Passive radio-requestable SAW multisensor system

For some years, SAW devices are applied to complete passive and wireless interrogating systems as ID tags and as physical or chemical sensors for remote monitoring. We report on a wireless remote requestable SAW multisensor system developed with some single identification sensor elements e.g. for window-glass breakage monitoring. The identification single sensors are realized by reflective delay lines. They are operated in the frequency range of 825 to 875 MHz on 128°YX-LiNbO₃ and on 36°YX-LiTaO₃ substrates. For an optimized sensor element operation different SAW structures have been designed and tested. The multisensor system is able to interrogate single remote sensors in a range of more than 4 meters. The radio transceiver station, radiating a maximum output power of 500 mW, evaluates radio signals up to -85 dBm.