State of the art in wireless sensing with surface acoustic waves

Surface acoustic wave (SAW) passive devices can be used in novel applications such as wireless identification and sensing. For identification purposes, a SAW transponder picks up an electromagnetic request signal and stores it until all echoes caused by multipath propagation have died away. Then, a characteristic response is beamed back to the receiver. In radio-link sensors, a physical or chemical quantity influences the propagation properties of the SAW and consequently changes the response pattern of the device. This paper surveys the operating principle of such sensors and their state-of-the-art performance. Examples include temperature sensors and sensors for mechatronic applications.