Development of New Wireless Surface Acoustic Wave Sensor for Simultaneous Detection of Pressure–Temperature and Identification Tag

概要

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A 440 MHz wireless surface acoustic wave (SAW)-based pressure sensor, integrated with a temperature sensor and an identification (ID) tag, has been developed on a 41° YX LiNbO3 piezoelectric substrate. Two substrates with reflective delay line patterns were bonded together, forming a sealed inner space to provide a reference pressure. The pressure sensor was placed on the top substrate, whereas the ID tag and the temperature sensor were located on the bottom substrate. The finite element method (FEM) and coupling of modes (COM) modeling were used to determine the optimal design parameters. Using the network analyzer as the reader unit, the fabricated sensor was wirelessly characterized. Sharp reflection peaks with high signal to noise (S/N) ratios and few spurious peaks were observed using the network analyzer. Depending on the external pressure values, the phase shifts of the reflection peaks were linearly varied. The evaluated pressure sensitivity was approximately 2.96°/kPa. Eight sharp reflection peaks were observed for the ID tag. The temperature sensor was also characterized in the range of 20–200 °C. The obtained sensitivity was ${\sim}10.6$°/°C.
2009-06-25