Behavioral simulation of fractional-N PLL frequency synthesizers: Phase approach

Simulation results of a behavioral model of fractional-N PLL synthesizer are shown in this paper. It has the potential of reliable and fast evaluation of phase noise performance of a fractional-N charge-pump PLL. A method of overcoming the numerical inaccuracy due to finite sampling frequency has been applied and is briefly described. The technique allows setting the sampling period according to the lower, reference frequency, instead of high-frequency VCO output thus substantially saving both simulation time and memory for data storage.