Design and simulation of SAW sensors for wireless sensing

This paper presents the design and frequency response simulation of Surface Acoustic Wave (SAW) devices using MATLAB(TM) used for passive wireless sensing of various measurands. Since SAW devices are widely used in radio frequency sensing applications, it is desirable to evaluate the device prior to fabrication especially in cases where the device material and dimensions have a major influence on the performance of the overall system. Three different types of SA W configurations namely the delay line, one-port resonator and two-port resonator was simulated in MATLAB(TM) Both the equivalent circuit and the transmission matrices approaches have been used to simulate the frequency response of these SAW devices. The measured and simulated frequency responses are compared for a 433.92 MHz one-port resonator and it appears that the equivalent circuit approach is good for near resonance simulation whereas transmission matrix approach is a better choice if the response over a wide frequency range is required. Also, the effect of Inter-digital Transducer (IDT) lead resistance, acoustic aperture and number of finger pairs on the performance of the system was studied and it was observed that an increase in the acoustic aperture and number of finger pairs increases the gain of the SAW device vice whereas an increase in the lead resistance lowers the gain. The results obtained are presented here along with the design parameters used in the simulations.