Fast and accurate behavioral simulation of fractional-N frequency synthesizers and other PLL/DLL circuits

Techniques for fast and accurate simulation of fractionally synthesizers at a detailed behavioral level are presented. The techniques allow a uniform time step to be used for the simulator, and can be applied to a variety of phase locked loop (PLL) and delay locked loop (DLL) circuits beyond fractional-N synthesizers, as well as to a variety of simulation frameworks such as Verilog and Matlab. Simulated results from a custom C++ simulator are shown to compare well to measured results from a prototype fractional-N synthesizer using a Sigma-Delta modulator to dither its divide value.