Radio communication device and distortion compensation method

1. A radio communication device comprising:

a plurality of antenna elements;

a phase shifter that applies weights for each of the antenna elements respectively to first-band data and second-band data of different frequency bands to form beams corresponding to the first-band data and the second-band data;

a power amplifier that is arranged for each of the antenna elements and that amplifies the first-band data and the second-band data; and

a processor configured to compensate for non-linear distortion that occurs in the first-band data and the second-band data in the power amplifier,

wherein the processor executes a process including

calculating, using a first distortion compensation coefficient, a distortion compensation signal that compensates for in-band non-linear distortion of the first-band data and the second-band data from the first-band data and the second-band data, and

calculating, using a second distortion compensation coefficient, an out-of-band compensation signal that compensates for out-of-band non-linear distortion of the first-band data and the second-band data from the first-band data and the second-band data, and

the power amplifier amplifies a signal obtained by synthesizing the distortion compensation signal and the out-of-band compensation signal.

2. The radio communication device according to claim 1 , wherein the processor executes the process further including updating the first distortion compensation coefficient and the second distortion compensation coefficient based on a feedback signal that is fed back from the power amplifier, the first-band data, and the second-band data.

3. The radio communication device according to claim 2 , wherein the updating includes

performing phase conversion same as phase conversion by the phase shifter on the first-band data and the second-band data,

calculating an error between a reference signal obtained by the phase conversion and the feedback signal,

updating a base coefficient such that the calculated error becomes smaller, and

calculating, based on the updated base coefficient, the first distortion compensation coefficient and the second distortion compensation coefficient.

4. The radio communication device according to claim 2 , further comprising a switch that switches between signals that are output from the power amplifiers of the respective antenna elements at given intervals and feedbacks the signals to the processor.

5. The radio communication device according to claim 1 , further comprising an out-of-band phase shifter that applies, to the out-of-band compensation signal, an out-of-band weight corresponding to a weight that is applied by the phase shifter to the distortion compensation signal.

6. The radio communication device according to claim 1 , wherein the calculating the out-of-band compensation signal includes calculating the out-of-band compensation signal that compensates for out-of-band third order distortion of the first-band data and the second-band data.

7. A distortion compensation method that is executed by a radio communication device including a plurality of antenna elements; a phase shifter that applies weights for each of the antenna elements respectively to first-band data and second-band data of different frequency bands to form beams corresponding to the first-band data and the second-band data; and a power amplifier that is arranged for each of the antenna elements and that amplifies the first-band data and the second-band data, the method comprising:

calculating, using a first distortion compensation coefficient, a distortion compensation signal that compensates for in-band non-linear distortion of the first-band data and the second-band data from the first-band data and the second-band data;

calculating, using a second distortion compensation coefficient, an out-of-band compensation signal that compensates for out-of-band non-linear distortion of the first-band data and the second-band data from the first-band data and the second-band data;

synthesizing the distortion compensation signal and the out-of-band compensation signal; and

amplifying, using the power amplifier of each of the antenna elements, a signal obtained by the synthesizing.