SAW sensors have been used in both wired and wireless configurations to measure physical properties such as temperature, pressure, strain, and torque. Recently, wireless SAW sensors for physical parameters have been combined with RFID coding, to produce sets of individually identifiable wireless sensors.
The most common wireless SAW sensor type is the temperature sensor , and other sensors are possible using similar techniques. Frequency modulated continuous wave (FMCW) interrogation systems have been used commercially for temperature sensors on 128 lithium niobate (as in the Baumer-Ident module discussed by Reindl ) with pulse position modulation coding enabling 104 codes. In this system, a rough measurement of temperature is obtained by evaluating gross delay, and a finer temperature measurement is obtained by using the gross measurement to eliminate the phase ambiguity of 2 i and subsequently utilizing phase to calculate temperature with a resolution of ±2°C . This approach is extended by Kuypers  to achieve accuracies of approximately ±0.1°C.
A wide range of additional work has been done in the area of passive wireless SAW sensor and sensor/tag devices, including [3-5]. Reference  provides an analysis of the performance achievable using several of the aforementioned algorithms. A small sampling of relevant patents are given in references [7-10]. ASR&D has extended the state of the art in SAW physical sensors to include innovative new acoustic wave device structures with design specified sensitivity. More detail on this work can be found on our Physical Sensor research page.
- L. Reindl and I Shrena, “Wireless Measurement of Temperature using Surface Acoustic Waves Sensors”, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 51, No. 11, November 2004, pp. 1457-1463.
- J. Kuypers et. al., “2.45 GHz Passive Wireless Temperature Monitoring System Featuring Parallel Sensor Interrogation and Resolution Evaluation”, IEEE Sensors 2006, EXCO, Daegu, Korea, October 2006, pp. 773-776.
- L. Reindl et. al., “Theory and Application of Passive SAW Radio Transponders as Sensors”, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 45, No. 5, September 1998, pp. 1281-1292.
- F. Schmidt et. al., “Remote Sensing of Physical Parameters by means of Passive Surface Acoustic Wave devices (“ID-Tag”)”, Proceedings of the 1993 IEEE Ultrasonics Symposium, p. 589-592.
- W. Buff et. al., “Remote Sensor System using Passive SAW sensors”, Proceedings of the 1994 IEEE Ultrasonics Symposium, p. 585-588.
- S. Schuster et. al., “Performance Evaluation of Algorithms for SAW-based Temperature Measurement”, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 53, No. 6, June 2006, pp. 1177-1185.
- C. S. Hartmann et. al., US 6,708,881 B2 “Reader for a high information capacity SAW Identification Tag and method of use thereof”, Mar. 23, 2004.
- C. S. Hartmann et. al., US 6,966,493 B2 “Surface acoustic wave identification tag having enhanced data content and methods of operation and manufacture thereof”, Nov. 22, 2005.
- C. S. Hartmann et. al., US 7,264,149 B2 “SAW Identification Tag Discrimination Methods”, Sep. 4, 2007.
- L. Reindl et. al., US 6,455,979 B2 “Surface acoustic wave component which can be interrogated by radio and has an optimum code size”, Sep. 24, 2002.