Wireless communication device and distortion compensation method

1. A wireless communication device comprising:

a plurality of power amplifiers provided for a plurality of respective antenna elements, each of the power amplifiers amplifying a signal;

a distortion compensation unit that executes distortion compensation of a transmission signal by using an inverse function corresponding to nonlinear distortion generated in the power amplifiers; and

a controller that operates by switching a first mode and a second mode, the first mode setting individual inverse functions for the respective power amplifiers in the distortion compensation unit and updating coefficients of the individual inverse functions, the second mode suspending the update of the coefficients of the individual inverse functions and setting, in the distortion compensation unit, an integrated inverse function acquired by performing weighted addition of the individual inverse functions.

2. The wireless communication device according to claim 1 , further comprising a feedback unit that feeds back a signal output from one of the power amplifiers to the controller, when the controller operates in the first mode.

3. The wireless communication device according to claim 1 , wherein, in the first mode, the controller updates the coefficients of the individual inverse functions for the respective power amplifiers, for a predetermined time each.

4. The wireless communication device according to claim 1 , wherein, in the first mode, the controller shifts to the second mode when the update of the coefficients of the individual inverse functions regarding all of the power amplifiers is completed.

5. The wireless communication device according to claim 1 , wherein, in the second mode, the controller calculates weights of the respective power amplifiers in accordance with gains of the respective power amplifiers, and performs weighted addition of the individual inverse functions of the respective power amplifiers using the calculated weights to derive the integrated inverse function.

6. The wireless communication device according to claim 5 , wherein the controller calculates the weights of the respective power amplifiers to make a sum of the weights of the power amplifiers “1”.

7. A distortion compensation method executed by a wireless communication device including: a plurality of power amplifiers provided for a plurality of respective antenna elements, each of the power amplifiers amplifying a signal; and a distortion compensation unit that executes distortion compensation of a transmission signal by using an inverse function corresponding to nonlinear distortion generated in the power amplifiers, the distortion compensation method comprising:

operating in a first mode that sets individual inverse functions for the respective power amplifiers in the distortion compensation unit, and updates coefficients of the individual inverse functions; and

operating in a second mode that suspends the update of the coefficients of the individual inverse functions and sets, in the distortion compensation unit, an integrated inverse function acquired by performing weighted addition of the individual inverse functions.