Cavity control of active integrated antenna oscillators

The use of a cavity coupled to an active integrated antenna oscillator is described. The cavity increases the loaded Q factor of the oscillator, thus improving stability and reducing the phase noise. Cavity stabilisation of a microstrip patch and slot ring oscillators is described. In both cases, phase noise at a frequency offset of 10 kHz is reduced by the order of 20 dB. A first-order analysis based on measured and simulated cavity Q factors is shown to give similar results. A Van der Pol analysis of a two-element array of patch oscillators, with a single extended coupled cavity, indicates that the likelihood of mutual locking in an array which has oscillators with slightly different free running frequencies is enhanced albeit at the expense of increased start-up time.