| 摘要 |
PROBLEM TO BE SOLVED: To prevent the drop in loop gain and to improve signal purity by making an output of a voltage-controlled oscillator a local input, modulating it with a modulation signal that is synchronous with a reference frequency, dividing a frequency component signal that is shifted from a local input frequency with a prescribed frequency-dividing value and controlling the voltage- controlled oscillator with a reference frequency and a phase comparison result. SOLUTION: A modulator 3 makes an output signal 6 of a frequency f of a voltage-controlled oscillator 1 a local input, makes an IQ signal a modulation signal 8 and generates f to fm frequency spectrum. A phase comparator 5 compares (f-fm) /2 frequency that has undergone n frequency division of an output signal of the modulator 3 by a signal from a frequency-dividing table 9 by a variable frequency divider 4 with a reference frequency signal 2. The comparator 5 outputs a control signal 7 from the voltage-controlled oscillator which corresponds to phase difference to be outputted and controls an oscillation frequency of the oscillator 1. With this, loop gain is largely secured, and also signal purity is improved. |
