Analysis and Modeling of Super-Regenerative Oscillators with FMCW Signals

Active transponders based on super-regenerative oscillators (SRO) have the advantages of high gain, low power consumption, and a compact implementation. They are based on a switched oscillator excited by a low amplitude FMCW signal, which provides an approximately phase-coherent response. Due to the system complexity, involving the start-up transient and a time varying phase shift, any realistic modeling is demanding. Here an accurate formulation is presented, which makes use of an instantaneous phase function, extracted through a circuit-level envelope-transient simulation of the standalone SRO in a single quench period. The formulation based on this phase function avoids all the simplifications considered in previous works. It provides the relationship between the baseband frequency and the distance to the target with no need for long time simulations of the transponder system. For illustration, the method will be applied to an SRO at 2.7 GHz, which has been manufactured and measured.