PHASE LOCKED LOOP

Presented BY:

Nasir Ihsan

Presented To.

Engr. Armaghan Zafar

Communication System

IET DEPT.

GOMAL UNI PAKISTAN

OUTLINES

History of PLL

Definition of PLL

Parts of PLL

Applications

Conclusion

DEFINITION OF PLL

PLL is an Electronic Module (Circuit)

A PLL is a negative feedback system

CONTROL SYSTEM REPRESENTATION

PARTS OF A PLL

Phase Detector

Filter

Voltage Controlled Oscillator (VCO)

Programmable Counter/Divider (OPTIONAL)

PARTS OF A PLL

Phase Detector

Produces a voltage

Voltage becomes a control signal

PARTS OF A PLL

Filter Determines dynamic characteristics of PLL

Specify Capture Range (bandwidth)

Specify Tracking Range

Receives signal from Phase Detector and filters accordingly

PARTS OF A PLL

Voltage Controlled Oscillator Changes a DC input voltage into a pulsed waveform.

The output frequency is proportional to the magnitude of

input control voltage.

PARTS OF A PLL

Voltage Controlled Oscillator (Cont.) The output frequency of a VCO is given by:

fout = fmin + KVCOVin

where fmin = output frequency when Vin=0

KVCO = VCO conversion gain, Hz/V

PARTS OF A PLL

Programmable Counter (Divider) It is an optional part of PLL.

PRACTICAL APPLICATION:

Digital wireless communication system

like GSM

Cellular Handsets

OTHER APPLICATIONS OF PLLS:

Control Systems

Frequency Synthesizers

Jitter reducers

Zero Delay Buffers

Demodulators (QPSK, QAM, FM, FSK, SSB)

Finally: If you would like to further enhance your

understanding of phase-locked loops, there is an excellent

YouTube video by different Professors. You can find it at:

http://www.youtube.com/watch?v=NeRdsWYqWFU