Investigation of delay path modifications of Surface Acoustic Wave sensors

Surface Acoustic Wave (SAW) sensors monitor the interaction between a receptor and its target in real time through changes in the properties of the traveling wave (i.e. frequency or phase, and amplitude). A key sensing parameter is power consumption. To increase power transfer we have developed a SAW sensor with microcavities in the delay path on 36° YX LiTaO₃ and 90° ST-X Quartz. Three parameters were identified that determine the effectiveness of microcavities: 1) IDT offset, 2) microcavity depth, and 3) microcavity cross-sectional area. Finite element (FE) simulations were performed using ANSYS to determine the optimum value of each parameter to decrease insertion loss (I.L.). Our results show that the best parameter values are; IDT offset = 10 μm, microcavity depth = 2.5 μm and microcavity cross-sectional area = 10 μm × 10 μm, for a device with center frequency of about 100 MHz.