A comparison of two ways to reducing the mutual coupling of chipless RFID tag scatterers

This paper presents two ways to reduce the mutual coupling between the resonators of the RFID chipless tags. This reduction significantly improves the uniformity of the RCS response of the tag over the operational frequency range from 2 to 4 GHz. The first modification to the tag layout is based on an inter-element rearrangement of the array elements. The second layout modification is based on narrowing the strip width and tapering the longitudinal dipole arms toward the open end. Significantly improved homogeneity of the RCS response in comparison with the original array of folded dipole scatterers was confirmed by simulation and by measurements of 20-bit chipless RFID transponders. The second modification further improves the frequency resolution, which may consequently provide higher encoding capacity in a unit area, but at the expense of a decreased RCS response.