Passive wireless SAWR sensor system model including the effects of antenna distances

Many models are used to simulate passive wireless SAWR sensors. The simulations show the mechanical work of SAW and the match between the connect cable and SAW resonators. There is little discussion about the effects of antennas and RF distances. An improved model was presented in the paper. It consisted of SAWR, matching networks, and antenna array models. The electrical properties of single-port SAW resonators are depicted by their equivalent circuit. The classical configurations are applied for the design of matching network. The antenna array formed by two antennas is simulated by a two-port network model. Cascading these models, an improved model was formed. It was the first time that the two-port model of antenna array was applied for the simulation of passive wireless SAWR sensors. Some simulations were performed. The results showed that the mutual-impedance of antenna array changing with the antenna distances was the mechanical effect. Then a matching network with excellent stability was designed. An experiment system was established and the sensitivity about −1.75 ppm/cm was obtained in the readout range of 1–20 cm.