Feed forward amplifiers and methods

摘要

Feed forward amplifiers and methods particularly suited for power multichannel microwave amplifiers for cellular phone base stations and the like. The input signal is modulated with a small percentage of modulation at a relatively low frequency before being amplified by the main amplifier. At the same time, the input signal is also coupled to provide inphase and quadrature components thereof to be mixed with the amplifier output and lowpass filtered to extract a component of the low frequency responsive to modulation components in the amplifier output due to the low frequency modulation. This signal is then multiplied by the low frequency to provide a DC voltage controlling an adaptive control circuit to adjust the inphase and quadrature components of the intermodulation components and the low frequency modulation of the entire signal so that the result can be combined with the main amplified signal to remove the intermodulation components and the low frequency modulation of the entire signal from the amplifier output.