Remote sensing of physical parameters by means of passive surface acoustic wave devices (“ID-TAG”)

A system for remote measurement of numerous physical quantities with passive sensors is presented. It consists of a radio frequency interrogator with evaluation electronics and a surface acoustic wave (SAW) device used as a sensor. For practical tests, an interrogator has been developed, which is able to read commercial identification SAW-tags. As an example, the relative position and temperature of the SAW element have been derived from the received data. The temperature resolution proved to be about 0.1°C within a range of -20°C to +140°C, the distance resolution is about 5 millimeters. The detection distance is up to 15 meters for 5 watts output peak power. The promising results indicate that using this technique remote sensing of many physical parameters is feasible. The sensors are wireless and do not require a power supply, so measurements in dangerous, radioactive or dirty environment or from moving or rotating objects becomes obtainable