A study of the frequency stability limits of oscillators based on sapphire dielectric resonators

A novel approach to the design of ultra-stable microwave oscillators is presented. The method allows the short to medium term frequency stability to be accurately predicted a priori even before the beginning of the construction stage. This is achieved by characterising the fluctuations in various components and control systems of the oscillator in terms of their Allan variances. Stability limits are then determined by combining these results with the known Q-factors and frequency-temperature characteristics for both room temperature and cryogenic temperature compensated sapphire dielectric resonators.