Signal processing device and inter-beam interference suppression method

1. A signal processing device comprising:

a first subarray that includes a plurality of power amplifiers and a plurality of phase shifters that are associated with a plurality of antenna elements, respectively, and that forms a first beam facing in a first direction;

a second subarray that includes a plurality of power amplifiers and a plurality of phase shifters that are associated with a plurality of antenna elements, respectively, and that forms a second beam facing in a second direction that is different from the first direction;

a feedback unit that feeds back at least signals that are output from the plurality of power amplifiers included in the first subarray; and

a processor that is connected to the first subarray and the second subarray and that outputs a transmission signal to the first subarray and the second subarray, wherein the processor executes a process comprising:

generating, based on a first feedback signal that is fed back by the feedback unit and the transmission signal that is output to the first subarray, a cancellation signal corresponding to an interference component that is applied to the second beam by the first beam; and

adding the generated cancellation signal to the transmission signal that is output to the second subarray.

2. The signal processing device according to claim 1 , wherein the feedback unit acquires the first feedback signal by extracting a signal component facing in the second direction from the signals that are output from the plurality of power amplifiers included in the first subarray and feeds back the first feedback signal to the processor.

3. The signal processing device according to claim 1 , wherein the feedback unit includes a plurality of phase shifters to each of which a weight that is inverse of a weight set to each of the plurality of phase shifters included in the second subarray is set and each of which shifts a phase of each of the signals that are output from the plurality of power amplifiers included in the first subarray.

4. The signal processing device according to claim 1 , wherein

the feedback unit acquires a second feedback signal by extracting a signal component facing in the first direction from the signals that are output from the plurality of power amplifiers included in the second subarray and feeds back the second feedback signal to the processor, and wherein the processor further executes a process comprising:

generating, based on the second feedback signal that is fed back by the feedback unit and the transmission signal that is output to the second subarray, a cancellation signal corresponding to an interference component that is applied to the first beam by the second beam; and

adding the generated cancellation signal corresponding to the interference component that is applied to the first beam by the second beam to the transmission signal that is output to the first subarray.

5. The signal processing device according to claim 1 , wherein the generating includes

calculating, based on the first feedback signal that is fed back by the feedback unit and the transmission signal that is output to the first subarray, a nonlinear model that indicates a relationship between the transmission signal and the first feedback signal, and

generating the cancellation signal by applying the calculated nonlinear model to the transmission signal that is output to the first subarray.

6. The signal processing device according to claim 1 , wherein the generating includes

calculating, based on the first feedback signal that is fed back by the feedback unit and the transmission signal that is output to the first subarray, a linear model that indicates a relationship between the transmission signal and the first feedback signal, and

generating the cancellation signal by applying the calculated linear model to the transmission signal that is output to the first subarray.

7. The signal processing device according to claim 1 , wherein the adding includes

converting a frequency of the generated cancellation signal to a same frequency as a frequency of the transmission signal that is output to the second subarray, and

adding the cancellation signal after frequency conversion to the transmission signal that is output to the second subarray.

8. The signal processing device according to claim 1 , wherein the adding includes

limiting a frequency band of the generated cancellation signal to a same frequency band as a frequency band of the transmission signal that is output to the second subarray, and

adding the cancellation signal after band limitation to the transmission signal that is output to the second subarray.

9. The signal processing device according to claim 1 , wherein the processor further executes a process comprising compensating, by using a distortion compensation coefficient, nonlinear distortion that occurs in the plurality of power amplifiers included in the first subarray, and wherein

the feedback unit feeds back, in a time-division manner, the first feedback signal that is used to generate the cancellation signal and another feedback signal that is used to update the distortion compensation coefficient.

10. An inter-beam interference suppression method for performing a process in a signal processing device that includes

a first subarray that includes a plurality of power amplifiers and a plurality of phase shifters that are associated with a plurality of antenna elements, respectively, and that forms a first beam facing in a first direction, and

a second subarray that includes a plurality of power amplifiers and a plurality of phase shifters that are associated with a plurality of antenna elements, respectively, and that forms a second beam facing in a second direction that is different from the first direction, the inter-beam interference suppression method comprising:

feeding back at least signals that are output from the plurality of power amplifiers included in the first subarray;

generating, based on a first feedback signal that is fed back and a transmission signal that is transmitted from the first subarray, a cancellation signal corresponding to an interference component that is applied to the second beam by the first beam; and

adding the generated cancellation signal to a transmission signal that is transmitted from the second subarray.

11. The inter-beam interference suppression method according to claim 10 , wherein the feeding back includes acquiring the first feedback signal by extracting a signal component facing in the second direction from the signals that are output from the plurality of power amplifiers included in the first subarray and feeding back the first feedback signal.

12. The inter-beam interference suppression method according to claim 10 , further comprising:

acquiring a second feedback signal by extracting a signal component facing in the first direction from the signals that are output from the plurality of power amplifiers included in the second subarray and feeding back the second feedback signal;

generating, based on the second feedback signal that is fed back and the transmission signal that is transmitted from the second subarray, a cancellation signal corresponding to an interference component that is applied to the first beam by the second beam; and

adding the generated cancellation signal corresponding to the interference component that is applied to the first beam by the second beam to the transmission signal that is transmitted from the first subarray.

13. The inter-beam interference suppression method according to claim 10 , wherein the generating includes

calculating, based on the first feedback signal that is fed back and the transmission signal that is transmitted from the first subarray, a nonlinear model that indicates a relationship between the transmission signal and the first feedback signal, and

generating the cancellation signal by applying the calculated nonlinear model to the transmission signal that is transmitted from the first subarray.

14. The inter-beam interference suppression method according to claim 10 , wherein the generating includes

calculating, based on the first feedback signal that is fed back and the transmission signal that is transmitted from the first subarray, a linear model that indicates a relationship between the transmission signal and the first feedback signal, and

generating the cancellation signal by applying the calculated linear model to the transmission signal that is transmitted from the first subarray.