| 摘要 |
PURPOSE:To perform stable frequency detection even in the case of variation of received wave input level and to make low-noise detection possible without altering a circuit greatly by extracting a frequency detection output corresponding to a modulated wave input signal. CONSTITUTION:The received wave from a received wave input terminal 11 has its amplitude variation component removed by a limiter amplifier 1 and is inputted to a phase detecting circuit 2. The circuit 2 compares the phase or frequency of this input signal with that of the output of a voltage-controlled oscillator VOC3 which inputs the output of the circuit 2 and controls the oscillation frequency and outputs their difference signal. Then the phase or frequency locked signal of the circuit 2 is demodulated by a demodulating circuit 6 and outputted. Thus, the VCO3 performs control to be the same frequency as the inputted reception frequency and the output of the VCO3 is taken out through a buffer amplifier circuit 4A without exerting any influence on the operation of the whole device and then the reception frequency can be detected and outputted to a frequency detection terminal 13. |
