Analysis and design of wideband passive UHF RFID tags using a circuit model

The great majority of commercial UHF RFID tags are based on dipole antennas using a modification of a T-match as a matching circuit. The literature contains examples of wideband matching, but provides little insight as to how wideband behavior is achieved. Here, we present a simple circuit-based theory to describe the antenna, matching circuit, and IC behavior; we present an approach for developing an impeding matching strategy to maximize bandwidth; and we present a concrete example and analysis using a method of moments (MoM) numerical solver. The results show very good agreement with theory.