Stability analysis of self-injection-locked oscillators

This paper addresses the stability analysis of the self-injection-locked oscillators. The analysis is developed for arbitrary self-injection feedback loops and illustrated with the specific case of a simple time-delay cable. It is shown that the output phase stability in self-injection-locked oscillators depends on the feedback loop delay and the types of oscillator circuits, which are represented by equivalent parallel- or series-resonant oscillator models. The self-injection-locked technique can also be used to test the oscillator circuit model when the self-coupling phase is known. The theory is verified by using a self-injection-locked GaAs MESFET oscillator operating at X-band with delay loops.