1995 IEEE INTERNATIONAL FREQUENCY CONTROL SYMPOSIUM

Quartz oscillators which serve as the time and frequency references on satellite missions are called upon to meet stringent performance requirements. Recent applications call for the best possible stabilities and low noise performance while at the same time demanding features such as high resolution remote digital tuning, which can potentially compromise ultimate stability. In this paper, we present test results and a discussion of some design criteria and strategies for meeting requirements of high precision, survivability and reliability. The error budget for critical performance factors is examined within the context of a worst case analysis. This includes resonator aging vs. tuning range as it is impacted by tuning step resolution requirements. Frequency deviations can be driven by environmental factors, such as: temperature extremes and rate of change of the temperature on orbit; local magnetic fields; fluctuations in the level of ionizing radiation, and the constant accumulation of radiation dose. Thermal control for the quartz resonator oven achieves small temperature coefficients. Thermal design requires trade-offs between the ideal of thermal isolation from the ambient, and rugged construction. Long term testing of Allan deviation is described, and aging rate results in the low e-l1 range are presented. High resolution test methods and results for radiation sensitivity screening are discussed, with particular reference to low dose testing. Resonator sensitivities in the le-l1 per rad range for a 4 rad/hour exposure have been observed for 4 MHz adhered electrode SC-cut resonators.