Abstract
Propagation characteristics of a surface acoustic wave on a piezoelectric substrate depend on an adjacent medium. When the SAW is applied for a signal processing application of mobile communication systems, it is important to reduce the changes of the propagation characteristics. For a SAW sensor application, the changes are detected to determine physical and chemical properties of the medium. Gas- and liquid-phase sensors are realized by using the SAW device. Sensor sensitivities depend on the used piezoelectric materials. In this paper, first, we describe acoustic wave sensors. Then the detection mechanism and perturbation theories of the SAW sensors are explained. The sensor sensitivity is calculated by using the perturbation equations. Typical measurement systems are also explained. Moreover, several applications of the SAW sensors, such as results of gas sensors, liquid measurements, and immunoreaction measurements, are described.
