RF and THz Identification Using a New Generation of Chipless RFID Tags

This article presents two chipless RFID approaches where data are reading using electromagnetic waves and where the medium encoding the data is completely passive. The former approach rests on the use of RF waves (more precisely the ultra-wide band UWB). The tags developed for this application are comparable with very specific, planar, conductive, radar targets where the relation between the tag geometry and its electromagnetic signature is perfectly known and is used to encode the data. The principle of operation as well as the realization process of the RF tags presented in this paper is similar to those already reported in the literature. However, contrary to the majority of chipless RFID tags, these labels do not present an antenna function dissociated from the circuit part where the data are stored. Here, functions such as the receiver, the treatment and the emitter of the signal are closely dependent. The data storage capacity of the RF chipless tags is proportional to of the used frequency bandwidth. As radio spectrum is regulated, the number of possible encoding bits is thus strongly limited with this technology. This is the reason why we introduce a new family of tags radically different from the preceding one, where data is encoded in volume thanks to a multilayer structure operating in the THz domain. These two approaches although different are complementary and allow to increase significantly the data storage capacity of the chipless tags. Simulation and experimental results are reported in this paper for both configurations. We demonstrate a coding capacity of 3.3 bit/cm2 for RFID chipless tags and a potential 10 bits coding capacity in the THz domain

Desenvolvimento de sistema de radiofrequência para identificação de cédulas monetárias e documentos

Orientador: Hugo Enrique Hernández-FigueroaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Este trabalho descreve o desenvolvimento de um sistema de radiofrequência, eficaz e de baixo custo, para identificação de cédulas monetárias e documentos com a intenção de evitar falsificações. O sistema proposto é baseado nas tecnologias de linha de microfita e RFID sem chip, porém, a identificação é feita através do contato do objeto com a leitora. Para que essa identificação ocorra, na leitora, ressoadores em formato espiral são dispostos próximos a uma linha de transmissão, cada ressoador representando um bit de dado, e ressoam livremente até que uma cédula ou documento seja colocada em contato e devidamente alinhada. Cada cédula ou documento deve possuir uma marca metálica impressa em camada interna, pois dificulta falsificações e as ondas eletromagnéticas conseguem atravessar o papel, de forma que cada marca defina o código binário de cada objeto, uma vez que essas marcas metálicas suprimem as ressonâncias dos ressoadores situados na leitora. Em outras palavras, as marcas metálicas transformam o estado do bit de dado, bit 0 ou 1, correspondendo aos estados de presença e ausência de ressonância, respectivamente. O sistema também tem potencial para aumento do volume de codificação de dados com a possibilidade do sistema ternário, quando as ressonâncias possuem três estados. Resultados de simulações e resultados de medições também são apresentados neste trabalhoAbstract: This work describes the development of a low-cost and efficient radiofrequency system for banknotes and documents identification intending to avoid counterfeiting. The proposed system is based on the microstrip and chipless RFID technologies; however, the identification is carried out through the contact of the object with the reader. In order to make this possible, the spiral resonators in the reader are placed next to a transmission line, each resonator represents a data bit, they resonate freely until a banknote or a document is placed and aligned properly. Each banknote or document must have a metallic mark printed on its inner layer, because it makes falsification difficult and the electromagnetic waves can cross the paper, in such a way that each metallic mark establishes a binary code. The metallic marks suppress the resonances of the resonators located in the reader. In other words, the marks can change the bits state, 0 or 1, corresponding to the presence and absence of resonance, respectively. The system also has the potential to increase the volume of data encoding with the possibility of the ternary system, when the resonances have three states. Simulation and measurement results are also presented in this workMestradoTelecomunicações e TelemáticaMestre em Engenharia ElétricaCAPE

Conception de tags d'identification sans puce dans le domaineTHz

This thesis work deals with the development of a new generation of low-cost Chipless tags operating in the THz frequency domain, it has been supported by the french national agency for research (ANR-09-VERS-013 « THID » ). It covers a wide area of applications such as the identification and/or unitary authentication of commercial items, identity papers, access control…To manufacture these tags, we proposed to use a periodic stack of dielectric material layers with different refractive index and whose thickness is of the order of the wavelength, commonly known as a one dimensional photonic crystal. The electromagnetic signature of such a structure exhibits photonic bandgaps (PBG), i.e. frequency windows in which light propagation is prohibited. We suggested modifying the periodicity of the crystal to create defect levels (peaks) for example in the 1st PBG to encode binary information. This particular structure allows to precisely tuned an electromagnetic signature. To ensure a mass and cost effective industrialization, we retained basic materials which are widely used in the pulp and paper industry: paper and polyethylene. The choice of these materials, which must combine high index contrast and low absorption, represents the first and a crucial step in this work. We characterize a wide range of materials using classical THz time domain spectroscopy (THz-TDS) and we propose two families of tags based on paper and polyethylene. Furthermore, we developed two methods to encode binary information, both based on the absence or presence of peaks in a PBG, peaks whose number and position depend on the introduced defects of periodicity. In a real identification test, a coding capacity of nearly 20-bit has been demonstrated. We also showed that the information contained in the electromagnetic response of these THz tags can be used for other applications related to the unitary authentication and by using the correlation coefficient as criterion for discrimination of the different signatures. Therefore, we evaluate the performance of an authentication test based on this criterion in various analysis domains: time, frequency and time-frequency. We showed that a study of the spectrogram (combining time and frequency representation) is much more relevant than a study in the only time or frequency domain.Ce travail de thèse a été réalisé dans le cadre d'un contrat avec l'ANR (ANR-09-VERS-013 « THID ») et porte sur le développement d'une nouvelle génération de tags Chipless à bas coûts fonctionnant dans le domaine THz, pour des applications d'identification et/ou authentification unitaire des articles commerciaux, des papiers d'identités, des personnes pour le contrôle d'accès... Les structures proposées, constituées d'un empilement périodique de couches diélectriques d'indices de réfraction différents, utilisent les propriétés particulières des cristaux photoniques 1D de présenter une réponse électromagnétique entrecoupée de bandes interdites photoniques (BIP). Toute perturbation de la périodicité de la structure engendre des pics dans les bandes interdites qui sont utilisés pour coder une information binaire. Cette structuration particulière des matériaux permet donc de manipuler précisément une signature électromagnétique. Pour des raisons liées à l'industrialisation (facilité de fabrication en masse) et aussi de coût, nous avons retenu des matériaux de base déjà couramment utilisés dans l'industrie papetière : le papier et le polyéthylène. Le choix de ces matériaux, qui doivent allier contraste d'indice élevé et faible absorption, représente une étape cruciale dans ce travail. Ainsi, à partir des résultats expérimentaux obtenus par spectroscopie THz dans le domaine temporel (THz-TDS) sur un grand nombre de matériaux, nous avons pu concevoir deux familles de tags sur la base de ces différents matériaux. Par ailleurs, nous avons développé deux méthodes de codage d'une information binaire, toutes deux basées sur l'absence ou la présence de pics dans une BIP, pics dont la position et le nombre dépendent bien évidemment des défauts de périodicité introduits. Pour des applications liées à l'identification, des capacités de codage de près de 20 bits ont été démontrées. Nous avons aussi montré que la richesse d'information contenue dans la réponse électromagnétique de ces Tags THz peut être utilisée pour les applications liées à l'authentification unitaire, en utilisant comme critère de discrimination le coefficient d'autocorrélation. Nous avons ainsi pu évaluer les performances d'un test d'authentification basé sur ce critère dans différents domaines d'analyse : temporel, fréquentiel et temps-fréquence. Nous avons montré qu'une étude du spectrogramme (combinant temps et fréquence) est ainsi bien plus pertinente qu'une étude dans les seuls domaines temporel ou fréquentiel

Near-field chipless-RFID system with high data capacity for security and authentication applications

A high data capacity chipless radio frequency identification (chipless-RFID) system, useful for security and authentication applications, is presented in this paper. Reading is based on the near-field coupling between the tag, a chain of identical split-ring resonators (SRRs) printed on a (typically flexible) dielectric substrate (e.g., liquid crystal polymer, plastic, and paper), and the reader. Encoding is achieved by the presence or absence of SRRs at predefined (equidistant) positions in the chain, and tag identification (ID) is based on sequential bit reading. Namely, the tag must be longitudinally displaced, at short distance, over the reader, a microstrip line loaded with an SRR and fed by a harmonic signal. By this means, the harmonic signal is amplitude modulated, and the (ID) code is contained in the envelope function, which can be obtained by means of an envelope detector. With this system, tag reading requires proximity with the reader, but this is not an issue in many applications within the domain of security and authentication (e.g., secure paper for corporate documents and certificates). Several circularly shaped 40-bit encoders (implemented in a commercial microwave substrate), and the corresponding reader, are designed and fabricated as proof-of-concept demonstrators. Strategies for programming the tags and a first proof-of-concept chipless-RFID tag fabricated on plastic substrate through inkjet printing are included in this paper

Double-stub loaded microstrip line reader for very high data density microwave encoders

Compact and high-data density microwave encoders useful for motion control and near-field chipless radio frequency identification (chipless-RFID) applications are proposed in this paper. The encoders are chains of metallic strips etched on a dielectric substrate. The reader consists of a microstrip line loaded with a pair of identical open-ended folded stubs located at different positions and oriented face-to-face by their extremes. By displacing the encoder over the extremes of the stubs, interstub coupling arises when a strip is located on top of the stubs, thereby generating two transmission zeros (rather than one) in the frequency response of the line. Thus, the presence of a strip on top of the face-to-face stubs produces a variation in the transmission coefficient of the line, which in turn can be detected by feeding the line with a harmonic signal, conveniently tuned. Encoder motion generates an amplitude modulated (AM) signal at the output port of the line with peaks, or dips, separated by a time distance dictated by the relative velocity between the reader and the encoder. Moreover, by making certain strips of the chain inoperative (e.g., by cutting them), it is possible to encode information that can be read as the absence (logic state "1") or presence (logic state "0") of peaks, or dips, at predefined positions in the output AM signal of the reader line. Since short strips suffice to generate interstub coupling, unprecedented data density per surface (DPS = 26.04 bit/cm 2 ) is obtained, as revealed by the implementation of 6.4 mm × 60 mm 100-bit encoder

Multistate multiresonator spectral signature barcodes implemented by means of S-shaped split ring resonators (S-SRR)

Spectral signature barcodes functional at the S frequency band are presented in this paper. The barcodes are implemented by loading a coplanar waveguide transmission line by means of multiple S-shaped split ring resonators (S-SRRs), each one tuned to a different frequency. The main particularity of this paper is the fact that more than two logic states (i.e., three or four, depending on the implementation) are assigned to each resonant element. By this means, the total number of bits of the barcode (for a given number of resonators) is increased, as compared with previous approaches based on two logic states per resonator. This multistate functionality is achieved by rotating the S-SRRs. Such rotation modulates the line-to-resonator coupling intensity, and consequently the notch depth at the S-SRR fundamental resonance. Therefore, by considering three or four fixed rotation angles (or orientations) between the line axis and the S-SRR (for the triand fourstate multiresonator barcodes, respectively), intermediate levels between the maximum and minimum attenuation are achieved. This multistate strategy only exploits a single frequency per resonant element (the fundamental one). Therefore, the data capacity per bandwidth are improved as compared with twostate-based barcodes or to multistate barcodes that use two frequencies per resonant element. As illustrative examples, two different four-state multiresonator barcodes with eight S-SRRs (providing 48 = 65.536 different codes, or 16 bits) and with nine S-SRRs (equivalent to 18 bits), occupying a spectral bandwidth of 1 GHz and less than 6.75 and 8.2 cm2, respectively, are designed, fabricated, and characterized

A Novel RFID EMSICC-based Chipless Tag

A new Radio Frequency Identification (RFID) chipless tag based on the Substrate Integrated Waveguide (SIW) technology is proposed in this paper. The tag highlights the importance of using such technologies allowing a surface miniaturization, a high Q-factor and an original shape. Thus, the novel design consists of an Eight-Mode Substrate Integrated Circular Cavity (EMSICC) associated to an Ultra Wideband (UWB) bowtie-shaped antenna. The EMSICC is realized by bisecting the Quarter Mode Substrate Integrated Circular Cavity (QMSICC) into two parts, while preserving the same resonant frequency and the original electric field distribution. Further, the operating frequency band is from 5 GHz to 8 GHz within a compact area of 4.97 × 1.05 cm2. The proposed design is experimentally validated in the frequency domain

High-density microwave encoders for motion control and near-field chipless-RFID

A novel microwave system for measuring linear displacements and velocities with sub-millimeter resolution and for the implementation of near-field chipless radiofrequency identification (chipless-RFID) systems with very high data capacity is presented. The system is based on a reader, consisting of a half-wavelength straight resonator coupled (through capacitor gaps) to a pair of access lines, and a microwave encoder, in relative motion to the reader and consisting of a linear chain of strips orthogonally oriented to the chain axis. By displacing the encoder over the half-wavelength resonator of the reader, with the encoder strips parallel oriented to the reader axis, the relative velocity and position between the encoder and the reader can be inferred. For that purpose, the reader is fed by a harmonic signal tuned to the resonance frequency that results when an encoder strip is perfectly aligned with the reader. The encoder motion amplitude modulates the feeding signal at the output port, and both the position and the velocity are measured from the peaks, or dips, of the resulting envelope function. Moreover, by making certain strips inoperative, the system can be used for coding purposes. Due to the small period of the encoder (0.6 mm), a high per-unit-length data density in these near-field chipless-RFID tags (i.e., 16.66 bits/cm) is achieved. To illustrate the functionality and potential of the approach, 100-bit chipless-RFID tags with various ID codes are implemented and rea

Electromagnetic Absorbers Based on Frequency Selective Surfaces

Frequency Selective Surfaces (FSSs) are bidimensional arrays of particles arranged in a periodic manner. These surfaces can be lossless or lossy, depending on the manufacturing process. They can be fabricated by using metallic or controlled-resistance surface deposition. Lossy surfaces can be also obtained through the integration of lumped components on a metallic surface. The use of FSSs has fostered new research lines in the design of electromagnetic absorbing surfaces, bringing improvements both in terms of bandwidth/thickness ratio maximization and in terms of customizability of the absorbing bandwidth (narrowband, multi-band, wideband, ultra-wideband) for specific applications. Artificial impedance surfaces (or HighImpedance Surfaces, - HIS) are thin resonant cavities synthesized by printing a periodic frequency selective surface on the top of a grounded dielectric slab. By proper tailoring of the geometrical and electrical properties of the FSS as well as the substrate, several electrically-thin absorbing designs can be obtained. Ultranarrowband absorbers with extremely stable angular behavior, often addressed as metamaterial absorbers, can be realized by exploiting only dielectric losses of commercial substrates. Narrowband, wideband and ultra-wideband configurations are instead implemented by also resorting to ohmic losses in a non-conductive FSS. A thorough review of the available absorbers will be presented together with multi-band and tunable design techniques. Manufacturing processes and practical examples will be also addressed, and the most interesting fields of application of the presented structures will be described

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium