Passive Wireless Torque Sensor Based on Surface Transverse Wave

This paper presents a passive wireless torque sensor based on a surface transverse wave (STW). An analysis was conducted on the sensitivity mechanism of STW, and a numerical analysis on the torque sensitivity and temperature coefficient using different cut types was performed. Torque sensitivities with different normalized wavelengths were also analyzed. Numerical calculation results showed that the Y+36° cut quartz was selected to prepare the substrate of the STW torque sensors. Resonators with center frequencies of 435.81 and 438.79 MHz were also prepared and constituted a differential structure as the torque sensing element, with the insertion losses of -11.2 and -9.5 dB and Q of approximately 10 283 and 12 915, respectively. Experimental results indicated that the torque sensitivity of this STW torque sensor was 4.14 kHz/Nm, with a nonlinearity of 0.64%.