Comparisons of phase noise models of CMOS ring oscillators

Comparisons of phase noise models based on time domain models and frequency domain models are presented. It is shown that time domain approach by this author, based on conventional time scaling and that incorporates multiple threshold crossing phenomenon, reflects the physical mechanism better. Moreover its phase noise expression does not blow up as offset frequency goes to zero. Finally compared to frequency domain methods the transient simulations needed to obtain the necessary parameters are simpler.