PURPOSE: To make it possible to rapidly decide the presence or absence of a burst signal by a minimum calculating overhead by relating an encoded input signal to the quantitative measuremenf of a plurality of known signals, and comparing it with the obtained threshold value of the measured value.

CONSTITUTION: An input signal is decoded to the sampling stream of a 1-bit decoder by a l-bit digitizer. The output at the time of a signal > 0, is a theoretical value '1', and at the time of the signal < 0, is '0'. The whole pattern capable of generating from the 1-bit decoder is related to the quantitative measurement. That is, the quantitatively measured value calculated previously for all the binary pattern is loaded to a memory, correlated to the possible patterns, and the quantitatively measured values of the respective patterns are obtained. In this case, for example, Fourier analysis is used, the optimum reference for detecting a sine waveform at the time of existing noise is obtained, and the coincidence of the input signal with the sine waveform to be detected is established based on it. The established measured value is compared with a predetermined threshold value, and the presence or absence of a burst signal is decided.