Patent ID: 7248124

Claim:
A frequency calibration system, the system couplable to a reference oscillator to receive a reference signal having a reference frequency, the system comprising: an oscillator comprising a plurality of switchable reactance modules and a coefficient register, the plurality of switchable reactance modules having differentially weighted reactances, the oscillator adapted to provide an oscillation signal having an oscillation frequency; a frequency divider coupled to the oscillator, the frequency divider adapted to provide an output signal having an output frequency which is a rational fraction of the oscillation frequency; a comparator coupled to the frequency divider, the comparator adapted to compare the output frequency to the reference frequency and to provide a comparison signal when the output frequency is not substantially equal to the reference frequency; and a reactance modulator coupled to the comparator and to the oscillator, the reactance modulator adapted to determine and provide to the coefficient register a first plurality of coefficients to control switching of a first subset of the plurality of switchable reactance modules to increase the reactance of the oscillator when the comparison signal indicates the output frequency is greater than the reference frequency, and to determine and provide to the coefficient register a second plurality of coefficients to control switching of a second subset of the plurality of switchable reactance modules to decrease the reactance of the oscillator when the comparison signal indicates the output frequency is less than the reference frequency.