Phase-Stable Oscillators for Space Communications, including the Relationship between the Phase Noise, the Spectrum, the Short-Term Stability, and the Q of the Oscillator

Highly phase-stable, crystal-controlled oscillators are playing an increasingly important role in extending the range of deep-space communications. For example, during a recent radar experiment with the planet Venus, then at a range of 35-million miles, real-time detection was accomplished with a receiver bandwidth of 5 cps and a search frequency of 2388 Mc. Spectral measurements of the Venus-reflected signal indicated at times a spectrum of only a few cycles in width. The ability to resolve such narrow phenomena was gained through the use of extremely phase-stable oscillators combined with extremely precise predicted control of the frequency of the receiver local oscillator. The purpose here is to discuss oscillator phase noise, its origin, and techniques for its observation and measurement. Relationship between the phase noise, the spectrum, the short-term stability, and the Q of the oscillator is established.