Analysis and design of sub-harmonically injection locked oscillators

Sub-harmonic injection locking (SHIL) is an interesting phenomenon in nonlinear oscillators that is useful in RF applications, e.g., for frequency division. Existing techniques for analysis and design of SHIL are limited to a few specific circuit topologies. We present a general technique for analysing SHIL that applies uniformly to any kind of oscillator, is highly predictive, and offers novel insights into fundamental properties of SHIL that are useful for design. We demonstrate the power of the technique by applying it to ring and LC oscillators and predicting the presence or absence of SHIL, the number of distinct locks and their stability properties, lock range, etc.. We present comparisons with SPICE-level simulations to validate our method's predictions.