System and method for calibrating output frequency in phase locked loop

A Digital Calibration System (DCS) for a Phase Locked Loop (PLL), wherein the PLL comprises a PLL controller for outputting a tuning voltage in response to a reference signal and a feedback signal, and a voltage controlled oscillator (VCO) outputting the feedback signal as an output signal in response to the tuning voltage, the tuning voltage is used to determine whether the frequency of the output signal needs to be increased or decreased,

• the DCS comprising:
• a Tuning Voltage Controller (TVC) configured to set the tuning voltage to a value;
• a Phase Difference Quantizer (PDQ) configured to output a phase difference after comparing a phase of the reference signal with a phase of the feedback signal;
• and
• a Digital Controller (DC) configured to receive the phase difference of the PDQ and output a coarse tuning signal to adjust the feedback signal such that an average phase difference of the PDQ is 0.