PROBLEM TO BE SOLVED: To estimate the characteristics of a propagation path by high time resolution without giving large non-linear distortion to a pilot signal in a power amplifier at radio communication.
SOLUTION: A pilot signal synchronizing circuit 15 synchronizes the pilot signals of all sub-carriers extracted by a pilot signal extraction circuit 14. A pilot signal resynthesizing circuit 16 sets up the phases of the sub-carriers of the synchronized pilot signals to the same phase on the center of a pilot signal section to synthesize the pilot signals. A peak amplitude detection circuit 17 detects a peak amplitude value from the synthesized pilot signal. A propagation path characteristic calculation circuit 18 calculates a parameter estimation value of the propagation path by using the detected peak amplitude value and estimates the characteristics of the propagation path by calculating a propagation path parameter minimizing a square error between a copy of a pilot signal prepared from the estimation value and the pilot signal.