Transition from locking to pulling in injection-locked dividers

A comprehensive methodology of analysis of Injection-Locked Frequency Dividers (ILFDs) allows us not only to estimate the locking range, the amplitude and the phase of the locked oscillations and their stability, but also to investigate the transition from the locking mode to the pulling mode, that happens in proximity of the boundaries of the locking region. We highlight that there exists a border region where the two modes of operation can coexist and the occurrence of one mode, or the other, depends only on the initial conditions. Numerical simulations confirm analytical predictions.