Modulator evaluation method in /spl Delta/-/spl Sigma/ fractional-N frequency synthesis

The choice of a /spl Delta/-/spl Sigma/ modulator architecture has a significant impact on the performance of the /spl Delta/-/spl Sigma/ frequency synthesizer. The paper focuses on a modulator design method that allows full modulator and synthesizer characterization. It is shown that the MASH architecture can be designed to maintain a constant, arbitrarily long, output sequence for each input DC value. A modulator designed in such a way spreads the quantization noise over a known, arbitrarily large number of tones within the Nyquist bandwidth. Post modulator filtering is considered as a case study.