Comparative study of SAW temperature sensor based on different piezoelectric materials and crystal cuts for passive wireless measurement

As widely reported substrates for surface acoustic wave (SAW) temperature sensors, YX-cut quartz, YZ-cut LiNbO₃ and 128°YX-cut LiNbO₃ are selected to fabricate different one-port SAW resonator temperature sensors and comprehensive comparative studies of their performance and specifications are conducted carefully in this paper. Firstly, SAW sensors of each cut with 50 different layouts were designed and fabricated according to the calculated SAW velocity, and a general wireless measurement platform was setup. Secondly, under the same test conditions, Q factor, temperature sensitivity and decaying waves of these sensors were tested, and along with the calculated temperature coefficient of frequency (TCF), these parameters were finally compared respectively. After comparison, the conclusions are as follows: LiNbO₃ sensors had higher temperature sensitivity, and showed superiority without the limitation of distance in wireless measurements, while quartz sensors performed well when the distance increased, and this suggests they can be applied to long distance sensing for their high Q factor even the sensitivity is moderate.