4.74-GHz Harmonically Operated SAW Temperature and Strain Sensors

This paper presents the development of surface acoustic wave (SAW) temperature and strain sensors that can operate at high frequencies up to 4.74 GHz. The third harmonic response of the SAW device was utilized to enable operation at higher frequencies, which helped overcome the limitations of the contact photolithography process used in fabrication. Specifically, a design of an orthogonal frequency coding (OFC) SAW device provided by Pegasense LLC and originally designed for use with lithium niobate YZ was implemented on lithium niobate YX 128 cut, which increased the device’s operating frequency from 4.3 GHz to 4.74 GHz. The SAW device demonstrated wireless temperature sensing capabilities with a standard deviation of 0.044C after signal processing using a thousand averages and a matched filter. Additionally, initial measurements of a strain sensor at 4.74 GHz showed good correlation with commercial strain sensor measurements, with a standard deviation of $2.278\mu $ strains using 1000 averages and a frequency sensitivity of $- 1.260\mu $ strains approximately. The potential of SAW technology to impact super high frequencies (SHF) and its practical application in wireless temperature and strain sensing will be highlighted.