State of the art radio interrogation system for passive surface acoustic wave sensors

The radio request of passive wireless interrogable surface acoustic wave (SAW) sensors/transponders, is discussed and a radio interrogation system for passive SAW sensors is introduced. The concept is intended to provide an alternative to interrogators with expensive RF and signal processing effects. Consequently the presented system employs a new concept for the generation of the RF signals and for signal windowing. Considering the inherent limitations, the proposed system presents a simple low cost solution for a wide range of various applications. Additionally we have investigated a new, small size and light weight antenna design used in conjunction with the SAW devices to build the passive sensor/transponder. The antenna structure is based on the concept of folded spiral antennas. Details of this proposed multilayered planar antenna design are described and experimental results are discussed. Numerical simulation results compared with experiments are presented. The system shows satisfactory performance and applicability in a wide range of remote monitoring applications.