Analysis on Polarization Responses of Resonators for Frequency-Coded Chipless RFID Tags

This article presents a method to analyze co- and cross-polarized responses of the resonators exploited in the development of frequency-coded chipless radio frequency identification (RFID) tags. The method uses the complex radar cross Section (RCS) matrix to characterize the polarization of the scattered response of resonators. Four different symmetry states are introduced, and all resonators are classified under each category based on their structures. Then, the complex RCS matrix is obtained for each group. Then, four different resonators, each representing the respective symmetry state, are simulated and measured to validate the theory. To highlight the advantages of the presented method, two significant applications of the method are investigated. The presented theory is used in the first application to determine resonator structures for designing orientation independent cross-polarized tags. The proposed technique not only accelerates the design of frequency-coded chipless RFID tags but also helps figure out proper geometry for resonators with cross-polarized responses with minimum amplitude deviation at different azimuth plane orientation angles. In the latter application, we predict co- and cross-polarized responses of a tag at arbitrary orientation angles, using one initial measurement. This prediction provides a thorough insight into the co- and cross-polarized responses of tags at different orientation angles.