| 摘要 |
PURPOSE:To automatically regulate frequency characteristic of a voltage control filter by controlling the oscillation phase of a VCO by a control voltage of a phase synchronizing circuit. CONSTITUTION:In a PLL 28, a phase comparator 25 compares a data pulse from an AND gate 23 with the phase of a data transfer clock to be output from a VCO 27, and outputs a voltage responsive to a phase difference. The output of the comparator 25 is removed at its ripple and integrated by a loop filter 26, then supplied as a control voltage to a control input terminal of the VCO 27 to control the oscillation phase of the VCO 27. Accordingly, data transfer block of a frequency proportional to the data transfer speed from the VCO 27 is obtained. On the other hand, the output of the filter 26 is supplied as a control voltage to an LPF 14 and a BPF 15, and frequency characteristics of the filters 14, 15 are varied in proportion to the data transfer speed of a digital signal. Thus, frequency characteristics are automatically regulated. |
