Passive remote sensing for temperature and pressure using SAW resonator devices

Wireless sensing using passive sensors based on surface acoustic wave (SAW) technology is necessary for many applications. In this paper a new sensor design that uses the differential frequency output from two SAW resonators (SAWR) for temperature and pressure measurement is presented. The sensor, which consists of two SAWRs on the same substrate with different SAW propagation directions, relies on the variations of the SAW propagation velocity to measure environmental quantities such as pressure or temperature. The aim of this approach is to suppress the disturbing influences of the RF link (radio channel) between the interrogation unit and the passive sensor device. In this case, the output signal is a frequency difference and does not depend on changes in the radio channel during the transmission of the sensor signal.