BVA resonators: analysis of its low G-sensitivity

The accelerometric and magnetic sensitivities of a quartz resonator are commonly attributed to the design of the resonator, for the main part. Since a few years, it is well-known that G-sensitivity can reach zero if the geometry of the structure (including blank geometry, orientation of the mounting, number of supports, ...) leads to the perfect symmetry around the three axes. In this paper, we show that the BVA resonator has been designed to exhibit a very low G-sensitivity (largely lower than 1*10/sup -10//G). By finite element analysis, we have quantified the influence of some symmetry defects due to manufacturing process (as orientation of the mounting, shift between the vibrating area center and the blank center, ...) on the accelerometric sensitivity with different boundary conditions. Furthermore, we have calculated the frequency shift due to a slight dissymmetry of the mounting structure and deduced how G-sensitivity increases when the inhomogeneity of the stress distribution in the vibrating area increases. At least, we compare these theoretical results to experimental values obtained by two methods: measurements under random vibrations in the range [20-100 Hz], measurement of the frequency shift due to a 2G-tipover test around a given axis.