Theory and Measurement of Backscattering From RFID Tags

This paper presents a method for measuring signal backscattering from RFID tags and for calculating a tag Radar Cross-Section (RCS). The authors derive a theoretical formula for RCS of an RFID tag with a minimum scattering antenna and describe an experimental measurement technique which involves using a network analyzer connected to an anechoic chamber with and without the tag. The return loss measured in this way allows one to calculate the backscattered power and find the tag RCS. Measurements were performed using an RFID tag operating in UHF band. To determine whether the tag was turned on, they used an RFID tag tester. The tag RCS was also calculated theoretically using electromagnetic simulation software.