Patent ID: 6392483
Filing Date: 2002-05-21
Classification: H03F

Abstract:
A feed-forward amplifier for amplifying a power of an input transmission signal and including a distortion detecting loop for detecting a distortion component and a distortion canceling loop cascade-connected to said distortion detecting loop for canceling said distortion component, wherein:said distortion detecting loop comprises: a main amplifier path containing a main amplifier; a signal power dynamic range compressing circuit inserted in said main amplifier path at an input side of said main amplifier, for compressing a power dynamic range of said input transmission signal; a first linear signal transfer path; a first directional coupler for distributing said input transmission signal to said main amplifier path and said first linear signal transfer path; and a second directional coupler for power-combining output signals from said main amplifier path and said first linear signal transfer path and for dividing said combined output signal into first and second combined outputs, said distortion canceling loop comprises: a second linear signal transfer path supplied with the first combined output from said second directional coupler, for transferring said supplied first combined output; an auxiliary amplifier path containing an auxiliary amplifier and supplied with the second combined output from said second directional coupler, for transferring said supplied second combined output; and a third directional coupler for power-combining outputs from said second linear signal transfer path and said auxiliary amplifier path and for outputting said power-combined transmission signal, and said signal power dynamic range compressing circuit comprises: a fourth directional coupler for dividing a signal on said main amplifier path into first and second signals and for outputting said first and second divided signals; a third linear signal transfer path for linearly transferring the first divided signal from said fourth directional coupler; a compressing signal generator for generating a compressing signal that makes an envelope of said first divided signal constant based on the second divided signal from said fourth directional coupler; and a fifth directional coupler for power-combining an output signal from said third linear signal transfer path and said compressing signal from said compressing signal generator and for providing said power-combined output to said main amplifier.