Patent ID: 8618878

Claim:
A multiport amplifier comprising: an input hybrid to which a plurality of input signals corresponding to a plurality of channels are inputted, said input signals each having a necessary component at a desired frequency of a respective channel; an output hybrid which outputs a plurality of output signals corresponding to said plurality of input signals from a plurality of output terminals; a plurality of amplifiers and a plurality of gain and phase control circuits which are inserted between said input hybrid and said output hybrid, wherein said plurality of amplifiers are combined in parallel with one another; a plurality of output coupling circuits that are inserted between said output hybrid and said plurality of output terminals so that they receive output extraction signals corresponding to said plurality of output signals; and a feedback circuit that is inserted between said plurality of output coupling circuits and said plurality of gain and phase control circuits; wherein said feedback circuit includes, at least one frequency selection circuit configured to pass only unnecessary frequency components other than each necessary component at said desired frequency, a control signal generation circuit configured to generate a control signal for controlling a gain and a phase in at least one of said plurality of gain and phase control circuits, and said control signal generation circuit generates control signals for said plurality of gain and phase control circuits based on presence of unnecessary frequency components included in said plurality of output signals so as to attenuate said unnecessary frequency components.