Patent ID: 8762094

Claim:
A method of calibrating a frequency of a g m -C filter, the method comprising: generating, by a frequency calibration circuit, a calibration code for tuning a cut-off frequency of the g m -C filter according to a received reference code and a frequency of an oscillation signal that is output from a g m -C oscillator; determining, by the frequency calibration circuit, whether the calibration code exists within a range of the received reference code; and outputting, by the frequency calibration circuit, the calibration code to the g m -C filter when the calibration code is within the range of the reference code, and outputting a current control code when the calibration code is outside the range of the reference code to generate a variable current to tune a transconductance of the g m -C oscillator and a transconductance of the g m -C filter, wherein tuning the transconductance of the g m -C oscillator changes the frequency of the oscillation signal and tuning the transconductance of the g m -C filter adjusts a cut-off frequency of the g m -C filter.