using voltage controlled oscillator

A voltage controlled oscillator (VCO) is used in an application where we need an oscillator to provide a signal, but we require that oscillator to be able to shift frequency very rapidly. We can build circuits that change voltage very rapidly, and these can be use to shift the frequency of the VCO just a quickly. One application of the VCO is in devices to which we wish to apply automatic fine tuning (AFT). We often see receivers that have AFT circuits to optimize reception.

difference between local oscillator and controlled oscillator

Hadi Mojaradi has written:

'Wideband gallium arsenide MESFET voltage controlled oscillator for upper Ka band'

PLL stands Phase Locked Loop . It consists of phase detector,low pass filter,voltage controlled oscillator,error amplifier