| 摘要 |
PURPOSE:To distinguish clearly between band noise and signal data, by receiving an external noise after discontinuing the transmission signal, comparing the noise with the signal to search the degree of noise mixture, and discriminating a correct signal. CONSTITUTION:The transmission ultrasonic wave of the reference frequency radiated from a wave transmitter 1 is reflected by a car and received by a wave receiver 2 to be converted into an electric signal. This electric signal receives a product modulation with the transmission signal by a mixer 7. The analog Doppler signal extracted out of a BPF8 is digitized by a waveform shaping circuit 9 and at the same time fed to a rectifying circuit 10 to receive a level detection to be turned into a sense input signal. The outputs of the circuits 9 and 10 are fed to a signal processing part 18. For a process of the Doppler signal, a doppler wave detecting circuit 14 performs a Doppler wave detection, and then the ON/OFF of a counter 4 is controlled to discontinue the transmission wave. Then only the external noise is received at a receiving part. A noise measuring circuit 13 inspects a single-shot noise, and the output of the circuit 13 is fed to the circuit 14 to receive a Doppler wave detection. Then the noise measured by the circuit 13 is compared with the signal by the output of the circuit 14. Thus the degree of noise mixture is searched to discriminate a correct signal. |
