PURPOSE: To attain large distortion compensation over a wide frequency band by using a 1st feedforward circuit to compensate a distortion component and using a 2nd feedforward circuit to compensate an output of the 1st feedforward circuit further.
CONSTITUTION: A distortion component generated in a main amplifier 19 is suppressed by a 1st feedforward circuit 38 and an output from a port (j) of a power coupler 15 is given to a port (n) of a power coupler 17. An input signal component and a distortion component from a port (p) of a 2nd feedforward circuit 39 are given a port (r) of a power coupler 18 via a delay line 33. The distortion component given to the port (r) and the distortion component given to a port (s) are added with equal amplitude and a phase difference of 180° by setting properly the coupling between the ports (r) and (t) and between the ports (s) and (t) and adjusting a variable attenuator 25 and a variable phase shifter 29. Thus, the signal whose distortion component is sufficiently suppressed is outputted from the port (t) through the cancellation of the distortion components.
KOSUGI HIROAKI
ADACHI HISASHI
NAGAO KAZUO
KUGO SHINICHI
