TRANSMITTER AND METHOD WITH RF POWER AMPLIFIER HAVING PREDISTORTED BIAS

摘要

A transmitter (32) generates a time-varying stabilized bias signal (82) from which sub-RF distortion signals (26, 29) have been cancelled. The distortion signals (26, 29) are byproducts of imperfect amplification and of biasing networks. An envelope amplifier (84) includes a high bandwidth differential input, linear, bias signal amplifier (120) and a low bandwidth switching amplifier (122) coupled together to achieve both a high bandwidth and high efficiency. A control loop (154) feeds a portion of the voltage V(t) from a conduction node (146) of the RF power amplifier (36) to one of the differential inputs of the linear bias signal amplifier (120), while a bias control signal (92) drives the other differential input. The portion of voltage V(t) fed to bias signal amplifier (120) is a low power portion from which the RF portion has been removed. A bias signal (128) may be predistorted to cancel distortion signals (26, 29).

主权项

1. A method of operating a bias-stabilized RF transmitter comprising:
generating a target bias signal; extracting a magnitude signal from a baseband complex communication signal; forming a derivative with respect to time of said magnitude signal and a delayed function of said magnitude signal; performing at least one mathematical operation upon said delayed function of said magnitude signal and upon said derivative with respect to time of said magnitude signal to produce a bias stabilization signal; applying a predistorted bias signal formed from said target bias signal and said bias stabilization signal to an input of an envelope amplifier; and passing an amplified predistorted bias signal from an output of said envelope amplifier through an RF choke to a conduction channel node of an RF power amplifier, where said amplified predistorted bias signal becomes altered to more closely resemble said target bias signal by a distortion which is a byproduct of amplifying an RF communication signal formed from said baseband complex communication signal.