| 摘要 |
PURPOSE:To reduce the undesired radiation level of a video disk player, by coupling variable capacity which shows the variation of capacity on the disk to an oscillator which generates the reference oscillating frequency and applying the frequency modulation to the oscillator. CONSTITUTION:A variable capaicty 1 showing the variation of capacity on a disk is coupled to an oscillator 4'. The modulation of frequency is applied to the oscillator 4' in response to the capacity 1 and with use of the reference oscillating frequency as a carrier wave. Then the frequency modulated wave is applied to a parallel resonance circuit 3 via a coupling coil 5. The circuit 3 consists of a fixed capacity 10 and a coil 2, and each value is set so that the FM modulated wave frequency obtained from the oscillator 4' corresponds to the slant part of the resonance characteristics of the circuit 3. Thus the amplitude modulated signal picked up from a pickup coil 6 is demodulated by an AM demodulation circuit consisting of a diode 7, etc. Then the FM signal recorded on the disk is obtained. |
