| 摘要 |
PURPOSE:To make the free-run frequencies of a VCO unadjusted by applying a voltage corresponding to the dislocated portion of the VCO oscillating frequencies with respect to a disk rotation control reference clock in order to fetch a signal at a constant transmission rate from a recording media to a VCO controlled voltage. CONSTITUTION:For the clock frequencies of a reference oscillator 12 to have the clock frequencies corresponding to the transmission bit rate of the signal applied to an input terminal 1 and to be also the reference frequencies of the servo circuit of the recording media, which determines the transmission rate of the input signal, and for the clock frequencies of a voltage controlled oscillator (VCO) 6, the voltage corresponding to their difference is outputted by a frequency comparator 9, and it is added through a loop filter 10 and an adder 5 to the voltage to control the oscillating frequencies of the VCO 6. Thus, the oscillating frequencies of the VCO 6 is always set near the transmission rate, and the free-run frequencies can be made unadjusted. |
