International Journal on Communications Antenna and Propagation (I.Re.C.A.P.), Vol. 6, N. 6 ISSN 2039 – 5086 December 2016 Copyright © 2016 Praise Worthy Prize S.r.l. - All rights reserved DOI: 10.15866/irecap.v6i6.10462 400 A Novel Electromagnetic Signature Based on RF Identification of Numbers O. Necibi, Ch. Guesmi, S. Naoui, A. Gharsallah Abstract – This paper presents a novel method to identify the numerical digits based on the RF signals. When integrated on dielectric substrate and excited with an electromagnetic wave, every number integrated with metallic strips shows an electromagnetic signature. This signature is unique and characterizes the RCS of the radiating number. Consequently, it could be used for identification purposes. Aafrequencyadomainaapproachawas applied to a set of numbers corresponding to the standard numeration. Simulationaresultsaobtainedawith the electromagnetic simulation software CST-MWS® (Computer Simulation Technology-Microwave-studio) are presented and discussed in this paper. The results of this study confirm that the signatures of each number can establishaanaalgorithm for number recognitionaandaidentificationawithoutaerrors. Copyright © 2016 Praise Worthy Prize S.r.l. - All rights reserved. Keywords: Radio Frequency Identification (RFID), Chipless RFID, Number Identification, RCS, Dipole I. Introduction In recent years, many research efforts have been devoted to develop the chipless RFID TAG [1]-[10]. Besides reducing the cost of tags, chipless devices are fully integrated and can be implemented directly which products. An interesting alternative is to consider the printed information on the product or its packaging as an identifier. This implies that each label (letters, numbers, specific signs ...) is designed to have a unique spectral signature generating a unique ID. Chipless RFID technology is a very recent research axis whose first articles dealing with this subject appeared in 2002 [11] [12], Known by SAW (Surface Acoustic Wave). A complete review and a new classification of chipless RFID tags that can be found on the market and that have been reported to conferences and peer reviews have been presented in [13]. Millimeter wave identification (MMID) was introduced as an update / upgrade of conventional RFID, from the HF and UHF frequency bands to the 30 GHz millimeter wave described in [14]. Pursula et al in [14] justify that the use of higher frequencies has the following advantages: small antenna of the tag, which gives a small label, more compact reading modules [14], and several antenna networks of readers more directives with narrow beams and a higher gain. At 30 GHz, semi- active MMID tags have been successfully designed tested as a proof of MMID tag concept [14]. Theaprevious worka [15] M. Keskilammi et al. have shown that some metal words can beaused to designaanaantenna, so thatait canabe used both for advertising and as radiating element. In this paper, we consider the numbers and we present a method for the RF Identification of numbers. This method exploits the electromagneticasignatures numbers in theafrequencyadomain. The purpose is to demonstrate that the different numbers have different electromagnetic signatures. In fact, the signal’s characteristics in the frequency domain are different, which may be registered in advance and used to identify the correct number. Electromagnetic signatures of 10 numbers are presented and discussed. Thus, a strategy for the classification and identification is performed. Finally theaconclusion and theascope of future work are presented. II. Concept of the Approach Whenaa planeawave encountersaanyaconductive body, theafreeaelectronsabegin to moveawhich results in theagenerationaof surfaceacurrents. The path of the surface current depends on the polarization and on the shape of the object. Dueato theacurrentasurface, the subject begins to radiate electromagnetic waves having specific characteristics. Thus, the object could be seen as aaradiationasource, but the backscattered signal depends only on the lighting signal andamore particularlyaon the RadaraCross Sectiona (RCS) of the conductiveabody. The objective of this study is to analyze the electromagnetic signature of the conductive body, which may be a letter or numeric digit. To finish the application, we limit our study to thearesponseaof theafar fieldaTags. Fig. 1 shows an example of the principle of the analytical method. The metal digit backscattered signal is simulated in