A new low frequency thermally compensated contour mode resonator

A thermally compensated quartz resonator for wrist-watch applications is described. It oscillates at a low frequency (524 kHz) in order to minimize oscillator power consumption. It could be mass-produced by using photolithography and chemical etching. The structure is analyzed and optimized with a contour mode computer program based on variational techniques. The thermal compensation is achieved by the mechanical coupling of two low frequency contour modes of the resonator, namely a flexure-type mode and an extensional-type mode. The structure is such that the elastic part of the mechanical coupling can be balanced with an inertial one for any crystallographic orientation of the substrate. The coupling factor vanishes, but not its thermal derivatives. It is shown that its influence is limited to the second and higher orders of the temperature coefficients of the frequencies