On the noise properties of injection-locked oscillators

This paper presents a detailed study of noise properties of injection-locked oscillators. We describe an elaborate numerical model, which offers the accuracy of the best known analytical models when analyzing a single oscillator. Those analytical models do not use perturbation theory since the Wiener nature of the noise renders small-signal analysis inadequate. Our model can be extended to any locked oscillators configuration while keeping the same accuracy. This was not done to date with any of the rigorous analytical models. We analyze unidirectionally and bidirectionally coupled oscillators operating in fundamental or harmonic-locking modes. Harmonic locking is analyzed in detail and the indirect locking process underlying it is identified while the noise of all harmonics is explored in detail. The results of the model are confirmed in a series of experiments employing electrooptic implementations with a photo-HBT-based oscillator. The various configurations we analyze and demonstrate experimentally represent important applications such as spectral purity enhancement, timing extraction, and low-jitter optical pulse generation.