| 摘要 |
PURPOSE:To reduce the time required for synchronism, by discriminating the simulated pull-in phenomena whether it is produced at the upper or not at the lower side of the reception carrier frequency and synchronizing the oscillation frequency of the voltage controlled oscillator. CONSTITUTION:The received input is given to a signal processing circuit 4 after the phase comparison of the output of a voltage controlled oscillator VCO6 and the output in phase shift of it by pi/2. On the other hand, the output of the VCO6 is compared with the output of a reference oscillator 8 at the frequency phase comparator FPC7, and different two outputs, when the frequency of VCO6 is lower or higher, are given to the 1st and 2nd voltage identifiers 9, 10. The devices 9 and 10 compare them with the set output at an output identifying point set circuit 11 to identify to what side of upper or lower side the virtual drawing is made, to drive a sweeper 13 and to output the synchronizing voltage of VCO6 from a voltage shift circuit 14. Thus, the time required for synchronism is reduced. |
