Distortion reduction
AssigneeAndrew Corporation
InventorPeter Kenington
Life of this patent
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Abstract
The input signal (110) to a non-linear amplifier (112) is predistorted by injecting a correction signal at coupler (124). To generate the correction signal, a sample of the input signal is amplified using amplifier (130) which has substantially the same distortion generating characteristics as amplifier (112). The output of amplifier (130) is sampled, and the main tone energy is removed at (138), leaving the correction signal for injection to the main signal path. The main portion of the output of amplifier (130) is added coherently to the output of amplifier (112) to enhance efficiency. The correction signal can be manipulated to correct distortion in the output of combiner (152) due to the main portion of the output of amplifier (130).
Claims13
Apparatus for reducing the distortion appearing in an amplified output signal, the apparatus comprising:
- a first sampler adapted to sample, as a sample signal, a portion of the input signal destined for amplification by a first amplifier;
- a second amplifier adapted to amplify the sample signal to produce an amplified sample signal, the distortion characteristics of the second amplifier being at least similar to those of the first amplifier;
- an extractor adapted to extract a distortion signal from the amplified sample signal;
- a first combiner adapted to combine the distortion signal with the input signal destined for amplification by the first amplifier to reduce distortion of the output of the first amplifier;
- and
- a second combiner adapted to combine the outputs of the first and second amplifiers to produce the amplified output signal;
- wherein the extractor comprises a second sampler adapted to sample the amplified sample signal and a suppressor adapted to remove the amplified input signal appearing in the sample of the amplified sample signal.
A method of reducing the distortion appearing in an amplified output signal, the method comprising the steps of:
- first sampling, as a sample signal, a portion of an input signal destined for amplification by a first amplification process;
- amplifying the sample signal using a second amplification process, whose distortion characteristics are at least similar to those of the first amplification process, to produce an amplified sample signal;
- extracting a distortion signal from the amplified sample signal;
- first combining the distortion signal with the input signal destined for amplification by the first amplification process to reduce distortion of the output of the first amplification process;
- and
- second combining the outputs of the first and second amplification processes to produce the amplified output signal;
- wherein the step of extracting a distortion signal comprises the steps of second sampling the amplified sample signal and removing the amplified input signal appearing in the sample of the amplified sample signal.
Dependencies are inferred from the claim text.