Analysis and Design of Direct Reference Feed-Forward Compensation for Fast-Settling All-Digital Phase-Locked Loop

A method for shortening of the settling time in all digital phase-locked loops is proposed. The method utilizes self monitoring to obtain the parameters necessary for feed-forward compensation. Analysis shows that by employing this technique both fast settling and good stability can be achieved simultaneously. Matlab and Verilog-AMS simulation shows that typical settling speed can be reduced to less than one tenth compared to a system without the feed-forward compensation, by merely employing the feed-forward compensation system. Further more a design example shows that this settling time can be decreased further to less than one fifteenth through design considerations when compared to a speed optimized phase-locked loop design system without direct reference feed-forward compensation. key words: all-digital phase locked loop, feed-forward, fast settling, frequency synthesizer