| 摘要 |
PURPOSE:To obtain an FM frequency with broad band and simple and inexpensive circuit by providing a resistance split circuit, its driver, a shift register and a reference signal generator and employing a programmable frequency divider as the frequency divider. CONSTITUTION:With a modulation signal Sin fed to an adder 23, the adder 23 supplies a signal S23 being the addition of the signal Sin to an output signal S22 of a loop filter 22 to a VCO 24. Thus, similar out-band FM similar to a conventional circuit is attained. On the other hand, a signal S30 being the result of amplification of the signal Sin is adjusted to a level corresponding to a channel by a resistance split circuit 31 in which a prescribed resistance is set and the resulting signal S30 is given to a reference signal generator 32. The generator 32 outputs a reference signal Fa having a frequency corresponding to the signal S31 is outputted to a phase comparator 21. Thus, an output signal S24 of the VCO24 is frequency divided by the division frequency set by a frequency division data N at a programmable frequency divider 25 and a frequency division signal S25 is fed back to the comparator 21. The comparator 21 compares the phase of the signal Fa with the phase of the S25 and gives the signal S21 to the filter 22, then the in-band FM carrier is obtained. |
