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Abstract

A distortion reduction system uses upstream signal information, such as the carrier frequencies in an input signal, to adjust at least one frequency for a pilot signal to be injected into the distortion reduction system and to be detected at the output of the distortion reduction system, thereby enabling improved distortion reduction of changing input signals. For example, processing circuitry obtains the traffic frequencies making up a signal to be amplified by a feed forward arrangement. Using the traffic frequencies, the processing circuitry determines at least one frequency for a pilot signal, and the processing circuitry tunes a pilot signal generator to the at least one frequency for the pilot signal. The feed forward arrangement receives the signal to be amplified and provides replicas of the signal on a main signal path and on a feed forward path. The pilot signal is injected into the main signal path at the at least one frequency along with the signal to be amplified. The signal and the pilot signal are amplified by an amplifier on the main signal path, resulting in the amplified signal, the amplified pilot signal and distortion signals produced by the amplifier. A replica of the output of the amplifier is placed on a coupling path and combined with a delayed version of the signal on the feed forward path to isolate a replica of the pilot signal and distortion on the feed forward path. The pilot signal and distortion on the feed forward path are combined with the amplified signal, the amplified pilot and the distortion on the main signal path. A sample of the output is provided to pilot detection circuitry which is tuned by the processing circuitry to detect the pilot signal at the at least one frequency. Depending on the amplitude of the pilot signal at the output, the processing circuitry provides gain and/or phase control signal(s) to adjust the relative phase and/or gain between the combining pilot signals to reduce the amplitude of the pilot signal at the output and thereby to reduce the amplitude of the distortion.

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First Claim