| 摘要 |
PURPOSE:To achieve excellent automatic tracking, by synchronizing the amplitude of a wobbling signal to a switching period of a magnetic head and increasing the amplitude near a switching point. CONSTITUTION:When a head switching signal in 30Hz is applied to a PLL10 and the like, a sinusoidal wave (f0) in 60Hz synchronized with a head switching timing is outputted from a PLL11. A signal in fundamental frequency (f) is amplitude-modulated with the sinusoidal wave (f0) at an amplitude modulator 12. Thus, the signal becomes a modulated wobbling signal modulaed in 60Hz to wobble a reproducing head. The amplitude of envelope change in the fundamental frequency (f) is maximum at a switching point (t) of a reproducing magnetic head 1, and a trcking error signal is obtained by passing through this change to a synchronizing detecting circuit 6 and the like. This signal is superimposed on a modulation wobbling signal at an adder 9 via a phase compensating circuit 8 to control the position of the head 1 so that it comes to the center of the recording track. Thus, excellent automatic tracking can be made. |
