P1I-9 Passive 2.45 GHz TDMA based Multi-Sensor Wireless Temperature Monitoring System: Results and Design Considerations

This paper presents a TDMA (time division multiple access) based wireless temperature monitoring system using 2.45 GHz passive surface acoustic wave (SAW) delay line sensors. A three-step resolution refinement scheme using a combined delay and phase evaluation is proposed. Using a transmission power of 2 dBm (1.59 mW) a temperature accuracy of 0.19 K and 0.1 K(6sigma), were achieved for an interrogation distance of 1.4 m, and 1.3 m, respectively. The sensor design is discussed using experimental results concerning the relationship between the SNR (signal to noise ratio) of the sensors and the accuracy in time delay or phase measurement. Also, the direct electron beam writing on chemically-reduced (black) LiNbO
₃
is described