Optimization of Quartz SAW Resonator Structure with Groove Gratings

Abstract

Abstruct-A new surface acoustic wave (SAW) resonator optimum design method is proposed to reduce resonator sue. The fundamental design feature is optimization of the interdigital transducer (IDT) electrode period to reflector electrode period ratio, in order to adjust the frequency for the maximum IDT admittance to the maximum reflector reflection point. As a result of the optimized electrode period ratio, both reflector and IDT frequency responses are utilized to advantage, and good resonant Characteristics are obtained with a reduced number of reflector electrode fingers. This design method can be effectively applied for SAW resonators with groove gratings, both on reflectors and transducer, that are formed by a reactive sputter etching process. 145 MHz SAW resonators with groove gratings fabricated on a small 6 mm X 3 mm ST-cut quartz chip have provided good electrical performances, such as high Q values above 2 X lo4 and low resonance resistance in the 20-30 range.