This paper aims to disclose the thermal expansion effect on thickness-shear vibrations of quartz filters. To this end, a brand-new “dot-ring” electrode structure was proposed for quartz filter operating in thickness-shear modes (TSMs). Then, a reasonable solution to the government equations of thermal expansion was derived, and the thermal expansion effect on the operation modes and vibration frequencies of the filter were examined in details. Through the rational design of electrode size and quartz plate thickness, a frequency interval was determined with two trapped modes. Under the working temperature between -55°C and 85°C, the electrode sizes changed with the thermal expansion; the resonance frequency declined with the increase of temperature. However, the frequency difference considering the thermal expansion effect is extremely small, indicating that the quartz crystal filter has good thermal stability. The research findings shed new light on the design of quartz filters.
quartz crystals, thickness-shear vibration, filter, thermal expansion effect
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