| 摘要 |
PURPOSE:To secure the stabilized function for synchronizing IF frequency by controlling local frequency by means of three BPFs so that the IF frequency is always kept at a fixed value. CONSTITUTION:A signal received by an antenna 1 is multiplied by a multiplier by the same pseudo noise 5 as that for a transmitter, and, only when synchronized, becoms a narrow-band signal. If the output, which become the narrow- band signal, of a multiplier 4 passes any one of three BPFs 6-1-6-3, the energy in each filter band loses its balance. The difference is detected by diffeential amplifiers 13-1-13-3 and outputted from a terminal 11 as a synchronization discriminating signal. If the spectrum of an IF signal moves due to the instability of a transmission carrier or receiving oscillator at this moment, the frequency of an oscillator 15 for voltage control is lowered or increased by the output of amplifiers 13-1-13-3 to lock at optimum conditions. As a result, a stabilized IF signal can be extracted, even if the frequency variation of the transmission carrier or receiving oscillator is large. |
