Phase-locked Loops With Frequency Dividers
A phase-locked loop(PLL) uses a reference frequency to generate a multiple of that frequency. A voltage controlled oscillator (VCO) is initially tuned roughly to the range of the desired frequency multiple. The signal from the VCO is divided down using frequency dividers by the multiplication factor. The divided signal and the reference frequency are fed into a phase comparator. The output of the phase comparator is a voltage that is proportional to the phase difference. After passing through a low pass filter and converted to the proper voltage range, this voltage is fed to the VCO to adjust the frequency. This adjustment increases the frequency as the phase of the VCO's signal lags that of the reference signal and decreases the frequency as the lag decreases (or lead increases). The VCO will stabilize at the desired frequency multiple. This type of PLL is a type of frequency synthesizer.
Read more about this topic: Frequency Multiplier
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