| 摘要 |
A phase shift center frequency control circuit of a quadrature frequency modulation mode detector includes a phase shifter for shifting the phase of an input voice frequency modulation signal corresponding to variation in the frequency for the phase shift frequency set in proportion to a predetermined control voltage, a phase detector for detecting the shifted phase of the voice frequency modulation signal by comparing it with the phase of the voice frequency modulation signal to demodulate the voice signal, a level detector for low-pass-filtering the voice signal to detect the DC voltage level, and a comparator for comparing the DC voltage level with a predetermined reference voltage level and applying the voltage corresponding the difference between them to the phase shifter as a control voltage.
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