| 摘要 |
PURPOSE:To stabilize the oscillation frequency and to improve responsiveness to a skew by switching the outputs of filters when video heads are switched, and supplying a voltage-controlled oscillator with the output of a 2nd filter which passes even a frequency component higher than a frequency component passed through a 1st normal filter. CONSTITUTION:When the scanning of the video heads is switched from a specific track to an adjacent track, a control circuit 5 generates a control signal for a specific time, and consequently a switching circuit 4 is put in switching operation tc supply the output signal 200 of the 2nd filter 3 to the voltage- controlled oscillator 6 through the switching circuit 4. The 2nd filter 3 passes the higher frequency component than the 1st filter 2, so when the output signal 200 of the 2nd filter 3 is supplied to the voltage-controlled oscillator 6, the response characteristics of a PLL system becomes faster than usual. Consequently' the frequency is stabilized with the simple circuit constitution and excellent response characteristics to variation of a synchronizing signal are obtained. |
