PURPOSE: To enhance receiving accuracy by dividing a wide-band signal into narrow-band components and detecting a pulse like signal at every frequency using the time series data of instantaneous power densities at every divided frequencies to control the integration constant of long-time integrated power calculating function.

CONSTITUTION: The wide-band signal of the output of a sensor 1 is divided into narrow-band components by a frequency analyzer 11 to perform the analysis of frequency and instantaneous power densities are calculated at every divided frequencies using the frequency analysis result by an instantaneous power density calculator 12 and a pulse detector 13 detects the pulses of pulse-like signal components at every divided frequencies using the time series data of instantaneous power densities. An integration constant is set with respect to pulse detected frequencies by an integration constant setting device 14 and the instantaneous power densities are integrated within a time region using this integration constant by an integrator 15 to calculate long-time integrated powers at every frequencies and the long-time integrated powers are added within a frequency region by a power calculator 16 to calculate the power of the wide-band signal.