Distortion-compensating power amplifier and method for compensating for distortion to amplify power

1. A distortion-compensating power amplifier comprising:

a power amplifier;

a predistorter that performs pre-distortion processing, the pre-distortion processing applying an inverse characteristic of a distortion characteristic that is generated in the power amplifier to an input signal in a first channel;

a filter that performs band limitation on the pre-distorted input signal by using a frequency characteristic that is shifted to one of a second channel which is a lower frequency band adjacent to the first channel and a third channel which is a higher frequency band adjacent to the first channel with respect to a center frequency of the first channel, the filter having a filter coefficient that is a complex number;

a down-sampler that down-samples the band-limited input signal; and

a digital-to-analog converter that converts the down-sampled input signal from a digital signal to an analog signal.

2. The distortion-compensating power amplifier according to claim 1 , comprising:

an up-sampler that up-samples the input signal that is input thereto,

wherein the predistorter performs the pre-distortion processing on the up-sampled input signal, and

the digital-to-analog converter has a sampling rate that is lower than or equal to determined times of a bandwidth of the input signal that is input to the up-sampler.

3. The distortion-compensating power amplifier according to claim 1 ,

wherein the filter varies the filter coefficient to perform the band limitation.

4. The distortion-compensating power amplifier according to claim 2 ,

wherein the filter varies the filter coefficient by inverting a polarity of an imaginary part of the filter coefficient.

5. The distortion-compensating power amplifier according to claim 2 ,

wherein the filter varies the filter coefficient, based on reception power of a signal in one of the second channel and the third channel.

6. The distortion-compensating power amplifier according to claim 2 ,

wherein the filter varies the filter coefficient, based on a number of terminals that perform communication by using one of the second channel and the third channel.

7. A method for compensating for nonlinear distortion, the method comprising:

performing pre-distortion processing, the pre-distortion processing applying an inverse characteristic of a distortion characteristic that is generated in a power amplifier to an input signal in a first channel;

performing filter processing for performing band limitation on the pre-distorted input signal by using a frequency characteristic that is shifted to one of a second channel which is a lower frequency band adjacent to the first channel and a third channel which is a higher frequency band adjacent to the first channel with respect to a center frequency of the first channel, the filter processing using a filter coefficient that is a complex number;

performing down-sampling on the band-limited input signal; and

converting the down-sampled input signal from a digital signal to an analog signal.

8. The distortion-compensating power amplifier according to claim 1 , comprising a frequency converter that up converts the converted analog signal output from the digital-to-analog converter from a baseband to a carrier frequency.

9. The method for compensating for nonlinear distortion according to claim 7 , comprising up converting the converted analog signal from a baseband to a carrier frequency.

10. The method for compensating for nonlinear distortion according to claim 7 , comprising up sampling the input signal, the pre-distortion processing being performed on the up sampled signal and the converting utilizes a sampling rate that is lower than or equal to the term and times of a bandwidth of the input signal that is up sampled.

11. The method for compensating for nonlinear distortion according to claim 7 , wherein the filter processing varies the filter coefficient to perform the band limitation.

12. The method for compensating for nonlinear distortion according to claim 11 , wherein the filter processing varies the filter coefficient by inverting a polarity of an imaginary part of the filter coefficient.

13. The method for compensating for nonlinear distortion according to claim 11 , wherein the filter processing varies the filter coefficient, based on reception power of a signal in one of the second channel and the third channel.

14. The method for compensating for nonlinear distortion according to claim 11 , wherein the filter processing varies the filter coefficient, based on a number of terminals that perform communication by using one of the second channel and the third channel.