Analysis of a PLL Based Frequency Synthesis

A phase-locked loop (PLL) is a control system that tries to generate an output signal whose phase is related to the phase of the input “reference” signal. It is an electronic circuit consisting of a variable frequency oscillator and a phase detector that compares the phase of the signal derived from the oscillator to an input signal. The signal from the phase detector is used to control the oscillator in a feedback loop. The circuit compares the phase of the input signal with the phase of a signal derived from its output oscillator and adjusts the frequency of its oscillator to keep the phases matched.