Mutual coupling reduction in linearly polarized compact extended C-shaped chipless RFID tag

Abstract

Compact chipless RFID tags suffer from the mutual coupling between neighboring elements that have close resonant frequencies. In such tags, it is difficult for the words including zero bits to be detected by a reader, leading to false detection. In this paper, two techniques to reduce the mutual coupling effect based on rearrangement of the extended elements with reduced size are proposed. These techniques are applied to a compact chipless RFID tag, which has several nested C-shaped strips placed on both surfaces of the substrate. Top and bottom strips are connected through vias, and slots are placed in the middle of the bottom strips. The resonant frequencies are adjusted by varying the slot lengths in the first technique and variable vias position in the second technique. Through these techniques, the neighboring resonant frequencies can be placed farther apart. In doing so, the stability of the RCS frequency response is improved, which enables a reliable reading where zero bits are coded. For a 9-bit tag, the radius of the substrate is 7.8 mm, equivalent to 0.097λ_g operating over 2-9 GHz. A prototype is fabricated and measured.

KEYWORDS:

• Mutual coupling reduction
• radio frequency identification (RFID)
• chipless RFID tag
• Radar Cross Section (RCS)

Acknowledgments, samples, and data

The data required to replicate the proposed structures and support the conclusions are listed in the Figures and tables.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Fereshteh Salemi

Fereshteh Salemi received the B.Sc. degree in telecommunication engineering from University of Qom, Qom, Iran, in 2014 and the M.Sc. degree in telecommunication engineering from Shahed University, Tehran, Iran, in 2020. Her main research interest includes Chipless RFID tag design.

Hamid Reza Hassani

Hamid Reza Hassani was born in Tehran, Iran. He received the B.Sc. degree in communication engineering from Queen Mary College, London, UK, in 1984, the M.Sc. degrees in microwaves and modern optics from University College, London, in 1985, and the Ph.D. degree in microstrip antennas from the University of Essex, Colchester, UK, in 1990. Currently, he is a Professor with the Electrical and Electronic Engineering Department, Shahed University, Tehran. His research interests include printed circuit antennas, phased array antennas, and numerical methods in electromagnetics.

Sajad Mohammad-Ali-Nezhad

Sajad Mohammad-Ali-Nezhad received the B.Sc. degree in electronic engineering from Shahid Chamran University, Ahwaz, Iran, in 2008, and the M.Sc. and Ph.D. degrees in communication engineering from Shahed University, Tehran, Iran, in 2010 and 2015, respectively. Currently, he is Associate Professor and the Vice President for Administrative and Financial Affairs, University of Qom, Qom, Iran. His research interests include leaky wave antennas, printed circuit antennas, array antennas, phased array antennas, MIMO antennas, RFID tag antennas, frequency selective surface, electromagnetic compatibility, microwave filters, and electromagnetic theory.