A space-qualified frequency synthesizer

The author describes the performance and some of the design features of a dual-frequency synthesizer developed and built for the topography experiment (TOPEX) program. The space-qualified synthesizer generates high-quality 4.096-MHz and 19.056391-MHz radio-frequency signals from a 5-MHz reference source for use by Global Positioning Satellite and TDRSS transponder equipment aboard the TOPEX-Poseidon satellite. Two high-quality voltage-controlled crystal oscillators (VCXOs) phase locked to the reference oscillator are employed to ensure excellent long-term stability. The VCXOs provide a low spurious amplitude spectrum and low phase noise performance with high short-term stability outside the bandwidth of the phase-locked loops. The measured performance of the flight synthesizer approaches that of a good reference oscillator. The spurious amplitude spectrum (excluding harmonics) is less than -80 dBc from 1 Hz to 1.5 GHz offset from the carrier of each output frequency