| 摘要 |
PURPOSE:To reduce the possibility of the step-out of a receiver even if a transmitted wave becomes out of synchronism by using a crystal oscillator as the transmitting local oscillator of a stand-by transmitter and a voltage-controlled oscillator which uses a crystal vibrator as the transmitting local oscillator of an in-use transmitter, and locking the phase of the output of the voltage- controlled oscillator to the output of the crystal oscillator and thus synchronizing the transmitted wave. CONSTITUTION:The stand-by transmitting local oscillator 13 consists of the crystal oscillator 13-1 and in-use transmitting local oscillators 11 and 12 consists of voltage-controlled oscillators (VCOXO) 11-1 and 12-1 formed connecting varactor diodes to crystal vibrators in series and phase detectors 11-2 and 12-2. The VCXOs 11-1 and 12-1 oscillate synchronously while supplied with part of the output of the crystal oscillator 13-1 and if the crystal oscillator 13-1 becomes faulty, the VCXOs 11-1 and 12-1 enters a free-run state, but the output frequencies have a little variation. Further, no switching to the stant-by transmitter is performed since the stand-by transmitting local oscillator is faulty, so the two in-use transmitters need not be synchronized.
|
