phase locked loop (PLL)
- Phase Locked Loop (PLL) is a phase synchronously controlled oscillator. In the PLL process, the phase position of a voltage-controlled oscillator( VCO) is compared in a comparator or phase discriminator with a reference phase position and a control voltage is obtained from the deviation, with which the oscillator is readjusted in its phase position several times a second.The control is phase- synchronous, so that one can speak of a phase-locked coupling between oscillator and reference phase position. The accuracy of PLLs is 0.001%, which is about 200 times better than that of a Variable Frequency Oscillator( VFO). Phase-locked oscillators are used in professional radio and television equipment. They are also used for synchronous clock regeneration and synchronous frequency multiplication.
- When data is transmitted using the phase-locked loop method, the timing information is transmitted with the data. The receiving device filters the timing information from the received signal and binds its internal clock to the timing signal.
_en.png)