| 摘要 |
PURPOSE:To facilitate manufacture and maintenance by setting a transmission output frequency to an optional channel by using a reference oscillator having the same frequency. CONSTITUTION:The circuit consists of the reference oscillator, VCO5, PLLs 24 and 25, and VCO10 for an offset. The reference frequency signal 13 from the oscillator 1 is frequency-divided by a frequency divider 2 to obtain a signal 14. The output signal 17 of the VCO5 is frequency-divided by a frequency divider 4 at the frequency division ratio determined by a channel setting signal 11 to obtain a signal 15. Then, a phase comparator 3 applies a frequency control signal 16 to the VCO5 so that the outputs 14 and 15 of the frequency dividers 4 and 5 are in phase with each other. The output 17 of the VCO5 is therefore set to the frequency determined by the signal 11. The system consisting of VCO10 and PLL25 operates similarly only except difference in frequency. Consequently, the transmission output frequency is set to an optional channel and a transmitter which functions to offset from a circuit frequency at extremely small frequency intervals is constituted by using the reference oscillator having the same frequency. |
