Studying Digitally Controlled Oscillator Circuits for Digital Phase Synchronizers

The Voltage Controlled Oscillator is replaced by Digitally Controlled Oscillator in the digital Phase Locked Loop systems. The Digitally Controlled Oscillator has several differences and limitations which require further study in order to compare the different circuit variations and to choose the most appropriate circuit for the application. The frequency range, frequency step and the frequency change delay are examined in this paper. The results from the testing of the different circuit variations are compared and represented in graphical form. The useful range of working frequencies is discussed.