| 摘要 |
A Doppler velocimeter determines a state of noise generation in a detection signal including a Doppler signal component based on comparison by a preceding/succeeding-signal comparator for comparing the detection signals before and after passing through a band-pass filter for cutting noise adjusted to the frequency of the detection signal, and/or includes a filter circuit for determining passage/interruption of the detection signal after passing through the band-pass filter from a relationship between the count value of a first counter, in which the output of a first frequency multiplier for multiplying the frequency of the detection signal by N is made to be a clock signal and a leading edge in the detection signal is made to be a reset trigger, and a leading edge in the detection signal, and/or includes an error signal generator for generating an error detection signal by detecting a periodic error in the detection signal after passing through the band-pass filter from a relationship between the count value of a second counter, in which the output of a second frequency multiplier for multiplying the frequency of the detection signal by N and a leading edge in the detection signal is made to be a reset trigger, and a leading edge in the detection signal after passing through the band-pass filter, and/or includes a phase comparator for generating a control signal by comparing the phase of the detection signal with the phase of a comparison signal to be compared, an oscillator for controlling the frequency of its output signal in accordance with the control signal from the phase comparator, and a comparison-signal generation unit for generating a comparison signal based on the output of the oscillator. When an error has been detected, a switching unit interrupts the control signal and the phase comparator is reset and stops comparison, and when the error has ended, the switching unit communicates the control signal, the phase comparator starts comparison, and the comparison-signal generation unit generates a comparison signal whose phase coincides with the phase of the detection signal.
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