Pll circuit and method for generating a modulated carrier signal

Abstract

A PLL circuit for generating a modulated carrier signal includes a digitally controlled oscillator (DCO) to generate the modulated signal. The PLL circuit receives a desired phase change as a modulation signal at each cycle of a non-uniform clock, derived from the a DCO output and a uniform reference clock. This phase change adjusts the DCO's frequency. The circuit also receives a frequency control word, representing the ratio of the desired carrier frequency to the reference clock frequency. The phase change and frequency control word are accumulated to predict the DCO's output phase. A non-uniform clock compensation circuit calculates a compensation value for the phase change. A phase detector estimates the error between the predicted phase and the time offset between the reference clock and DCO output, generating a control signal for the DCO based on this error.