| 摘要 |
PURPOSE:To enable to perform phase synchronization to the reception signal quickly, by reducing the effect due to the interference waves when the reception signal is weak, through disabling the phase synchronizing circuit for the synchronism if the reception signal is less than the predetermined level. CONSTITUTION:In the radio unit picking up the demodulation output from the reception signal by the phase synchronism circuit, the reception signal which is less than the predetermined level is detected for example, with the directional coupler SDC, filter NBP, rectifying circuit DD, and hysteresis circuit HYS. The output of the hysteresis circuit HYS closes the switch BSW, the voltage of the bias power supply BS is fed to the voltage controlled oscillator VCO of the phase locked loop PLL, disabling synchronism. Further, when the level of the reception signal is more than the given level, the switch BSW is opened and normal operation is again initiated in a very short time. Moreover, the switch SW is opened simultaneously with the switch BSW closed, it is recuired to stop transmission. |
