VARIABLE MODULUS MODULATOR FOR FRACTIONAL-N FREQUENCY SYNTHESIZERS

摘要

A variable modulus sigma-delta modulator for a fractional-N frequency synthesizer in accordance with the present invention may include an integer division unit; a pulse-width modulation (PWM) generator, a sigma-delta noise-shaping unit, a first input FRAC for receiving a first programmable integer, and a second input MOD for receiving a second input, wherein the integer division unit is configured to perform a translation from the first input and the second input into a first output FRAC' and a second output R, the PWM generator is configured to receive the second input MOD and the second output R, and generate a modulated pulse signal, and the sigma-delta noise-shaping unit is configured to receive the first output and the modulated pulse signal, and generate a sequence whose average equals approximately the first input over the second input.