Degradation of Liquid-Phase Shear Horizontal Surface Acoustic Wave Sensor Owing to Lack of Energy Concentration of Surface and a Compensation Method

摘要

In this paper we describe liquid-phase two-channel shear horizontal surface acoustic wave (SH-SAW) delay-line sensor devices on 36° Y-X LiTaO_3 substrates. One delay line has a metallized propagation area and the other has an unmetallized propagation area. The permittivity and conductivity of the liquids can be calculated from the velocity changes and attenuation changes of the SH-SAWs in the two delay-lines. However, in the case of the low-permittivity liquids, the SH-SAWs in the delay line with an unmetallized propagation area can be degraded owing to the lack of SH-SAW energy concentration of the surface. Thus the obtained permittivity and conductivity of the liquids were slightly different from the exact values. In this paper, the drawback of the liquid-phase SH-SAW sensors is described, and in order to overcome this drawback, a compensation method is presented.