Phase-Locked Loop

What Does Phase-Locked Loop Mean?

A phase-locked loop (PLL) is a type of electronic circuitry that consists of a voltage/current driven oscillator paired with a phase detector that constantly keeps its input and output in phase with each other. The function of a phase detector is to match the phase of the oscillator’s periodic signal with that of the input signal and correct the oscillator if it goes slightly out of phase. This is called a feedback loop, as output is fed back to the input.


Techopedia Explains Phase-Locked Loop

A phase-locked loop ensures a telecommunication signal in real time is locked at a certain frequency, if not, it tries to correct the frequency by constant comparing and feedback. PLLs are found in telecommunication channels as stabilizers, modulators, demodulators, noise removers and frequency dividers. They are used in wireless communication, especially in amplitude modulation (AM), frequency modulation (FM) as well as phase modulation (PM). Most commonly designed in the form of an integrated circuit (IC) that can handle digital communication, PLLs are one of the most important components for communication, both digital and analog. Wireless communication-aiding equipment utilizing phase-locked loop frequency control are also said to be frequency-synthesized.


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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.