{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,20]],"date-time":"2026-01-20T10:08:55Z","timestamp":1768903735786,"version":"3.49.0"},"reference-count":34,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2019,11,3]],"date-time":"2019-11-03T00:00:00Z","timestamp":1572739200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100011665","name":"Deanship of Scientific Research, King Saud University","doi-asserted-by":"publisher","award":["KEP-Msc-6-135-39"],"award-info":[{"award-number":["KEP-Msc-6-135-39"]}],"id":[{"id":"10.13039\/501100011665","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This work presents a novel technique for designing chipless radio frequency identification (RFID) tags which, unlike the traditional tags with complex geometries, are both compact and printable. The tags themselves are alphabets, which offers the advantage of efficient visual recognition of the transmitted data in real-time via radio frequency (RF) waves. In this study, the alphabets (e.g., a, b and c) are realized by using copper etching on a thin dielectric substrate (TLX-8) backed by a ground plane. It is shown that the original signature of the frequency response of the backscattered radar cross-section (RCS) of the letter, displays dips that are unique to the individual letters. The tags have been simulated, fabricated and their monostatic cross-sections have been measured by using a dual-polarized Vivaldi antenna in the frequency band ranging from 6 to 13 GHz. The study also includes, for the first time, a detailed analysis of the impact of changing the shape of the tag owing to variation in the font type, size, spacing, and orientation. The proposed letters of the alphabet are easily printable on the tag and provide an efficient way to visually recognized them and, hence, to detect them in a robust way, even with a low coding density of 2.63 bit\/cm2. The advantages of the proposed novel identification method, i.e., utilization of the both co- and cross-polar RCS characteristics for the printable clipless RFID tags are the enhancement of the coding density, security and better detection of the alphabet tags with different fonts by capturing the tag characteristics with better signal to noise ratio (SNR). Good agreement has been achieved between the measured and simulated results for both co- and cross-polarized cases.<\/jats:p>","DOI":"10.3390\/s19214785","type":"journal-article","created":{"date-parts":[[2019,11,4]],"date-time":"2019-11-04T04:13:08Z","timestamp":1572840788000},"page":"4785","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Robust Detection for Chipless RFID Tags Based on Compact Printable Alphabets"],"prefix":"10.3390","volume":"19","author":[{"given":"Hatem","family":"Rmili","sequence":"first","affiliation":[{"name":"Electrical and Computer Engineering, Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Boularess","family":"Oussama","sequence":"additional","affiliation":[{"name":"Communications Systems Laboratory, National Engineering School of Tunis, University of Tunis El Manar, BP 37, Belvedere 1002 Tunis, Tunisia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jawad","family":"Yousaf","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, Abu Dhabi University, 1970 Abu Dhabi, UAE"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bandar","family":"Hakim","sequence":"additional","affiliation":[{"name":"Electrical and Computer Engineering, Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Raj","family":"Mittra","sequence":"additional","affiliation":[{"name":"Electrical and Computer Engineering, Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia"},{"name":"EMC Lab, Electrical and Computer Engineering Department, University of Central Florida, Orlando, FL 32816, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Taoufik","family":"Aguili","sequence":"additional","affiliation":[{"name":"Communications Systems Laboratory, National Engineering School of Tunis, University of Tunis El Manar, BP 37, Belvedere 1002 Tunis, Tunisia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Smail","family":"Tedjini","sequence":"additional","affiliation":[{"name":"LCIS, University Grenoble-Alpes, 26902 Valence, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"78007","DOI":"10.1109\/ACCESS.2018.2884651","article-title":"Document Verification: A Cloud-Based Computing Pattern Recognition Approach to Chipless RFID","volume":"6","author":"Arjomandi","year":"2018","journal-title":"IEEE Access."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1017\/wpt.2015.16","article-title":"Analysis of electromagnetic signature of Arabic alphabet as RF elementary coding particles","volume":"2","author":"Boularess","year":"2015","journal-title":"Wirel. Power Transf."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1002\/mop.29493","article-title":"Design of a chipless RFID tags based on natural fractal geometries for security applications","volume":"58","author":"Rmili","year":"2016","journal-title":"Microw. Opt. Technol. Lett."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"3785","DOI":"10.1109\/TMTT.2015.2482968","article-title":"Compact Printable Chipless RFID Systems","volume":"63","author":"Islam","year":"2015","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1542520","DOI":"10.1155\/2018\/1542520","article-title":"A High-Density L-Shaped Backscattering Chipless Tag for RFID Bistatic Systems","volume":"2018","author":"Issa","year":"2018","journal-title":"Int. J. Antennas Propag."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Andriamiharivolamena, T., Vena, A., Perret, E., Lema\u00eetre-Auger, P., and Tedjini, S. (2014, January 8\u20139). Chipless identification applied to human body. Proceedings of the IEEE RFID Technology and Applications Conference (RFID-TA), Tampere, Finland.","DOI":"10.1109\/RFID-TA.2014.6934236"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1109\/LMWC.2009.2024840","article-title":"Phase-Encoded Chipless RFID Transponder for Large-Scale Low-Cost Applications","volume":"19","author":"Balbin","year":"2009","journal-title":"IEEE Microw. Wirel. Compon. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1411","DOI":"10.1109\/TMTT.2009.2017323","article-title":"Multiresonator-Based Chipless RFID System for Low-Cost Item Tracking","volume":"57","author":"Preradovic","year":"2009","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_9","unstructured":"McVay, J., Hoorfar, A., and Engheta, N. (2006, January 17\u201319). Space-filling curve RFID tags. Proceedings of the IEEE Radio and Wireless Symposium, San Diego, CA, USA."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"654","DOI":"10.1109\/TUFFC.2010.1462","article-title":"Review on SAW RFID tags","volume":"57","author":"Plessky","year":"2010","journal-title":"IEEE Trans. Ultrason. Ferroelectr. Freq. Control"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Herrojo, C., Moras, M., Paredes, F., N\u00fa\u00f1ez, A., Ramon, E., Mata-Contreras, J., and Mart\u00edn, F. (2018). Very Low-Cost 80-Bit Chipless-RFID Tags Inkjet Printed on Ordinary Paper. Technology, 6.","DOI":"10.3390\/technologies6020052"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Karmakar, N.C., Zomorrodi, M., and Divarathne, C. (2016). Advanced Chipless RFID: MIMO-Based Imaging at 60 GHz-ML Detection, John Wiley & Sons.","DOI":"10.1002\/9781119227342"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Necibi, O., Beldi, S., and Gharsallah, A.O.N. (2015, January 21\u201323). Design of a chipless RFID tag using cascaded and parallel spiral resonators at 30 GHz. Proceedings of the 2nd World Symposium on Web Applications and Networking (WSWAN), Sousse, Tunisia.","DOI":"10.1109\/WSWAN.2015.7210327"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Singh, T., Tedjini, S., Perret, E., and Vena, A. (2011, January 12\u201314). A frequency signature based method for the RF identification of letters. Proceedings of the IEEE International Conference on RFID, Orlando, FL, USA.","DOI":"10.1109\/RFID.2011.5764628"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1325","DOI":"10.1049\/iet-map.2016.0759","article-title":"Hybrid coding chipless tag based on impedance loading","volume":"11","author":"Ni","year":"2017","journal-title":"IET Microw. Antennas Propag."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1109\/MMM.2016.2549160","article-title":"Tag, You\u2019re It Radar Cross Section of Chipless RFID Tags","volume":"17","author":"Karmaker","year":"2016","journal-title":"IEEE Microw. Mag."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3356","DOI":"10.1109\/TMTT.2011.2171001","article-title":"Chipless RFID Tag Using Hybrid Coding Technique","volume":"59","author":"Vena","year":"2011","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_18","unstructured":"Grishin, A.M., and Mays, R.M. (2007). Microwave Readable Dielectric Barcode. (No. 7,205,774), U.S. Patent."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Mukherjee, S., and Chakraborty, G. (2009, January 14\u201316). Chipless RFID using stacked multilayer patches. Proceedings of the Applied Electromagnetics Conference (AEMC), Kolkata, India.","DOI":"10.1109\/AEMC.2009.5430585"},{"key":"ref_20","unstructured":"Vena, A., Perret, E., and Tedjini, S. (2016). Chipless RFID Based on RF Encoding Particle: Realization, Coding and Reading System, Elsevier."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Demir, M.A., and Mutlu, F. (2018, January 10\u201314). Design of Highly Distinguishable Letters for Inkjet-Printed Chipless RFID Tags. Proceedings of the IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC), Cartagena des Indias, Colombia.","DOI":"10.1109\/APWC.2018.8503666"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1109\/LMWC.2012.2188785","article-title":"A Fully Printable Chipless RFID Tag With Detuning Correction Technique","volume":"22","author":"Vena","year":"2012","journal-title":"IEEE Microw. Wirel. Compon. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"4008","DOI":"10.1109\/TMTT.2013.2282280","article-title":"Chipless RFID Tag Localization","volume":"61","author":"Anee","year":"2013","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2326","DOI":"10.1109\/TMTT.2016.2568180","article-title":"Temporal Separation Detection for Chipless Depolarizing Frequency-Coded RFID","volume":"64","author":"Ramos","year":"2016","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"372","DOI":"10.1109\/LAWP.2004.841212","article-title":"Using text as a meander line for RFID transponder antennas","volume":"3","author":"Keskilammi","year":"2004","journal-title":"IEEE Antennas Wirel. Propag. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Tedjini, S., Boularess, O., Andriamiharivolamena, T., Rmili, H., and Aguili, T. (2017, January 4\u20139). A novel design of chipless RFID tags based on alphabets. Proceedings of the IEEE MTT-S International Microwave Symposium (IMS), Honololu, HI, USA.","DOI":"10.1109\/MWSYM.2017.8058929"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Vena, A., Singh, T., Tedjini, S., and Perret, E. (2011, January 13\u201320). Metallic letter identification based on radar approach. Proceedings of the XXXth URSI General Assembly and Scientific Symposium, Istanbul, Turkey.","DOI":"10.1109\/URSIGASS.2011.6050583"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"4509","DOI":"10.1109\/TAP.2012.2207347","article-title":"High-Capacity Chipless RFID Tag Insensitive to the Polarization","volume":"60","author":"Vena","year":"2012","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Necibi, O., Naoui, S., and Gharsallah, A. (2016, January 21\u201323). Design of a chipless RFID TAG based on the frequency shift technique for K band. Proceedings of the 2nd International Conference on Advanced Technologies for Signal and Image Processing (ATSIP), Monastir, Tunisia.","DOI":"10.1109\/ATSIP.2016.7523194"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1733","DOI":"10.1049\/iet-map.2015.0281","article-title":"Radar cross-section measurement in millimetre-wave for passive millimetre-wave identification tags","volume":"9","author":"Hotte","year":"2015","journal-title":"IET Microw. Antennas Propag."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Jing, C., Sun, T., Chen, Q., Du, M., Wang, M., Wang, S., and Wang, J. (2019). A Robust Noise Mitigation Method for the Mobile RFID Location in Built Environment. Sensors, 19.","DOI":"10.3390\/s19092143"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Manekiya, M., Donelli, M., Kumar, A., and Menon, K.S. (2018). A Novel Detection Technique for a Chipless RFID System Using Quantile Regression. Electronics, 7.","DOI":"10.3390\/electronics7120409"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Khadka, G., and Hwang, S.-S. (2017). Tag-to-Tag Interference Suppression Technique Based on Time Division for RFID. Sensors, 17.","DOI":"10.3390\/s17010078"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1109\/TAP.2007.915423","article-title":"Gains For RF Tags Using Multiple Antennas","volume":"56","author":"Griffin","year":"2008","journal-title":"IEEE Trans. Antennas Propag."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/21\/4785\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:31:39Z","timestamp":1760189499000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/21\/4785"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,11,3]]},"references-count":34,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2019,11]]}},"alternative-id":["s19214785"],"URL":"https:\/\/doi.org\/10.3390\/s19214785","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,11,3]]}}}