Non-linear distortion detection method and distortion compensation amplifying device

A distortion compensation amplifying device including:

• a power amplifier which subjects an input signal to power amplification;
• a predistorter which compensates non-linear distortions that appear in the power amplifier, as to an inputted modulation signal to be transmitted;
• an A/D converter which samples a feedback signal of an output of the power amplifier at a specified frequency;
• a distortion detection unit which detects distortion components contained in the power amplifier output, on the basis of the A/D-converted feedback signal, and which outputs the distortion components as distortion values;
• and
• a control unit which controls the predistorter on the basis of the distortion values;
• wherein:
• the A/D converter samples the feedback signal at a frequency capable of sampling a frequency band that contains the modulation signal to be transmitted and that does not contain intermodulation distortions;
• and
• the distortion detection unit includes:
• a plurality of averaging portions that average an output from an equalizer, at respective levels of an amplitude of a reference symbol, and that output the average values as the distortion values corresponding to the levels of the amplitude of the reference symbol;
• and
• the equalizer that receives an input signal to the predistorter, as the reference symbol, that equalizes the feedback signal of the power amplifier output by a FIR filter, that calculates an equalization error between the equalized signal and the reference symbol, that divides a calculated result of a complex conjugate calculation between the equalization error and the reference symbol, by a square of an amplitude component of the reference symbol and decides the level of the amplitude of the reference symbol on the basis of the square of the amplitude component of the reference symbol, and that outputs a result of the division to the averaging portion corresponding to the decided level of the amplitude.

A distortion compensation amplifying device including:

• a power amplifier which subjects an input signal to power amplification;
• a predistorter which compensates non-linear distortions that appear in the power amplifier, as to an inputted modulation signal to be transmitted;
• an A/D converter which samples a feedback signal of an output of the power amplifier at a specified frequency;
• a distortion detection unit which detects distortion components contained in the power amplifier output, on the basis of the A/D-converted feedback signal, and which outputs the distortion components as distortion values;
• and
• a control unit which controls the predistorter on the basis of the distortion values;
• wherein:
• the distortion detection unit includes an equalizer that receives the input signal to the predistorter, as a reference symbol, that equalizes the feedback signal of the power amplifier output by a FIR filter, and that outputs an equalization error between the equalized signal and the reference symbol, as the distortion value;
• the predistorter includes a third-order intermodulation distortion generator, a fifth-order intermodulation distortion generator, a seventh-order intermodulation distortion generator, a first FIR filter corresponding to the third-order intermodulation distortion generator, a second FIR filter corresponding to the fifth-order intermodulation distortion generator, and a third FIR filter corresponding to the seventh-order intermodulation distortion generator;
• and
• the control unit updates tap coefficients of the first, second and third FIR filters of the predistorter on the basis of the distortion values outputted from the distortion detection unit.

A distortion compensation amplifying device including:

• a power amplifier which subjects an input signal to power amplification;
• a predistorter which compensates non-linear distortions that appear in the power amplifier, as to an inputted modulation signal to be transmitted;
• an A/D converter which samples a feedback signal of an output of the power amplifier at a specified frequency;
• a distortion detection unit which detects distortion components contained in the power amplifier output, on the basis of the A/D-converted feedback signal, and which outputs the distortion components as distortion values;
• and
• a control unit which controls the predistorter on the basis of the distortion values;
• wherein:
• the A/D converter samples the feedback signal at a frequency capable of sampling a frequency band that contains the modulation signal to be transmitted and that does not contain intermodulation distortions;
• the distortion detection unit includes an equalizer that receives an input signal to the predistorter, as a reference symbol, that equalizes the feedback signal of the power amplifier output by a FIR filter and that outputs an equalization error between the equalized signal and the reference symbol, and an absolute-value averaging portion that outputs as the distortion value, a temporal average value obtained by temporally averaging absolute values of the equalization error over a specified time period;
• the distortion detection unit includes an LMS portion that updates a tap coefficient of the FIR filter in conformity with an LMS algorithm;
• and
• the LMS portion updates the tap coefficient with reference to the reference symbol every plurality of sample time periods.