phase-locked loop

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phase-locked loop

[′fāz ¦läkt ′lüp]
A circuit that consists essentially of a phase detector which compares the frequency of a voltage-controlled oscillator with that of an incoming carrier signal or reference-frequency generator; the output of the phase detector, after passing through a loop filter, is fed back to the voltage-controlled oscillator to keep it exactly in phase with the incoming or reference frequency. Abbreviated PLL.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


(Phase-Locked Loop) An electronic circuit that compares an input frequency and phase to a reference signal. It then generates a voltage proportional to the difference between the input and the reference. PLLs are used in myriad digital and mixed mode (analog and digital) applications as regulators, demodulators, synchronizers and frequency multipliers and dividers. For example, in a superheterodyne FM radio, a PLL is used to lock the local oscillator to an accurate frequency reference such as a crystal or ceramic resonator. It can also be used to demodulate the FM audio and stereo subcarrier signals from the intermediate frequency (IF) stage. See heterodyning.

PLLs in an FM Radio
This example shows how PLLs are used for regulation and demodulation in an FM radio tuned to 101.5 MHz. The FM frequency range is 88-108 MHz, and this example uses a 10.7 MHz intermediate frequency (IF) and a 1 MHz reference frequency.
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References in periodicals archive ?
Grimmett, "Frequency Modulation in a Phase-lock Loop by Control of the Phase Inside the Loop," RF Design, June 1991, pp.
This family of high-performance, low-skew, low-jitter phase-lock loop (PLL) clock drivers strengthens and extends IDT's already expansive product portfolio.
For greater flexibility and higher harmonic operation, the phase-lock loop (PLL) is generally employed.
Actually, this low phase noise is the YIG oscillator's free-running noise outside the phase-lock loop bandwidth, providing significant system design advantages.
Ramos, et al., "Fast Heterodyne Optical Phase-Lock Loop Using Double Quantum Well Laser Diodes," Electronics Letters, Volume 28, Number 1, 1992, pp.
The performance of the phase-lock loop is below this level.
The phase-lock loop is a second order loop and its parameters are determined by the VTDRO, phase detector and loop filter and amplifier, as shown in Figure 4, where
The three conventional techniques by which frequency synthesis can be accomplished are phase-lock loop (indirect), mix/filter/divide (direct/analog), and direct digital.
Low phase noise performance (see Table 1) was achieved by careful selection of internal VCO oscillator frequencies and tight control of logic, power and phase-lock loop signals.

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