Wireless interrogator system for SAW-identification-marks and SAW-sensor components

A sensor system is presented, comprising surface acoustic wave (SAW) components as identification marks ("ID-tags") or as sensor elements for various tasks, and an interrogator for reading the sensor elements from a distance. As interrogator a chirp radar device at 2.45 GHz center frequency was developed, using a pair of dispersive SAW filters for pulse expansion and compression. It transmits expanded pulse signals to the SAW sensor elements and receives their responses. Reading ID-tags at a maximum distance of about 2.5 m with 10 mW peak output power, this system was successfully introduced to the Munich subway system for railway vehicle identification at high speed.