| 摘要 |
PURPOSE:To avoid mis-discrimination of synchronization due to too increased gain of an intermediate frequency amplifier at asynchronizing state by selecting a reference voltage applied to a 2nd input terminal of an AGC amplifier depending on the asynchronizing state and the synchronizing state. CONSTITUTION:When no synchronization is taken, a high detection voltage V1 is not kept for a long time and a voltage V3 outputted from an integration device 20 is low as shown in a plot (b) in figure (a) and lower than a preset reference voltage, then no signal SL2 is outputted from a comparator 21. After lapse of a prescribed time, a control circuit 22 stops the output of control signals ST1, ST3. Then a switch 23 is closed and an output signal of the AGC amplifier 10 is inputted to a low pass filter(LPF) 11, a voltage controlled oscillator in a code generator 3 is oscillated at a self-running frequency to restart synchronization acquisition. Thus, misdiscrimination of asynchronizing state as synchronization is prevented. |
