| 摘要 |
PROBLEM TO BE SOLVED: To provide an FM modulation circuit unnecessitating a doubler and a band pass filter with simple constitution. SOLUTION: In the range of prescribed carrier frequencies, the carrier frequency of a double step frequency interval is selectively oscillated, the carrier frequency is FM-modulated by a modulation signal to output from a voltage controlling oscillator 3 and the oscillation frequency of a reference frequency oscillator is frequency-divided into the frequency of (2×step frequency) by a frequency divider 2. In addition, an oscillation carrier frequency from the oscillator 3 is frequency-divided into the frequency of (2×step frequency) by a frequency divider 6, the output of the divider 2 and the output of the divider 6 are phase-compared by a phase comparator 7, the oscillation carrier frequency of the oscillator 3 is controlled by the output of a loop filter 9 inputting the output of the phase comparison and an oscillation output from the oscillator 3 is frequency-halved by a frequency divider 14 to make FM modulation output.
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