| 摘要 |
PURPOSE:To realize a device for demodulating circuit in a small size with a low cost, by providing the low pass filters that secure a synchronization between the oscillation frequency of the voltage controller of a demodulator and the carrier frequency to be demodulated and then eliminate the carrier which is unnecessary for the output circuit of a phase detector. CONSTITUTION:The received signal is amplified by the amplifier 7 and then branched off to the demodulators 23 and 24 with low pass filters via the signal branching hybrid 8. At the demodulators 23 and 24, the output of the orthogonal branching hybrid 15 is led to the phase detectors 16 and 17 along with the output of the voltage control oscillator 19 plus the output that passed through the 90 deg.-phase shifter 18; and the outputs of detectors 16 and 17 are led to the base band amplifiers 20 and 21 via the low pass filters 25 and 26 respectively. The outputs of the amplifiers 20 and 21 turn into the circuit outputs of the demodulators 23 and 24 and at the same time receive a feedback connection to the control terminal of the oscillator 19 after a branching and via the carrier reproducing part 22. In such a way, a branching filter is eliminated for each carrier frequency to realize a device in a small size with a low cost. |
