Feed-forward amplifier
AssigneeNtt Docomo, Inc.
InventorsYasunori Suzuki, Toshio Nojima
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Abstract
In a feed-forward amplifier a signal power dynamic range compressing circuit for compressing the power dynamic range of the input signal to the feed-forward amplifier is provided in a distortion detecting loop at the input side of a main amplifier, and the output backoff of the main amplifier is reduced to thereby achieve high-efficiency amplification of the feed-forward amplifier.
Claims23
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.
A power amplifying method for power-amplifying an input transmission signal by a feed-forward amplifier provided with 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, said method comprising the steps of:
- (a) distributing said input transmission signal to a first linear signal transfer path and a main amplifier path;
- (b) distributing said input transmission signal, distributed to said main amplifier, to a second linear signal transfer path and a compressing signal generating path;
- (c) generating, based on said input transmission signal distributed to said compressing signal generating path, a compressing signal for making a constant-envelope said signal distributed to said second linear signal transfer path;
- (d) power-combining said compressing signal and an output from said second linear signal transfer path and power-amplifying said combined signal by a main amplifier of said main amplifier path;
- (e) power-combining an output from said main amplifier path and an output from said first linear signal transfer path and distributing said power-combined signal to a third linear signal transfer path and an auxiliary amplifier path;
- and
- (f) power-combining an output from said auxiliary amplifier path and an output from said third linear signal transfer path to cancel a distortion component of said input transmission signal transferred over said third linear signal transfer path and outputting said input transmission signal amplified in power.
Dependencies are inferred from the claim text.