State of the art in signal processing for wireless SAW sensing

Wireless measurement systems with passive SAW sensors offer the new and exciting perspectives for remote monitoring of rotating parts, or in harsh environments. This paper concentrates on the signal processing required for those sensor systems with regard to the sensors, the system hardware and the radio transmission. Different directly effected delay lines, impedance loaded devices and resonators have been used as SAW sensors. Wideband time domain interrogation and narrowband frequency domain interrogation have been investigated theoretically and experimentally in combination with the radio channel and the evaluation method. We focus on the occurring errors and the origins of these effects. Actual estimations for the different errors are given. We achieved a resolution of 10/sup -5/ to 10/sup -6/. The measurement's bandwidth is up to 10 kHz for conventional sensors and up to a few hundreds of kHz for the new transponder type. A read out distance without averaging of several meters is achieved.