| 摘要 |
<p>A phase-locked loop comprises a signal path including a phase comparator, a loop filter and a voltage-controlled oscillator that are cascaded. The phase comparator compares the phases of an input signal with the phase of the output signal from the voltage-controlled oscillator and produces the result of comparison. The loop filter produces DC voltage in response to the output signal from the phase comparator. The voltage-controlled oscillator controls output oscillation frequency according to the DC output voltage from the loop filter. Voltage tracking means combines the voltage of the signal path with a signal for making the average voltage output from the phase comparator equal to a predetermined reference voltage. The voltage tracking means serves to expand the lock range of the phase-locked loop.</p> |
