Design and Analysis of a Novel Wireless Passive Microsensor Based on the SAW Theory

A novel wireless passive SAW microsensor is designed, based on the delay line theory and the coupling-of-modes (COM) theory. For this purpose, a P-matrix with new expression is derived utilizing the COM theory. The applicability and accuracy of the new P-matrix model in analyzing the unitary symmetry IDT and the reflector have been validated. The effect of the temperature is included in the pressure feedback signal and a weighted factor is introduced in order to separate the temperature effect from the feedback signal. Therefore, the temperature and pressure can be accurately measured at the same time. In this sensor design, the energy converted from IDT is fully used, and the interference between the signals is minimized. The IDT and its reflectors have been optimally designed to improve the sensitivity of the sensor. This wireless passive sensor is capable of working under various conditions.