Patent ID: 6320461
Filing Date: 2001-11-20
Classification: H03F

Abstract:
An adaptively controlled feedforward amplifier system that reduces distortion generated by a power amplifier, comprising:means for generating a plurality of pilot signals with modulation that enhances detectability of components of the pilot signals;a main amplifier that receives an amplifier input signal in combination with the plurality of pilot signal components and that outputs an amplified output signal having the pilot signals components;means for extracting the input signal from the pilot signal components and delaying the extracted input signal;means for producing an error signal by subtracting the delayed extracted input signal from the main amplifier output signal, said error signal including the pilot signal components and amplifier harmonic and intermodulation distortion signal components;an error amplifier that receives the error signal as an input signal and that produces an amplified error signal having the pilot signal components as an output signal;means for subtracting the amplified error signal from the main amplifier output signal to produce a final output signal that has no distortion components;an adaptive control circuit that continually adjusts amplitudes and phases of the main amplifier and error amplifier input signals,wherein said adaptive control circuit comprises:means for sampling a portion of the extracted input signal for use as a reference signal;means for sampling a portion of the error signal, which is the difference between the main amplifier output signal and the delayed input signal;a synchronous detector that, utilizing the sampled portion of the extracted input signal and the sampled portion of the error signal, detects voltages representing quadrature components of a residual portion of the input signal in the error signal; anda vector controller that utilizes the voltages detected by said synchronous detector to automatically adjust the amplitude and phase of the input signal until the residual portion of the input signal in the error signal is reduced to a desired level.