VCO jitter simulation and its comparison with measurement

Abstract

We have simulated the phase noise of a voltage controlled oscillator (VCO) using an RF circuit simulator, SpectreRF/sup TM/. This simulator uses a variation of the periodic noise analysis first proposed by Okumura, et al (1993). It computes the power spectral density of the noise as a function of frequency. By assuming that only white noise sources are present in the oscillator, it is possible to derive a simple relationship between the level of the phase noise and the jitter. This excludes flicker noise from consideration, however, since flicker noise is a low-frequency phenomenon, excluding it only affects the accuracy of the long-term jitter. We compared the jitter with measurement and found the error to be less than 2 dB. An AHDL model for the VCO that efficiently exhibits jitter in the time domain is included. The model was written in Verilog-A. This model can be used to determine the affect of VCO jitter on a larger system, such as a phase-locked loop (PLL).