Patent ID: 8346188

Claim:
A frequency modulation transmitter comprising: a frequency synthesizer for generating a frequency modulated signal of a digitally encoded audio signal, wherein the frequency synthesizer further comprises a digitally controlled oscillator having a variable capacitor array that receives a calibrated fine code for tuning the variable capacitor array to generate the frequency modulated signal with a modulation frequency; a nonlinearity estimator for generating an approximation of an integral nonlinearity associated with processing of a fine code for tuning the variable capacitor array to the modulation frequency; and a subtractor for subtracting the fine code with the approximation of the integral nonlinearity to generate the calibrated fine code, wherein the nonlinearity estimator calculates nonlinearity associated with the calibrated fine code and subtracts the nonlinearity associated with the calibrated fine code from the fine code to refine the calibrated fine code that is provided to the digitally controlled oscillator, wherein the frequency synthesizer further comprises: a first frequency divider for generating a reference interval by dividing a frequency of an input clock; a frequency comparator for generating a frequency error by comparing an output frequency of the frequency synthesizer with a tuning frequency; an amplifier for amplifying the frequency error; an integrator for accumulating the frequency error, wherein the frequency error is processed by the digitally controlled oscillator to correct the frequency error; and a second frequency divider for dividing the modulation frequency of the frequency modulated signal.