Low Phase Noise Signal Generation

At the present state of the art it is not feasible to generate a signal directly at the microwave operating frequency having the required short-term or long-term stability The best is a high-performance crystal oscillator, usually realized as an ovenized crystal oscillator (OCXO). The OCXO forms the master oscillator for the system; from it, all required system frequencies are derived coherently by a combination of frequency multipliers, phase-locked oscillators, mixers, filters, and frequency synthesizers. If these components and subsystems are properly designed, both the short-term and long-term stability limitation is due to the master crystal oscillator. This proposal deals with methods for improving the master crystal oscillator. Two types of phase noise must be distinguished from one another: quiescent phase noise, arising from the various components of the system when stationary, and vibration-induced phase noise In a well-designed oscillator, the acceleration sensitivity is almost entirely due to the resonator(s). This proposal deals with improvements to the master crystal oscillator. Crystal oscillator phase noise can be improved by 1) resonator improvements, 2) use of multiple resonators, 3) use of multiple oscillators, or 4) Vibration filtering or cancelleation.