| 摘要 |
PURPOSE:To ensure extremely certain discrimination, by applying the output of one phase comparator to a voltage controlled oscillator and an amplifier with amplitude limiter via a loop filter and adding the output of this oscillator to another phase comparator via a phase shifter. CONSTITUTION:An AM demodulator 1 outputs one input of two-frequency discriminating circuit. The output of a phase comparator 2 is fed as the control input to a voltage controlled oscillator 4 via a loop filter 3. The output of a loop filter 3 is fed as the input to an amplifier 8 with an amplitude limiter, on the one hand, the output can discriminate two frequencies. Further, another phase comparator is provided, and the output of the AM demodulation circuit 1 is fed to one input, and the output of the voltage controlled oscillator 4 is fed to another input via a 90 deg. phase circuit 5. Thus, the output of the AM demodulation circuit and the input signal to the phase comparator 6 are completely synchronized to enable the synchronizing detection. |
