Patent ID: 7170342
Filing Date: 2007-01-30
Classification: H03F

Abstract:
1. A linear power amplifier comprising: a digital predistorter supplied with a digital transmission signal, for predistorting said digital transmission signal by use of a power series model to generate a predistorted signal; a DA converter for converting said predistorted signal from said digital predistorter into an analog predistorted signal; a frequency upconverting part for upconverting said analog predistorted signal to a transmit frequency band; a power amplifier for power-amplifying said upconverted signal; a frequency downconverting part for downconverting a portion of the output from said power amplifier to output a downconverted signal; and a digital predistorter control part for extracting distortion components of the same odd orders as those of said power series model and for controlling coefficients of said digital predistorter in a manner to lower the levels of said odd-order distortion components, wherein said digital predistorter includes distortion generating paths each containing a series connection of a distortion generator for generating one of distortions based on said power series model and a frequency characteristic compensator, and an adder for adding odd-order distortions from said distortion generating paths to said digital transmission signal and for outputting a combined output as said predistorted signal, said digital predistorter control part includes means for controlling frequency characteristics of said frequency characteristic compensators based on said extracted odd-order distortion components, and said frequency characteristic compensators are formed by FIR filters whose frequency characteristics are controlled by said extracted odd-order components.