压电基片与金属点阵厚度对行波模式声表面波陀螺仪检测灵敏度的影响

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

过低的灵敏度性能一直是声表面波(SAW)陀螺仪的瓶颈问题,对此,提出了一种结合金属点阵用以改善陀螺效应的新型行波模式SAW陀螺仪,并对其性能进行了评价。该结构由双延迟线型振荡器构成,两延迟线平行且反向制作于同一压电基片上,在延迟线的声传播路径上分布铜点阵。结合层状介质中声波传输特性的研究方法分析了两种压电晶体材料、不同金属点阵膜厚对传感器响应的影响,从而为确定陀螺仪的设计奠定理论基础。基于理论计算结果,研制了以128°YX LiNbO3及X-112°Y LiTaO_3为压电基片,铜点阵厚度分别为3000 A,6000 A,9000 A的95 MHz声表面波陀螺仪。为改善振荡器的频率稳定性,延迟线采用了具有梳状结构的单相单向换能器结构。振荡器的测试频率稳定度达到了±5 Hz/h。利用精确速率转台对所研制的SAW陀螺仪性能进行了测试。测试结果表明:采用机电耦合系数较高的128°YX LiNbO_3基片并增加金属点阵厚度均能有效提高陀螺仪的检测灵敏度,所获得的最大检测灵敏度为2.7 Hz/(deg/s)。

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 A, 6000 A 9000 A. 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）.