| 摘要 |
PURPOSE:To simplify a synchronous detection circuit, to reduce energy consumption and to eliminate the necessity of adjustment by selecting either the stable reference carrier signal of a frequency almost equal with the carrier of a modulation wave or the modulation wave responding with a synchronization control signal and inputting the selected signal to the frequency detection circuit. CONSTITUTION:In a state that a signal is received, an angle modulation wave to arrive at a terminal 1 is inputted to a frequency detection circuit 5 and in a carrier reproducing circuit 6, the angle modulation wave is detected with the carrier reproduced from this received signal, in a cosine phase comparing frequency detector 7. When the received signal is interrupted, the control signal is applied to a terminal 3 and the reference carrier signal applied to a terminal 2 is selected as the input of the detection circuit 5. In such a case, the signal of the frequency equal to the reference carrier signal is regenerated in a carrier reproducing circuit 6 of the frequency detection circuit 5 and the oscillation frequency of a voltage control oscillator 11 is set to the frequency equal with the reference carrier signal. Thus, since the detection circuit can be composed of a reference oscillator and selection switch, the effects to simplify the circuit and to reduce the energy consumption are exhibited. |
