Patent ID: 7719335

Claim:
A self-biased Phase Locked Loop, PLL, comprising: a Phase Frequency Detector, PFD, adapted to detect a frequency difference and a phase difference between an input signal and a feedback signal and to generate a pulse control signal; a Charge Pump, CP, adapted to generate a charging or discharging current which equals to a first control current input to the CP according to the pulse control signal output from the PFD; a Loop Filter, LF, comprising a filter unit and adapted to output a first control voltage, to boost the first control voltage at two terminals of the filter unit when the CP outputs the charging current, and to lower the first control voltage at the two terminals of the filter unit when the CP outputs the discharging current, wherein the filter unit comprises a resistor controlled by the first control voltage and a second control voltage, and the second control voltage is adjusted by the first control voltage and a second control current which is input to the LF; a Voltage Control Oscillator, VCO, comprising an oscillation unit with symmetric loads which are controlled by the first control voltage, and adapted to increase an oscillation frequency of an output signal when the first control voltage is boosted, to decrease the oscillation frequency of the output signal when the first control voltage is lowered, and to generate a bias current and a bias voltage which is provided to the oscillation unit by the first control voltage output from the LF; a divider adapted to divide frequency for the output signal of the VCO and to generate the feedback signal input to the PFD; and a bias current converter adapted to convert the bias current generated by the VCO into the first control current input to the CP and the second control current input to the LF, wherein the first control current equals to a ratio of the bias current to a constant, and the second control current equals to a ratio of the bias current to a frequency division factor of the divider wherein the LF further comprises a filter bias unit adapted to adjust the second control voltage by the first control voltage and the second control current which is input to the LF.