Distortion compensation apparatus and distortion compensation method

A distortion compensation apparatus configured to compensate for non-linear distortion of a power amplifier, the distortion compensation apparatus comprising:

• an AD converter configured to feed back and analog/digital (AD) convert an output signal of the power amplifier and output the AD converted signal as a feedback signal;
• a digital predistorter configured to perform distortion compensation processing on an input signal by using the feedback signal and output the signal undergoing distortion compensation processing;
• and
• a DA converter configured to be provided between the digital predistorter and the power amplifier, digital/analog (DA) convert an output signal of the digital predistorter, and output the DA converted signal to the power amplifier,
• wherein the digital predistorter
• operates at a sampling rate for sampling the input signal not upsampled in a previous stage of the digital predistorter,
• includes:
• a polynomial structure configured to include a pseudo-interpolation/sub-sample-shift processor configured to pseudo-interpolate a first sample point between sample points of the input signal and shift the pseudo-interpolated first sample point by a sub-sample and include a multiplexer configured to select a combination of a sub-sample shift amount in complex-multiplication of a signal acquired by processing the input signal by the pseudo-interpolation/sub-sample-shift processor by an output of a look up table related to an amplitude address corresponding to an amplitude of the signal acquired by processing the input signal by the pseudo-interpolation/sub-sample-shift processor;
• and
• a finite impulse response (FIR) filter configured to be provided in a subsequent stage of the polynomial structure and include a sub-sample delay filter delaying a second sample point of the input signal by a sub-sample, and
• compensates for distortion due to a third sample point of the input signal and compensates for distortion due to the first sub-sample point between the sample points of the input signal, by using the polynomial structure and the FIR filter.