| 摘要 |
A digital phase lock detector for determining the periods of an incoming signal for use in measuring rapidly and accurately the relative speed or velocity of vehicles according to the Doppler-radar principle includes a micro-controller based processor unit operated under a stored program to perform period determination. A bandpass filter is provided for generating a periodic signal which has a frequency which is varied in accordance with the velocity of the target vehicle in response to a difference Doppler signal. A comparator is responsive to the periodic signal for generating a rectangular pulse signal which is a digital representation of the periodic signal. The processor unit includes a microprocessor for determining the period of the pulse signal by integrating a number of consecutive cycles to produce a synthesized Doppler frequency signal having a frequency which is proportional to the velocity of the target vehicle. The bandpass filter is responsive to the synthesized Doppler frequency signal for varying the center frequency thereof to track the difference Doppler signal.
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