| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency modulation circuit in which no inverse modulation occurs in frequency modulation at low frequency with multi-channel PLL synthesizer, and a specified frequency is held even in a continuous slot. <P>SOLUTION: The frequency modulation circuit comprises a reference oscillator 3 which generates the signal of specified reference frequency, a voltage control type oscillator 1 which outputs a control voltage frequency that is the frequency based on a control voltage, a phase comparison circuit 5 which outputs control voltages (a) and (b) as a phase comparison voltage representing phase difference between the signal of reference frequency and the signal of a frequency acquired by dividing the control voltage frequency, and holding circuits (9, 10, and 11) for holding the control voltage. Thus, inverse modulation is prevented in modulation at low frequency with a multi-channel PLL synthesizer. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
