| 摘要 |
<p>PURPOSE:To determine a correct ground speed removing effects of disturbance due to ruggedness or the like of ground surface, by having a Doppler signal passing through a band-pass filter which changes in the center frequency according to the speed to perform a speed display using a signal fetched. CONSTITUTION:The detection signal from a Doppler sensor 2 is fed to a low- pass filter 21 passing through an amplifier 20 and then, to band-pass filter 22 and a phase comparator 28 of a PLL circuit 27. The band-pass filter 22 employs a switched capacitor filter. The PLL circuit 27 is provided to make output frequency synchronize the frequency of an input signal and the center frequency of the band-pass filter 22 varies in the frequency of according to a reference signal (clock signal) corresponding to the vehicle speed. A signal with a fixed width fetched from the band-pass filter 22 is fed to speed display 26 passing through an F/V converter 24 and an A/D converter 25.</p> |
