Patent ID: 6133791
Filing Date: 2000-10-17
Classification: H03F

Abstract:
A feedforward amplifier comprising:a distortion detector that includes a main amplifier signal path containing a main amplifier, and a first linear signal path containing a first delay circuit and a directional coupler, coupled to an output of said first delay circuit;a distortion eliminator that includes a main amplifier output path containing a second delay circuit, and a distortion injection path containing a first variable attenuator, first variable phase shifter and a sub-amplifier, and that cancels out nonlinear distortion components, which are generated by said main amplifier and detected by said distortion detector, by injecting into an output of said main amplifier an output of said sub-amplifier which amplifies the nonlinear distortion components;an error power extractor for extracting output error power due to variations in said distortion eliminator by combining in opposite phases an output signal of said distortion eliminator with a signal from said first linear signal path in said distortion detector;a first level detector for detecting the output error power extracted by said error power extractor;a first controller for controlling said first variable attenuator and said first variable phase shifter in said distortion eliminator such that the output error power detected by said first level detector is maintained at a minimum;wherein said main amplifier signal path further includes a third variable attenuator and a third variable phase shifter; andwherein said feedforward amplifier further comprises a third level detector for detecting, when an input signal to said feedforward amplifier includes a control channel signal and a main signal consisting of multiple carriers of different frequencies, the control channel signal from said distortion injection circuit; and a third controller for controlling said third variable attenuator and said third variable phase shifter in said main amplifier signal path such that the control signal detected by said third level detector is maintained at a minimum.