| 摘要 |
PURPOSE:To reduce a cost by simplifying constitution by controlling a frequency signal generating means so as to obtain phase-locking with the first period of a modulation information signal, performing phase comparison with the modulation information signal in a second period, and forming an information signal corresponding to the above comparison result. CONSTITUTION:A phase-locking control circuit 19 generates a gate pulse A inverting at every 4H or 2H and a gate pulse B with a phase opposite to that of the gate pulse A synchronizing with a horizontal synchronizing signal, and supplies the gate pulse A to an oscillator 17a and the gate pulse B to an oscillator 17b. The oscillators 17a and 17b fetch an ID signal during the period of low level of the gate pulses A and B supplied from the phase-locking control circuit 19, and the oscillators 17a and 17b oscillate so as to be synchronized with a fetched ID signal. Signals outputted from the oscillators 17a and 17b are outputted alternately synchronizing with an output switching pulse outputted from the phase-locking control circuit 19 at an output switching circuit 20. The modulation information signal can be demodulated to an original information signal with such simple circuit constitution. |
