Phase Lock Loop (PLL)

IntroductionGenerate accurate and variable frequencies for : Local oscillator super heterodyne receiver Signal generator

Crystal Oscillator – Provide reference frequency Voltage control oscillator (VCO) – Generate

frequency Divider – Control multiplication of generated

frequency from reference frequency Loop filter/LP filter – Integrate/Averageing voltage

from phase detector Phase Detector (PD)– Compare feedback

frequency and frequency generated by VCO. Produce voltage if the these frequency differ.

Phase lock loop Elements

*Most charge pump component build together with Phase detector in single package* P Counter = N Divider

Fvco= N Divider x Fref

Phase Lock Loop with mixer feedback