Crystal resonator design for space applications

Summary

Crystal resonators may be used on various vehicles. They are submitted to accelerations, shocks, vibrations and to external pressure and temperature variations (acceleration variations may be some 10g, pressure variations may reach one atmosphere and temperature 100°C). The goal of this paper is to describe an attempt to reduce the various environmental effects especially by use of a mounting structure external to the resonator. Each effect needs a particular study. 1) Shocks and vibrations. A particular fixation structure has been designed. Resonators can support a shock equivalent to 1000g over 0.1 ms in any direction. Also the mounting structure resonant frequency can be rejected over 3000 Hz. 2)g sensitivity.g sensitivity has been reduced. Theoretical and experimental results are given. 3) External pressure and temperature variations. Crystal enclosure is submitted to variations of pressure and temperature which yield enclosure deformations. The study of the resonator dependence by respect to its enclosure has been performed. A quartz structure surrounding the vibrating crystal has been designed and specific enclosures have been tried thus yielding reduced mechanical strains due to external pressure and temperature variations. These structures are described and discussed. Based on the results of the previous study of a series of 10 sample resonators has been manufactured. The performances are presented and compared to results obtained with previous designs.