Study on the Sensitivity of Diaphragm-Type SAW Pressure Sensor

Pressure sensitivity of the diaphragm-type Surface acoustic wave (SAW) pressure sensor was studied in this work. In the experiment, a one-port SAW resonator was fabricated on a 128° YX-lithium niobate (LiNbO $_{{3}}{)}$ substrate. The SAW resonator was attached to a metal diaphragm to form a pressure sensor. The experimental results showed that both Rayleigh and shear horizontal (SH) waves were excited in the SAW resonator. The pressure sensitivities of Rayleigh and SH waves were measured. It was found that the sensitivity of the SH wave was about 1456 ppm/MPa, which was significantly higher than that of the Rayleigh wave. The result was explained by studying the combined effect of biaxial stress on the strain sensitivity of Rayleigh and SH waves. It was found that the superposition of biaxial stress reduced the pressure sensitivity of the Rayleigh wave, while the superposition of biaxial stress increased the pressure sensitivity of the SH wave. This work provides a guidance for the design of highly sensitive SAW pressure sensors.