Feed-foward amplifier and controller of the same

摘要

A base pilot signal that is output from an oscillator (20) and a local oscillation signal that is output from an oscillator (21) are input to an injection-side mixer (22) so that two types of second pilot signals, sum frequency and difference frequency, are generated and injected into a distortion detection loop. Part of a signal appearing at an output terminal (2) is branched, converted in frequency by a detection-side mixer (23) using the local oscillation signal, filtered at a narrow-band filter (24), input to a synchronizing detector (25) with the filtered output as error signals (ErrI, ErrQ), and synchronizing detected with reference to the base pilot signal so as to generate control signals for a distortion rejection loop. The spectrums of the second pilot signals may be spread. A process to cancel the input signal component may be performed at the detection side. A simple circuit configuration enhances the distortion component rejection and suppression effect and shortens the time required until an optimum control state is established. <IMAGE>