Patent ID: 7336721
Filing Date: 2008-02-26
Classification: H03C

Abstract:
1. A digital frequency modulator comprising: a phase accumulator for accumulating an input digital signal and generating a phase accumulation according to a required phase resolution to output the phase accumulation within a predetermined output range, wherein the phase accumulator comprises an adder for adding the input digital signal to a previous input digital signal, an interpolator for interpolating the output of the adder at an interpolation rate determined according to the required phase resolution, a modulo operator for modulo-operating the output of the interpolator using a modulo index determined according to an output range of the phase accumulator and outputting a modulo-operated value as the phase accumulation, and a delay for delaying the output of the modulo operator by a product of a frequency of the input digital signal and the interpolation rate and outputting a delayed signal as the previous input digital signal to the adder; a phase modulator for outputting cosine and sine values corresponding to a gain multiplied phase accumulation; a first gain controller for multiplying a digital signal by a first gain determined according to a required modulation frequency to generate the input digital signal input to the phase accumulator; and a second gain controller for multiplying the phase accumulation by a second gain determined according to the required modulation frequency and the first gain to generate the gain multiplied phase accumulation input to the phase modulator.