Transmission signal power control apparatus, communication apparatus and predistortion coefficient updating method

摘要

A transmission signal power control apparatus includes a power amplifier model unit which generates a learning digital signal by multiplying part of a predistortion signal by model coefficients which tentatively represent the input-output characteristics of a power amplifier, and an adaptive low-pass filter which generates a pseudo feedback signal by attenuating the high frequency components of the learning digital signal by multiplying the learning digital signal by weighting coefficients. Then, the power amplifier model unit updates the model coefficients such that the error between the feedback signal whose the high frequency components are attenuated by the low-pass filter and which is digitized, and the pseudo feedback signal is minimized, and the adaptive low-pass filter updates the weighting coefficients such that the error is minimized.

主权项

1. A transmission signal power control apparatus comprising:
a power amplifier which amplifies a transmission signal; a first low-pass filter which attenuates a frequency component of a feedback signal, which is higher than a certain sampling frequency, the feedback signal being part of a signal that is output from the power amplifier; an analog-to-digital converter which digitizes the feedback signal output from the first low-pass filter by the certain sampling frequency; a predistortion unit which generates a predistortion signal to input to the power amplifier, by multiplying the transmission signal by predistortion coefficients which represent an inverse characteristic of an input-output characteristic of the power amplifier; a power amplifier model unit which generates a learning digital signal by multiplying part of the predistortion signal by model coefficients which tentatively represent the input-output characteristic of the power amplifier; an inverse unit which calculates the predistortion coefficients from the model coefficients; a second low-pass filter which generates a pseudo feedback signal by attenuating a high frequency component of the learning digital signal by multiplying the learning digital signal by weighting coefficients; and a subtractor which calculates an error between the pseudo feedback signal and the digitized feedback signal, wherein the power amplifier model unit updates the model coefficients such that the error is minimized, and the second low-pass filter is an adaptive filter which updates the weighting coefficients such that the error is minimized.