A fast and accurate simulation method of impulse sensitivity function in oscillators

This paper presents a novel and simple simulation method to evaluate the impulse phase response of an oscillator. The technique, based on the linear-time variant (LTV) analysis of oscillators, computes the phase response in the frequency domain. It can be performed by means of periodic steady-state (PSS) and periodic transfer function (PXF) simulations available in commercial simulators (Spectre, Eldo, etc.). This method overwhelms the classical simulation method based on transient analysis and injection of charge pulses along the oscillator period in terms of both speed and precision. The good accuracy of the frequency domain method has been verified in two practical case studies, evaluating the 1/f3 phase noise in a classical Van der Pol oscillator and estimating the injection locking range in a ring oscillator-based frequency divider.