| 摘要 |
PURPOSE:To expand a capture range without impairing the compression characteristic of AFC, by providing a holding type switcher which selects the output signals of first and second low-pass filters and outputs them to a voltage controlled oscillator. CONSTITUTION:A PLL(phase-locked loop) is constituted of a frequency converter 1, a band-pass filter 2, a phase comparator 8, a local oscillator 7, a second sample/hold circuit 9, the second low-pass filter 10, and the voltage controlled oscillator 6. By performing the initial pull-in operation of the voltage controlled oscillator 6 by the PLL and switching the AFC to a frequency discrimination type AFC, it is possible to realize to make the capture range into a broad area by the expansion of the pull-in characteristic of the PLL without deteriorating the frequency fluctuation supressing characteristic of the AFC. |
