increased.

According to one embodiment of the invention, the receiving method having a receiving period following said tracking period, the first set of weighting coefficients being updated at or prior to a start of the receiving period and being used for applying the first beamformer processing to the radio signal received over the course of the receiving period. The reception during the receiving period is thus performed with the most up-to-date first and second set of weighting coefficients.

In a preferred embodiment of the invention, it is possible to alternate such tracking and receiving periods to adapt for example to a physical layer implementing a time division multiplexing (1DM).

In a TOM physical layer where received physical data units contain a preamble, a header and payload data, the tracking period is advantageously synchronized with the reception of the preamble and the header, and the receiving period is synchronized with the reception of payload data.

Thus, during the tracking period, the first processed signal is to be used by the radio modem to control the reception parameters (AGC, etc.) and the second processed signal is to be used to receive the header and payload data, whereas during the receiving period, both the first and the second processed signals contribute to the reception of payload data. * **

In another embodiment of the invention, the first beamformer processing the antenna signals are obtained from a first such group of antenna elements and in the second beamformer processing the antenna signals are obtained from a second such group of antenna elements, different from said first group.

This allows to increase the reception gain. It allows also to adapt to an antenna array composed of different panels to cover a broader range of angles, where the first and second group of antenna elements are disposed over different panels.

* *0 When the first and second groups of antenna elements have different directions, the first set of weighting coefficients are updated in dependence upon the different directions as well as upon the adjusted second set of weighting coefficients.

In yet another embodiment of the invention, in both the first beamformer processing and the second beamformer processing, the antenna signals are obtained from the same -group of antenna elements.

This makes the updating of the first set of weighting coefficients in dependence upon the adjusted second set of coefficients easy and straightforward as it consists in copying the coefficients.

Further aspects of the present invention can provide a program, a receiving device and wireless speaker apparatus. A program embodying the present invention can be provided by itself or may be carried by a carrier medium. The carrier medium may be a storage medium such as a memory device. The carrier medium may also be a transmission medium such as a signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic configuration illustrating the functional blocks for receiving signals through a multi-beam antenna array according to one embodiment of the invention.

Figure 2 depicts a flow chart illustrating the steps carried out by the different functional units of figure 1.

Figure 3 depicts a flow chart illustrating an example of updating the weighting coefficients associated with a first group of antenna elements from those of a second group of antenna elements.

Figure 4 illustrates one way of disposing the different groups of antenna elements over a multi-beam array antenna.

Figure 5 shows a coordinate system that helps illustrate the reception of signals by *:-::* an array antenna.

Figure 6 illustrates an example of a physical layer that can be used for the reception of signals in a wireless network according to one embodiment of the invention.

Figure 7 depicts a flow chart illustrating a method of receiving signals in a wireless TDM system according to one embodiment of the invention.

Figure 8 is a schematic configuration illustrating the functional blocks for receiving S...

signals through one group of antenna elements according to another embodiment of the invention.

Figure 9 illustrates a schematic configuration of a communication device adapted to embody the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following, a detailed description will be given of embodiments of the present invention with reference to the accompanying drawings.

The multi-beam antenna array is formed by at least a first group of antenna elements lOOa and a second group of antenna elements bOb. Each group of antenna elements can be separately controlled by a beam control unit liOa/llOb for a selective reception of signals in a particular direction.

For the first group of antenna elements, the selective reception is accomplished by selecting weighting coefficients (w1, .., We,) applied to each signal path from the different elements of the first group so that to increase the gain of the antenna in a certain angular direction. The desired weighting is selected by iteratively changing the weights through a feedback loop (tracking mode) comprising an adjustment unit 130a and a weights control unit lila. The aim of the feedback loop is to maximize signal-to-noise ratio (SNR) at the output of the adjustment unit 130a.

The second group of antenna elements is controlled similarly to the first group through the selection of a second set of weighting coethcients (w1', .., w).

The tracking mode for a given group of antenna elements is activated by setting the respective switch 120a or 120b in a tracking position p2. The receiving mode is activated by setting the switch 120a or 120b in a receiving position p1 to deliver the received signals to the reception unit 140.

Setting the reception of signals in a particular direction for a given group of antenna elements can be forced by inputting via input 114a/114b the appropriate weights * ** representative of the desired direction in control unit lila/il lb. A conversion unit 112a/112b is provided to convert a given angular direction into a set of weights that can be inputted to the weights control unit lila/Ill b.

Conversely, the weights that are applied by the controller llla/lllb and in use in the adjustment unit 130a/130b can be read via output 115a/l 15b and converted by means of the conversion unit 112a/112b to obtain the corresponding angular direction.

An antenna controller (not shown in the figure) is provided to properly control the different groups of antenna elements so that to allow the reception of signals while maintaining the different beams correctly directed towards the emitting point. This control includes on one hand the selection between receiving and tracking modes for the different groups of antenna elements and on the other hand the weighting coefficients to be input to or read from the weights control units.

The signals resulting from the beam control units 11 Oa/i bOb operating in receiving modes are combined to increase the gain and the combined signals are delivered to the receiver unit 140.

Delay units 150 are provided prior the combining of signals to cope with the possible phase difference between the different signals. This phase difference may be created if one group of antenna elements is at a different distance from the source of the signals (emitting point) than one other group of antenna elements.

Figure 2 depicts a flow chart illustrating the steps carried out by the different functional units of figure 1 when processing signals received via the different groups of antenna elements.

In step 210, a first beam is formed for receiving signals using the first group of antenna elements iOOa. The receiving of signals is ensured by activating the receiving mode (switch 120a in receiving position p1).

When the whole system is first started, the weights control unit lila may be initialized with weighting coefficients stored in a memory for example. During operation, the weighting coefficients in use in the adjustment unit 1 30a are for example those most recently updated, either when operating in tracking mode or by means of an external update via the input 11 4a of the weights control unit.

In step 220, a second beam is formed for tracking the direction of arrival of the signals using the second group lOOb of antenna elements. The switch l2Ob is set to the tracking position p2. The tracking allows to update the weighting coefficients associated with the second group of antenna elements lOOb.

In step 230, the updated weighting coefficients associated with the second group of * antenna elements lOOb are used to update the weighting coefficients associated with the first group of antenna elements lOOa, taking into account the relative spatial location I.. S between the first and the second groups of antenna elements.

In the present example there are two groups of antenna elements. In another *5*S*U * 25 embodiment of the present invention, more than two groups of antenna elements may be * provided, with more than one group operating in receiving mode and at least one group operating in tracking mode. The updated weighting coefficients associated with the group *.** . : operating in tracking mode are used to update the weighting coefficients associated with * the other groups according to step 230 above.

In yet another embodiment, also having more than two groups of antenna elements, more than one group can operate in tracking mode and at least one group can operate in receiving mode. In such a case, it is possible to select one of the groups operating in tracking mode to use its weighting coefficients.

In another embodiment, a plurality of groups operating in tracking mode are used for producing respective sets of updated weighting coefficients associated with The group operating in receiving mode. The set of weighting coefficients that is to be actually applied for updating the weights of the group operating in receiving mode may be calculated as -8.-.

the average of the sets of coefficients produced by the plurality of groups operating in tracking mode.

Figure 3 depicts a flow chart illustrating an example on how the weighting coefficients associated with the second group of antenna elements I DOb are used to update the weighting coefficients associated with the first group of antenna elements lOOa.

In step 310, the reception angle of the signals is determined based on the weighting coefficients associated with the second group of antenna elements lOOb. This is performed by means of the conversion unit 11 2b according to algorithms known in the art.

For example, elaborated techniques like ESPRIT or MUSIC may be used. The conversion can also be performed by means of a pre-stored table containing the correspondence between angles and coefficients.

The determined reception angle is relative to the antenna elements of the second group 1 OOb, for example taking as reference the plane containing those antenna elements.

In step 320, the reception angle of the signals relative to the first group of antenna elements is calculated using the determined reception angle and the relative spatial location (angle and distance) between the first and the second groups of antenna elements.

In step 330, the weighting coefficients associated with the first group of antenna elements are set based on the calculated reception angle. This may be performed by converting back the reception angle of the signals relatively to the first group of antenna S...

elements into weighting coefficients by means of the conversion unit 112a. These weighting coefficients are then inputted in the weights control unit lila through input *IS*S* * 25 115a.

a.....

* S Figure 4 illustrates one way of disposing the different groups of antenna elements *: over a multi-beam array antenna 400 constituted of four panels 411, 412, 413 and 414.

. : The four panels are on different respective sides of a cube and thus the multi-beam * antenna is able to cover 360°. Beam patterns of adjacent panels, e.g. panels 411 and 412, may overlap and thus they can advantageously be controlled to point at a single transmitter 435 to increase the gain.

Other arrangements are also possible with three, five or more panels for covering 3600 or a more reduced range of angles. In a particular embodiment, the different groups of antenna elements are all disposed over one and the same flat panel.

There is one group of antenna elements arranged on each panel of the array antenna. Each of the four groups of antenna elements may be similar to one of the groups lOOa, lOOb, lOOc and lOOd in figure 1 and may be controlled according to the flow chart depicted in figure 2.

Considering the arrangement of the antenna as shown in figure 4, the step 320 of calculating the reception angle relatively to a first group of antenna elements, for example those disposed over panel 411, using a known reception angle relatively to a second group of antenna elements, for example those disposed over panel 412, can be performed by adding the angle between the two panels 411 and 412, i.e. 900.

The above calculation is performed under the assumption that the signals are reaching the different antenna elements according parallel lines which is a reasonable assumption considering that the distance between the different panels is rather small compared to the distance between the antenna and the emitting point 435.

For systems where the emitting point is not sufficiently distant from the antenna, the calculation of the reception angle relatively to a given panel based on the reception angle relatively to an adjacent panel may be performed more precisely as explained with regards to figure 5.

Figure 5 shows a coordinate system that helps illustrate the reception of signals by the array antenna of figure 4.

Reception angle of signals relatively to panel 411 is f3 measured relatively to Y axis, and reception angle of signals relatively to panel 412 is e measured relatively to X axis.

The relationship between these two angles can be expressed as follows: * ** (dcos,8+s * O=arctan * *, dsinp -s * S..

where d is the distance from the center of the antenna panel 411 to the emitting point and s is half the width of a panel.

The distance d, if not known in advance, may be determined using equations describing the path loss known in the prior art. For example, the attenuation of the received power is given by the following formula: * * * / * .. PR=PTI---4ird where PR is the received power and PT the transmission power, and A is the wavelength of the carrier used to modulate the transmitted radio signal. This formula reproduce the fact that signal strength does not fade in a linear manner, but inversely as the square of the distance.

The Friis equation gives a complete accounting for all the factors from the transmitting device to the receiving device by including the antennas gains: -10 -where G is the transmitter antenna gain and GA the receiver antenna gain.

It is also possible to determine the delay t between the signals received from the two panels that is to be applied in the delay units 150 as depicted in figure 1 prior their combination. Indeed, we have: -r2 d-((dcos/3+s)/sinO where c is the speed of light.

In an alternate embodiment, a lookup table is maintained in memory that establishes a correspondence between the weighting coefficients associated with the first and the second groups of antenna elements taking into account the relative spatial location between these two groups.

The updating of the weighting coefficients is thus performed by reading in the lookup table the updated weighting coefficients to be associated with the first group of antenna elements.

The physical layer in this example implements a time division multiplexing (TOM) that divides the time domain into a plurality of time slots 610. A time slot is periodically assigned to a given transmitter (for example emitter 435) to send its data. Data is divided :.:.20 into physical data units to fit in the assigned time slots.

Physical data units typically contain a preamble 640, a header 630 and payload data 620. The preamble 640 allows the receiver to synchronize itself with the transmitter. The header 630 contains control information (modulation scheme, transmission rate, length of data unit, etc.) necessary to decode the payload data 620.

Typically, the modulation applied to the signals of the preamble and the header is more robust against errors (Binary Phase Shift Keying (BPSK) for example) than the modulation applied to signals carrying payload data (Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM) for example). This is because the preamble and the header contain sensitive information and are generally smaller in size, whereas the quantity of data contained in the payload is much larger requiring thus more efficient modulation.

In a preferred embodiment of the invention, the adjustment of the reception angles of the array antenna is performed only during the period of time of reception of the preamble and the header. Thus during this time interval at least one group of antenna 11 -elements operates in tracking mode while at least one other group of antenna elements operates in receiving mode. However, during the period of time of reception of the payload data, preferably all the groups of antenna elements operate in receiving mode.

This has the advantage of maintaining an acceptable Level of quality during the reception of the preamble and the header due to the use of the robust modulation even though not all the antenna elements contribute in the received signals gain.

Furthermore, a lot of signal processing is performed to control the modem parameters (e.g. gain and phase of the received radio signals) during the preamble and header reception time. This signal processing includes for example the automatic gain control, synchronization etc. It is thus advantageous to have the number of antenna elements used in receiving mode not varying during the whole period of reception of the preamble and header signals to have the modem parameters tuned appropriately.

On the other hand, during the reception of payload data, the contribution of aH the groups of antenna elements functioning in receiving mode allows to increase the reception gain, and the signal to noise ratio, and consequently reduces the probability of errors after demodulation.

Figure 7 depicts a flow chart illustrating a method of receiving signals in a wireless TOM system according to one embodiment of the invention.

We assume that the multi-beam antenna array is formed by N groups of antenna elements numbered from I to N. A counter value i is initially se to 1 (step 700).

When a first time interval representing the time period of receiving the preamble and the header is detected (step 710), one group (I) of antenna elements operates in tracking S...

mode (step 720) whereas the other groups operate in receiving mode (step 730). If more than one group of antenna elements operate in receiving mode, the received signals are combined (step not shown in figure).

When a second time interval representing the time period of receiving payload data is detected (step 740), all groups of antenna elements operate in receiving mode (step 750). The different received signals are then combined (step 760) according to the * embodiment of the invention as described with regards to figure 1.

When iterating over new first and second time intervals, the group of antenna elements used for tracking is changed, for example using the next group in the sequence of the N groups of antenna elements (step 780).

The advantage of alternating between different groups of antenna elements used for tracking the received signals relates to the fact that some groups of antenna elements may be better positioned relatively to the emitting point than other groups which leads to a more accurate angle determination. Indeed, angle variations are more significant and thus -12-detectable when the emitting point is positioned close to the line perpendicular to a given panel.

Figure 8 is a schematic configuration illustrating the functional blocks for receiving signals through one group of antenna elements according to another embodiment of the invention.

The functional blocks llOa/llOb, 112a/112b and 140 are similar to those described with regards to figure 1. However, in this embodiment one and the same group of antenna elements 1 OOa is controlled by the two beam control unit 11 Oa and 11 Ob in order to produce a first and a second processed signals.

During a tacking period, the set of weighting coefficients in the beam control unit 1 lOb are adjusted so as to track changes, if any, in a direction of arrival of the received radio signal, whilst the set of weighting coefficients in the beam control unit 1 lOa are maintained substantially unchanged.

Following the tracking period, the set of weighting coefficients in the beam control unit 11 Oa are updated in dependence upon the adjusted set of weighting coefficients in the beam control unit IlOb.

As the same group of antenna elements is used in this embodiment for both beani control units llOa and ilOb, the update consists simply in copying the set of weighting coefficients from beam control unit 11 Ob to beam control unit 11 Ga. This can be performed through a read from the weights control unit 115b and write into the weights control unit 115a.

*:e:.* The use of one and the same group of antenna elements has thus the advantage of * .*.

* easily and accurately updating the weighting coefficients.

During a receiving period during which both the two beam control units 11 Ga and * 25 liOb operate in receiving mode, the first and second processed signals are combined *:: before delivering the combined signal to the receiver unit 140. The combination allows to recover the signal power that was split between the two branches of the beam control units 1 lOa/llOb at the output of the group of antenna elements lOOa.

* Another advantage of using one group of antenna elements is that there is no phase difference to cope with before combining the processed signals as there is no spatial disparity between different groups of antenna elements.

Figure 9 illustrates a schematic configuration of a communication device embodying the invention. The communication device is, for example, part of wireless speaker apparatus that further includes one or more speakers.

A RAM 902 functions as a main memory, a work area, etc., of CPU 901, and the memory capacity thereof can be expanded by an optional RAM connected to an expansion port (not illustrated). CPU 901 Is capable of executing instructions on powering up of the communicating apparatus from program ROM 903. After the powering up, CPU 901 is capable of executing instructions from RAM 902 relating to a computer program after those instructions have been loaded from the program ROM 903 or an external memory (not illustrated). Such computer program, when executed by the CPU 901, causes part or all of the steps of the flowcharts shown in figures 2, 3 and 7 to be performed.

Antenna 904 is typically a multi-beam array antenna that can be electronically controlled by code instructions executed by CPU 901 to act as a beamformer according the different embodiments of the invention.

An RF front end 905 receives an RF signal from the antenna 904 to be delivered to the base band unit 806. The base band unit 906 demodulates the signal received from the front-end unit 905. Reference numeral 911 is an inputioutput interface that delivers the received signals to a receiving unit (not shown). * ,S *. . * Se *.* S * S *5**

S

* 5I5S. * * *

** S... * S * S... 0* S

S S S S **

Claims

CLAiMS 1. A receiving method comprising: receiving a radio signal in a tracking period; applying first beamformer processing to the radio signal received in said tracking period, the first beamformer processing comprising obtaining respective antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a first set of weighting coefficients so as to produce a first processed signal corresponding to a first reception beam pattern; applying second beamformer processing to the radio signal received in said tracking period, the second beamformer processing comprising obtaining respective antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a second set of weighting coefficients so as to produce a second processed signal corresponding to a second reception beam pattern; during the tracking period, adjusting the second set of weighting coefficients so as to track changes, if any, in a direction of arrival of the received radio signal, whilst maintaining the first set of weighting coefficients substantially unchanged; 20 following the tracking period, updating the first setof weighting coefficients in dependence upon the adjusted second set of weighting coefficients and applying the first beamformer processing to the radio signal received following the tracking period using the * updated first set of weighting coefficients. * *
2. A receiving method as claimed in claim 1, further comprising applying the : second beamformer processing to the radio signal received following the tracking period * and combining the first and second processed signals.
3. A receiving method as claimed in claim 1 or 2, having a receiving period following said tracking period, the first set of weighting coefficients being updated at or prior to a start of the receiving period and being used for applying the first beamformer processing to the radio signal received over the course of the receiving period.
4. A receiving method as claimed in claim 3, having alternate such tracking and receiving periods.
5. A receiving method as claimed in any preceding claim, wherein in the first beamformer processing the antenna signals are obtained from a first such group of antenna elements and in the second beamformer processing the antenna signals are obtained from a second such group of antenna elements, different from said first group.
6. A receiving method as claimed in claim 5, wherein the first and second groups of antenna elements have different directions and the first set of weighting coefficients are updated in dependence upon the different directions as well as upon the adjusted second set of weighting coefficients.
7. A receiving method as claimed in any one of claims 1 to 4, wherein in both the first beamformer processing and the second beamformer processing the antenna signals are obtained from the same group of antenna elements.
8. A program which, when executed by a computer or a processor in a device, causes the device to carry out a method as claimed in any one of claims 1 to 7.
9. A receiving device comprising: means for receiving a radio signal in a tracking period; means for applying first beamformer processing to the radio signal received in said *.*.. tracking period, the first beamformer processing comprising obtaining respective antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a first set of *..* :25 weighting coefficients so as to produce a first processed signal corresponding to a first ** S. S. * * reception beam pattern; means for applying second beamformer processing to the radio signal received in : said tracking period, the second beamformer processing comprising obtaining respective * antenna signals from a group of antenna elements, each antenna signal representing the received radio signal, and combining the antenna signals in dependence upon a second set of weighting coefficients so as to produce a second processed signal corresponding to a second reception beam pattern; means for adjusting the second set of weighting coefficients during the tracking period so as to track changes, if any, in a direction of arrival of the received radio signal, whilst maintaining the first set of weighting coefficients substantially unchanged; and means operable, following the tracking period, to update the first set of weighting coefficients in dependence upon the adjusted second set of weighting coefficients and to -16-apply the first beamformer processing to the radio signal received following the tracking period using the updated first set of weighting coefficients.
10. Wireless speaker apparatus comprising a receiving device as claimed in claim 9 and at least one speaker. * .. * * * * *. **** * S S...* *05 S. * .SS. S* ** * . S...S S... S. S * . . * I.