The effect of substrate and thickness of metallic dot arrays on the detection sensitivity of the traveling wave mode SAW gyroscope

Low sensitivity is the bottleneck problem of the traveling wave mode surface acoustic wave(SAW) gyroscope.In order to improve this problem,a new SAW gyroscope incorporating with metallic dot arrays was developed and its performance was evaluated by experiments.This gyroscope was composed by dual-delay-line oscillators with opposite direction which were fabricated on a same piezoelectric substrate,and copper dot arrays were deposited strategically on the path of the acoustic wave transmission.The approach of analyzing SAW transmission properties in layered structure was used to calculate the SAW gyroscopic effects of devices with different substrate materials and different thickness of copper dot arrays.This laid the foundation of the gyroscope design.Based on the results of theoretical calculation,SAW gyroscopes using 128°YX LiNbO₃ and X-112°Y LiTaO₃ as the substrates were fabricated,its operation frequency was 95 MHz and the thickness of the copper dot arrays adopted were respectively 3000 Å,6000 Å 9000 Å.Single phase unidirectional transducers (SPUDTs) and combed transducers were used to form the SAW device to improve the frequency stability of the oscillators.As a result,a frequency stability of 5 Hz/h was obtained.Performance of the developed SAW gyroscope was tested by accurate rate table.The test results showed that adopting 128°YX LiNbO3 with high electromechanical coupling coefficient and increasing thickness of the metallic dot arrays could all improve the sensitivity of the gyroscope,and the optimized detection sensitivity obtained was 2.7 Hz/(deg/s).