Analysis of backscatter from chipless metal patch RFID using soft computing techniques

The main reasons hindering the wide spread deployment of passive RFID tags are high cost and limited range. The present work focuses on developing a sub-cent RFID capable of operating from a reasonable distance, though with some compromise on the information content. Since there are ample applications of read-only RFID with limited information content, the present technology is expected to fill a substantial part of the niche of sub-cent tags. A metal patch on a metallic ground plane, separated by a dielectric, acts like a microstrip patch antenna and has scattering characteristic defined by poles and zeros depending on the dimensions of the patch. Such resonating structures can be used to create tags, with the purpose of storing information in the various resonant frequencies. Multiple patches, either stacked on top of each other, or located transversely, can be used to increase information content. The challenge is to retrieve these resonant frequencies - from single or multiple patches - in the presence of clutter (unwanted scatter) from surrounding objects. The situation becomes especially difficult in the presence of large metallic objects creating significant amounts of clutter. We have proposed ways to separate resonating part of the signal from clutter, following which soft-computing technique to find exact resonating frequency. Multilayer Perceptron trained with error back propagation could deliver very accurate estimation of the resonant frequencies in real-time. discuss in detail the experimental set-up, data collection and analysis methodology measured at a distance.