| 摘要 |
PURPOSE:To improve a signal-to-noise ratio in signal detection by dividing each of signal detecting frequency bands into plural sub-frequency bands. CONSTITUTION:Signals coming into an input terminal 1 are converted into signals suitable for calculation at an extending circuit 10 and only components of each sub-frequency band are filtrated by means of a digital filter 12, and then, signals corresponding to the level of components contained in each sub-frequency band of input signals are obtained by a squaring circuit 13 and digital integration circuit 14. Then the signals obtained by the circuits 13 and 14 are compared with the input of a threshold level input terminal 4 and the compared results are outputted from a level judging circuit 15. Existence of the signals is discriminated through the OR16 of the output of the level judging circuit 15. |
