Enhanced sensitivity of wireless and passive SAW based strain sensor with a differential structure

A new configuration is proposed to improve the sensitivity and temperature stability of the surface acoustic wave (SAW) strain sensor by using a differential dual-chip structure. Each SAW chip with a one-port resonator pattern is prepared by depositing Al interdigital transducers (IDTS) on Y-cut quartz crystal using the photolithographic technique, and positioned orthogonally in the ceramic package. The opposite polarity of the strain sensitivity arises from the directivity of the strain tensor, and enhanced sensitivity will be expected by differencing the response from each sensing chip. Referring to the perturbation theory and finite element modeling (FEM), the sensitivity of the proposed sensor configuration is simulated and predicted, and confirmed by the wirelessly characterization. Excellent temperature compensation at 0 – 120 °C, higher sensitivity of 1.3 kHz/μe, and satisfied linearity in a detection range of ±500 μe are achieved, and estimated detection limit reaches ±0.7 μe.