| 摘要 |
A composite signal consisting of a plurality of signals of different frequencies is applied via a cancelling circuit to a phase-locked loop circuit which is adapted to be locked with a certain signal contained in the composite signal to generate a signal synchronous with this certain signal. A cancelling signal generated from a cancelling signal generating circuit is applied, in addition to the composite signal, to the cancelling circuit when the phase-locked loop circuit is in the locked state, thereby cancelling, by this cancelling signal, those signals contained in the composite signal other than the certain signal. Thus, only the certain signal is inputted from the cancelling circuit to the phase-locked loop circuit when the latter is in the locked state.
|
