Switched beam antenna with digitally controlled weighted radio frequency combining
A wireless communication system, wherein a sub-set of radio frequency signals received from corresponding antenna elements is selected and combined into a single radio frequency signal, the single radio frequency signal being processed and demodulated in a single processing chain, includes a radio frequency phasing network for co-phasing the selected radio frequency signals before combining and a processor for controlling combining and phasing in order to obtain a single radio frequency signal having a radio performance indicator which satisfies predetermined conditions.
1. A wireless communication system comprising:
a plurality of antenna elements;
a selector for selecting a sub-set of received radio frequency signals from said antenna elements;
a combiner for combining said sub-set of received radio frequency signals into a single radio frequency signal;
a processing chain for processing and demodulating said single radio frequency signal and for generating at least a radio performance indicator representative of the quality of said single radio frequency signal;
a processor detecting said radio performance indicator for generating a selection signal(s) for said selector and a phase shift signal for said radio frequency phasing network in order to obtain a single radio frequency signal having a radio performance indicator within a predetermined range; and
a radio frequency phasing network for co-phasing said selected radio frequency signals before combining in said combiner by applying a phase shift to at least one signal in said sub-set.
2. The system according to claim 1 , wherein said selector selects two received radio signals.
3. The system according to claim 2 , wherein said radio frequency phasing network applies a phase shift to said two selected radio frequency signals.
4. The system according to claim 2 , wherein said phase shift signal and said selection signal(s) are used, in transmission, for phasing at least two signals to be transmitted and for selecting at least two antenna elements, respectively.
5. The system according to claim 4 , wherein two signals to be transmitted are obtained by splitting a single signal into two separate signals with a same power level.
6. The system according to claim 1 , wherein said radio performance indicator is an indicator selected from the following group or a combination thereof:
received signal strength indicator,
the throughput, and
the packet error rate.
7. The system according to claim 6 , wherein a selection signal(s) and a phase shift signal are generated in order to maximize the received signal strength indicator or the throughput or a combination of them.
8. The system according to claim 6 , wherein a selection signal(s) and a phase shift signal are generated in order to minimize the packet error rate of said single radio frequency signal.
9. The system according to claim 1 , wherein said phase shift is applied by multiplying a signal by a complex-valued weight having unitary modulus.
10. The system according to claim 9 , wherein said phase shift is applied in quantized form.
11. The system according to claim 10 , wherein said phase shift is applied by means of a plurality of delay lines selectively switched.
12. A method of processing a radio frequency signal in a radio communication system, said signal being received by a plurality of antenna elements, comprising the steps of:
selecting a sub-set of received radio frequency signals from said antenna elements;
combining said sub-set of received radio frequency signals into a single radio frequency signal;
processing and demodulating said single radio frequency signal for generating at least a radio performance indicator representative of the quality of said single radio frequency signal;
subjecting signals in said sub-set of received radio frequency signals to co-phasing, by applying a phase shift to at least one signal in said sub-set;
detecting said radio performance indicator; and
selecting a combination of sub-set of received radio frequency signals and a phase shift for said co-phasing step, in order to obtain a single radio frequency signal having a radio performance indicator within a predetermined range.
13. The method according to claim 12 , wherein said selecting a combination comprises selecting two received radio frequency signals.
14. The method according to claim 13 , wherein said co-phasing comprises applying a phase shift to said two selected radio frequency signals.
15. A method according to claim 13 , wherein said selecting a combination comprises:
subsequently selecting pairs of received radio frequency signals and, for each pair, measuring said radio performance indicator;
selecting two pairs of signals providing higher radio performance indicator values;
subjecting the six possible different combination pairs of the four signals in said two pairs to different phase shifts;
measuring for each combination pair and for each phase shift said radio performance indicator in order to obtain a single pair of received radio frequency signals corresponding to a higher value of said radio performance indicator.
16. The method according to claim 15 , wherein in said step of selecting the two pairs of signals providing higher radio performance indicator values, no phase shift is applied to said pairs of signals.
17. The method according to claim 12 , wherein said radio performance indicator is an indicator selected from the following group or a combination thereof:
received signal strength indicator,
the throughput, and
the packet error rate.
18. The method according to claim 17 , wherein said combination of sub-set of received radio frequency signals and phase shift for said co-phasing step is selected in order to maximize the received signal strength indicator or the throughput or a combination of them.
19. The method according to claim 17 , wherein said combination of sub-set of received radio frequency signals and phase shift for said co-phasing step is selected in order to minimize the packet error rate of said single radio frequency signal.
20. The method according to claim 12 , wherein said phase shift is applied by multiplying a signal by a complex-valued weight having unitary modulus.
21. The method according to claim 20 , wherein said phase shift is applied in quantized form.
22. The method according to claim 12 , wherein said combination of sub-set of received radio frequency signals and phase shift for said co-phasing step are used, in transmission, for phasing at least two signals to be transmitted and for selecting at least two antenna elements, respectively.
23. The method according to claim 22 , wherein two signals to be transmitted are obtained by splitting a single signal into two separate signals with the same power level.
24. A wireless local area network device comprising a wireless communication system according to claim 1 .