SH-SAW transducer analysis on single crystal KNbO3 for liquid sensors

A BEM numerical analysis of IDT structures on Euler angles (0°, 90°, 0°) KNbO₃ has been performed. The analysis considered IDT excitation of both the SH-SAW and SH-BAW modes. The results were targeted at addressing specific issues relevant to liquid sensor applications, such as power partitioning between the SH-SAW and SH-BAW, and SH-BAW power radiation direction into the substrate. The designs with metalized regions outside the IDT seem most promising for liquid sensing applications. Second and third higher order frequency responses for a 5 finger IDT structure showed that 94% and 80%, respectively, of the total input power is converted to the SH-SAW. This result indicates the potential for high frequency applications or sensing platforms that exhibit higher sensitivity at higher operating frequencies. A more rigorous analysis using a combined FEM/BEM tool was also performed, proving there is no need to consider mass loading effects in the analysis of practical IDT structures on the KNbO₃ propagation direction.