Angle-Based Chipless RFID Tag With High Capacity and Insensitivity to Polarization

This paper presents a novel angle-based chipless radio frequency identification (RFID) tag with high capacity that is polarization-independent. Its scatterer is designed to be V-shaped. It encodes data using the space angle between two arms of the V-shape and is identified by measuring the scattered field in two orthogonal polarization directions. Even if it is tilted, the tag can be identified. The advantage of angle-based tag is that every element can encode three-bit data. This is helpful to get higher capacity. Also, for different codes of one element, the proposed tag uses the same spectrum. This is beneficial to improve the efficiency of the spectrum. First, the tag using the uniform impedance resonator (UIR) is designed. Then, the UIR chipless tag is reformed as stepped impedance resonator (SIR) tag to suppress the second harmonic. The realized tags operate in the frequency range 1.83-2.15 GHz and the identification errors are less than 3.9°. Every element of the realized tags can carry 3 bits of coding information.