Phase Locked Loop (PLL)

A circuit that compares the output of a voltage controlled oscillator with a reference signal and uses the resulting difference signal to adjust the oscillator so that it will be locked to the reference in both phase and frequency. Phase-lock loops are used in frequency synthesizers.

This diagram shows how a phase locked loop circuit allows the precise creation of any frequency using a standard precision (crystal controlled) signal source. This example shows that a voltage-controlled oscillator (VCO) is used to provide a radio frequency (RF) signal based on an approximate DC voltage level. This RF signal is sampled and divided by a frequency divide. The frequency divider is programmed from the frequency control panel so it produces an output frequency that is the same as the crystal controlled (precision) frequency reference. This divided signal phase is compared against the reference frequency. As the phase begins to change, it produces a small DC voltage that is used to fine tune the VCO therefore phase locking it to the reference crystal frequency.

   Related WiMAX Definitions

Intra Frames - I-Frames
Predicted Frames - P-Frames
Bi-Directional Frames - B-Frames
DC Frames - D-Frames
Group of Pictures - GOP
Musicam
Elementary Stream - ES
Transport Stream - TS
MPEG Transmission

   WiMAX Books

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WiMax Explained This book explains the functional parts of a WiMAX system and its basic operation. You will learn how WiMAX systems can provide high speed data connections that can be used for voice, data and video services to distances of over 30 km.

CMOS PLL Synthesizers: Analysis and Design	Compression for Great Digital Video: Power Tips, Techniques, and Common Sense
CMOS PLL Synthesizers: Analysis and Design Keliu Shu, Edgar Sanchez-Sinencio,Hardcover,Series: The Kluwer International Series in Engineering and Computer Science, English-language edition,Pub by Springer-Verlag New York, LLC	Compression for Great Digital Video: Power Tips, Techniques, and Common Sense Ben Waggoner,Paperback,Series: DV Expert Series, English-language edition,Pub by Butterworth-Heinemann

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