Design of Passive Wireless resonance type SAW Temperature Sensor

In recent years, the growing demand for temperature monitoring has become more and more urgent. Temperature monitoring technologies have been greatly developed. There are now a variety of monitoring techniques, but there also exist their own shortcomings: (1) Normal temperature monitoring; its insulating performance cannot be guaranteed. (2) Infrared temperature monitoring; the veracity of temperature data received cannot be guaranteed. (3) Optical fiber temperature monitoring; the cost is high. (4) Active wireless temperature monitoring; it is difficult to maintain. SAW Sensor has been widely used in passive wireless measuring field due to its advantages that includes being small in volume, high precision measurement and ability to work in the special environment of high-voltage, high-temperature and no power supply. On the basis of issues of parameter monitoring in the untouchable environment and in accordance with INTELLISAW reader´s product standards, this paper has designed a Passive Wireless resonance type SAW Temperature Sensor by analyzing resonance type SAW Temperature Sensor, IDT, reflectors principle and calculating their parameters. As to piezoelectric substrate material, this paper has chosen quartz XY because of its advantages of high temperature sensitivity, stable temperature characteristics, wide temperature measuring range, large electromechanical coupling coefficient, high conversion efficiency, good consistency and repeatability, ease of processing, low cost and so on. In the SAW sensor designed in this paper, temperature monitoring range is between -25°C and 125°C, a reader can read 12 sensors signals in the meantime. By studying on the equivalent circuit model of the Sensor and on the basis of resonance condition, this paper has calculated series resonance frequency and parallel resonance frequency of SAW, the results demonstrated that the frequency range designed by this paper can be applied to INTELLISAW.