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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Chipless RFID Authentication examines the development of highly secure product authentication systems for manufactured products by using chipless radio frequency identification (RFID) technology. The absence of a chip and its compatibility with mass production make chipless RFID an alternative to barcodes. This book discusses how, by using natural randomness inherent to the fabrication process, each chipless RFID tag has a unique signature that can never be reproduced, even if someone tries to copy the label. The book first explores the state-of-the-art of existing authentication and anti-counterfeiting methods based on their security level. Next, a methodology describing the characterization of chipless RFID tags for the authentication application is presented, followed by a discussion of the extraction of aspect-independent parameters for chipless RFID tags. After proposing designs for the tags, the book presents the realization and characterization of the labels (which exhibit naturally occurring randomness) for authentication, using printed circuit boards and inkjet printing on polyethylene terephthalate.
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Table of Contents
Cover
Title Page
Copyright Page
Preface
1 Introduction to Chipless Radio Frequency Identification
1.1. Introduction
1.2. Chipless radio frequency identification
1.3. Recent developments and advancements
1.4. Authentication
1.5. Conclusion
2 Literature Review
2.1. Introduction
2.2. State of the art
2.3. Conclusion
3 Methodology and Proof of Concept
3.1. Introduction
3.2. Randomness inherent in the realization process
3.3. Authentication procedure
3.4. Statistical analysis
3.5. Chipless tag discrimination using PCB tags
3.6. Chipless tag discrimination using inkjet-printed paper tags
3.7. Conclusion
4 Extraction of Chipless Tag Key Parameters from Backscattered Signals
4.1. Introduction
4.2. Chipless RFID tags and measurement setup
4.3. Extraction of aspect-independent parameters of a second-order scatterer
4.4. Extraction of CNRs of the multi-scatterer-based tags
4.5. Comparison of computational time durations between the matrix pencil method and the spectrogram method
4.6. Conclusion
5 Chipless Authentication Using PCB Tags
5.1. Introduction
5.2. Design and the optimization of chipless tags to be employed for authentication
5.3. Detection of minimum dimensional variation in outdoor realistic environment and authentication results
5.4. Detection of natural randomness and authentication results
5.5. Conclusion
6 Chipless Authentication Using Inkjet-Printed PET Tags
6.1. Introduction
6.2. Optimization of chipless tags to exploit natural randomness inherent in inkjet printing
6.3. Authentication using VNA-based chipless reader
6.4. Authentication using IR-UWB chipless reader
6.5. Conclusion
Conclusion
Appendix A: Calculation of the Effective Permittivity of a Coplanar Stripline
Appendix B: Measurement Setup Inside an Anechoic Chamber
Appendix C: Matrix Pencil Method
References
Index
Other titles from iSTE in Electronics Engineering
End User License Agreement
List of Tables
Chapter 3
Table 3.1.
Dimensional parameters of the three fabricated tags
Table 3.2.
Comparison of measured and theoretical applied dimensional vari
...
Chapter 4
Table 4.1.
Extracted a priori parameters associated with each scatterer of
...
Table 4.2.
Absolute differences of extracted parameters using the spectrog
...
Table 4.3.
Absolute difference of extracted parameters using the spectrogr
...
Table 4.4.
Absolute differences of extracted parameters using the spectrog
...
Chapter 5
Table 5.1.
Four extreme cases of dimensional variations of average Lm and
...
Chapter 6
Table 6.1.
Sensitivity (change in the frequency of resonance ∆fr) for each
...
Table 6.2.
Evolution of the probability of error in comparison to the vert
...
List of Illustrations
Chapter 1
Figure 1.1.
Numerous coding techniques for the chipless RFID technology. F
...
Figure 1.2.
Radar principle of operation of an REP-based chipless RFID sys
...
Figure 1.3.
Examples of REP-based chipless RFID tags. (a) C-folded scatter
...
Figure 1.4.
The developments and advancements in the REP-based chipless RF
...
Figure 1.5.
SEM photograph of a normal paper. For a color version of this
...
Figure 1.6.
Overview of the chipless authentication concept
Chapter 2
Figure 2.1.
Types of security technologies. For a color version of this fi
...
Figure 2.2.
Existing product anti-counterfeiting or authentication techniq
...
Figure 2.3.
Some examples of visible features (security level 1) generated
...
Figure 2.4.
Some examples of covert features (security level 2) generated
...
Chapter 3
Figure 3.1.
A layout to explain a change in the width of the inkjet-printe
...
Figure 3.2.
Principle of the authentication procedure. (a) Pre-stage: form
...
Figure 3.3.
The concept of statistical analysis of the proposed approach.
...
Figure 3.4.
Top view of fabricated PCB C-folded tags. For a color version
...
Figure 3.5.
Measurement of applied dimensional variations along parameters
...
Figure 3.6.
Measurement setup in an anechoic environment. For a color vers
...
Figure 3.7.
Time windowing procedure for the reflection coefficient S11 of
...
Figure 3.8.
(a) Intra- and inter-tag cosine similarity distributions for F
...
Figure 3.9.
Top view of paper inkjet-printed tags based on classical C-fol
...
Figure 3.10.
Time windowing procedure for the reflection coefficient S11 o
...
Figure 3.11.
Description of signals’ comparison conventions for comparison
...
Figure 3.12.
Similarity analysis for the inkjet-printed paper tags. (a) In
...
Figure 3.13.
Microscope image of the upper arm of C-folded scatterer of th
...
Chapter 4
Figure 4.1.
Measurement setup used in an anechoic environment and in a rea
...
Figure 4.2.
Measured
|
S
21
|
for the single dual-L dipole in an anechoic env
...
Figure 4.3.
Flowchart of the extraction of CNRs using the matrix pencil me
...
Figure 4.4.
Time windowing procedure for the single dual-L tag’s uncalibra
...
Figure 4.5.
Extraction of poles of the single dual-L dipole tag using the MP
...
Figure 4.6.
Flowchart of the spectrogram method
Figure 4.7.
Extraction of CNR by the spectrogram method for the single dua
...
Figure 4.8.
Calculation of parameters of STFT averaging window from the de
...
Figure 4.9.
Comparison of the MPM and the spectrogram method. (a) Reconstr
...
Figure 4.10.
Extraction of CNRs by spectrogram method for the six dual-L d
...
Figure 4.11.
Comparison of the MPM and the spectrogram method. (a) Reconst
...
Figure 4.12.
Extraction of CNRs by the spectrogram method for the six dual
...
Figure 4.13.
Comparison of the MPM and the spectrogram method. (a) Reconst
...
Figure 4.14.
Extraction of CNRs by spectrogram method with dedicated avera
...
Figure 4.15.
Comparison of extracted complex poles for the six dual-L dipo
...
Figure 4.16.
Windowed TD responses with window length TLW ranging from 100
...
Figure 4.17.
Comparison of computational time durations between the spectr
...
Chapter 5
Figure 5.1.
Layout of the simulated C-folded uni-scatterer tag. Inset: the
...
Figure 5.2.
(a) Simulated CST backscattered TD responses. (b) Simulated CS
...
Figure 5.3.
Similarity level calculated in both FD [3.1] and TD [3.2] usin
...
Figure 5.4.
Top view of the fabricated C-folded uni-scatterer tags along w
...
Figure 5.5.
Measurement setup for C-folded uni-scatterer tags in an anecho
...
Figure 5.6.
Time windowing of the transmission coefficient S21 of the C-fo
...
Figure 5.7.
Cosine similarity map obtained by comparing a reference comple
...
Figure 5.8.
Layout of the simulated C-folded quad-scatterer tags. Inset: t
...
Figure 5.9.
(a) The simulated CST backscattered TD responses. (b) The simu
...
Figure 5.10.
Similarity levels calculated in both FD [3.1] and TD [3.2] us
...
Figure 5.11.
Top view of the fabricated C-folded quad-scatterer tags along
...
Figure 5.12.
Measurement setup for the C-folded quad-scatterer tags in a c
...
Figure 5.13.
Time windowing of the transmission coefficient S21 of the C-f
...
Figure 5.14.
Cosine similarity map obtained by comparing a reference compl
...
Figure 5.15.
Top view of the fabricated C-folded quad-scatterer tags along
...
Figure 5.16.
Time windowing of the transmission coefficient S21 of the C-f
...
Figure 5.17.
Cosine similarity map obtained by comparing a reference compl
...
Figure 5.18.
Measurement setup of a digital microscope. Also, the USAF 195
...
Figure 5.19.
A sample image of the measurement of dimensions. Also, an edg
...
Figure 5.20.
Measured arms’ length L'm for all groups in comparison to the
...
Figure 5.21.
(a) Intra-group and inter-group cosine similarity distributio
...
Figure 5.22.
Top view of the first realization of C-folded quad-scatterer
...
Figure 5.23.
Similarity analyses for the first realization. (a) Intra- and
...
Figure 5.24.
Similarity analyses for the second realization. (a) Intra- an
...
Figure 5.25.
Similarity analyses for the first realization versus second r
...
Figure 5.26.
Measurement dimensional parameters from microscope digital im
...
Figure 5.27.
Microscopic dimensional characterization for both intermitten
...
Figure 5.28.
Range of the similarity change happened due to the natural ra
...
Figure 5.29.
Exponential decay of the probability of error with the increa
...
Chapter 6
Figure 6.1.
An analogy of the vertex-to-vertex adjacent metallic geometrie
...
Figure 6.2.
Layouts of the C-folded scatterers. (a) Conventional design of
...
Figure 6.3.
Simulated backscattered responses of the layouts shown in Figu
...
Figure 6.4.
Illustrations of variations in the lengths of the beginning in
...
Figure 6.5.
Randomness in inkjet printing using the Epson C88+ printer wit
...
Figure 6.6.
The input digital mask of check patterns 2with a vertex-to-ver
...
Figure 6.7.
Top view of inkjet-printed tags based on the check-patterned C
...
Figure 6.8.
Measurement setup in an anechoic environment with the VNA-base
...
Figure 6.9.
Time windowing to discard the structural mode and to extract t
...
Figure 6.10.
First measurement of S11 in the form of windowed FD responses
...
Figure 6.11.
Five repetitive measurements of S11 in the form of windowed F
...
Figure 6.12.
Similarity analysis for the inkjet-printed PET three-square c
...
Figure 6.13.
Similarity analysis for the inkjet-printed PET five-square ch
...
Figure 6.14.
Measurement setup in an anechoic environment with the IR-UWB
...
Figure 6.15.
Time windowing to discard the structural mode and to extract
...
Figure 6.16.
The first measurement of S21 in the form of windowed FD respo
...
Figure 6.17.
Five repetitive measurements of S21 in the form of windowed F
...
Figure 6.18.
Similarity analysis for the inkjet-printed PET five-square ch
...
Appendix 1
Figure A.1.
Coplanar stripline C-folded scatterer with finite substrate thic
...
Appendix 2
Figure B.1.
Measurement setup inside an anechoic chamber. For a color versio
...
Guide
Cover Page
Title Page
Copyright Page
Preface
Table of Contents
Begin Reading
Appendix A Calculation of the Effective Permittivity of a Coplanar Stripline
Appendix B Measurement Setup Inside an Anechoic Chamber
Appendix C Matrix Pencil Method
References
Index
Other titles from iSTE in Electronics Engineering
WILEY END USER LICENSE AGREEMENT
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Series Editor
Etienne Perret
Chipless RFID Authentication
Design, Realization and Characterization
Zeshan Ali
Etienne Perret
Nicolas Barbot
Romain Siragusa
First published 2022 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.
Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:
ISTE Ltd
John Wiley & Sons, Inc.
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www.iste.co.uk
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© ISTE Ltd 2022The rights of Zeshan Ali, Etienne Perret, Nicolas Barbot and Romain Siragusa to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s), contributor(s) or editor(s) and do not necessarily reflect the views of ISTE Group.
Library of Congress Control Number: 2022936226
British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-78630-833-7
Preface
Counterfeiting has become a global and dynamic phenomenon, as in 2013 the total international trade of counterfeited items was up to 2.5% of the global trade. This illicit practice poses threat to a wide range of industries and harms societies from various perspectives: ultraexpensive consumer goods (e.g. cosmetics, fragrances, leather articles, jewelry), business-to-business goods (e.g. tools, appliances, materials, replacement parts) and essential consumer goods (e.g. food items, medicines). Product authentication offers vast opportunities to combat fakes in the global supply chain. Therefore, robust and reliable authentication methods have become a global demand to limit counterfeiting.
This book is focused on taking the next step with the aim of developing chipless tags for highly secure product authentication applications. The concept of conventional chipless radio frequency identification (RFID) is extended to the authentication where each tag has to present a unique signature that can never be reproduced even if someone tries to copy the tag. For this purpose, natural randomness (i.e. inherent in the fabrication process) along the dimensional parameters of resonators is used. Such natural randomness can produce unique electromagnetic (EM) signatures that can be used for authentication. First, a methodology to characterize the chipless RFID tag for authentication applications is presented. This methodology consists of procedures to conduct both authentication and statistical analyses. The capabilities of chipless technology to be used for tag discrimination are demonstrated by purposely applying the dimensional variations using two technologies: printed circuit board (PCB) and inkjet printing. Then, the extraction of aspect-independent parameters for chipless RFID tags is presented. For authentication purposes, aspect-independent parameters are directly associated with the physical dimensions of the scatterer of a chipless tag, but not associated with the measurement procedure. The random variation of the physical dimensions of the scatterers is then associated with aspect-independent parameters, which is particularly promising for chipless authentication. On the other hand, with the operation of a single measurement, the proposed extraction of aspect-independent parameters is very promising for the practical implementation of the chipless RFID technology. Finally, chipless authentication methods using naturally occurring randomness in the realization process of PCB chipless tags and inkjet-printed polyethylene terephthalate (PET) chipless tags are presented. The optimization of chipless RFID tags for each realization technology (PCB and inkjet printing) is presented. This optimization is performed to exploit the natural process variations effectively for the purpose of authentication, unlike the conventional chipless RFID tags that are not capable of exploiting the variations effectively. To prove this concept, sufficiently large populations of chipless RFID tags are taken. For PCB, chipless RFID tags are realized two times intermittently, where each realization consists of 45 tags. The two different realizations share the same company, the same PCB technology, but a different film mask, in order to ensure the natural dimensional randomness. Similarity analyses are conducted within each realization, as well as between two intermittent realizations. Finally, the technique is generalized to decrease the probability of error to a significant level. For inkjet-printed PET tags, an evolution of the probability of error is presented in comparison to the optimization of the design of chipless tags. The performance of the system is analyzed by a highly accurate vector network analyzer (VNA)-based reader and a low-cost impulse radio (IR) ultra-wideband (UWB) chipless reader. The probability of error achieved is comparable to the various fingerprint evaluation campaigns found in the literature.
Chapter 1 introduces the chipless RFID technology and its sub-branches. It also discusses the recent developments and advancements in the field of chipless RFID technology. Finally, it presents the challenges of the development of robust authentication techniques.
Chapter 2 presents a brief literature review of numerous existing authentication techniques based on their security level. Apart from existing authentication techniques, this chapter also discusses the necessity of a database for a highly secure authentication application.
Chapter 3 presents a methodology to characterize chipless RFID tags for authentication applications, where procedures to conduct authentication and statistical analyses are presented. The capabilities of chipless technology to be used for tag discrimination are demonstrated using two technologies: PCB and inkjet printing. To validate this approach, three chipless RFID tags are realized. Consecutively from one tag to another, a variation (in the order of fabrication tolerance) is purposely applied to the geometrical dimensions exhibiting the lowest impact on the signal. Chipless tag discrimination based on the level of similarity is presented in both the frequency and time domains.
Chapter 4 presents the extraction of aspect-independent parameters for chipless RFID tags. The extraction of these parameters is needed for authentication because: (i) fewer resources would be needed to save the aspect-independent parameters in the database of authenticity, and (ii) if the chipless tags to be used for authentication are based on multi-scatterers, then the aspect-independent parameters cannot be extracted using only the fast Fourier transform (FFT) approach. Robust detection of depolarizing REP tags using FFT-based short-time Fourier transform is demonstrated. It is demonstrated that, in the frequency-coded chipless RFID technology, as the resonances of the scatterers are orthogonal to each other, the spectrogram method is an efficient and fast choice. The extraction of complex natural frequency(ies) using the spectrogram has never before been performed in the field of frequency-coded chipless RFID. For authentication purposes, aspect-independent parameters are directly associated with the physical dimensions of the scatterer of a chipless tag, but not with the measurement procedure. The random variation of the physical dimensions of the scatterers is then associated with aspect-independent parameters, which is particularly promising for chipless authentication. On the other hand, with an operation of a single measurement, the proposed technique is very promising for the practical implementation of the chipless RFID technology, as it is computationally less expensive due to the inherent fast property of FFT. Thus, the proposed technique requires fewer resources and efforts.
Chapter 5 presents chipless authentication using PCB chipless tags. For this purpose, first, it is shown that the four-coupled C-folded scatterer-based chipless tag is a better choice than the single C-folded scatterer-based chipless tag. Then, the randomness along the geometrical dimensions of a C-folded resonator is analyzed by a second-order bandpass filter model. The concept is proved by fabricating three groups of tags (quad C-folded scatterer tags), which show distinct arms’ length, to account for randomness due to the fabrication process. Subsequently, natural dimensional variations in the design of C-folded tags are analyzed for authentication applications. For this purpose, four coupled C-folded scatterer based chipless tags are chosen because of their sharp slope dissimilarity. The chipless tags are realized two times intermittently, where each realization consists of 45 tags. The two different realizations share the same company, the same PCB technology, but a different film mask, in order to ensure the natural dimensional randomness. Similarity analyses are conducted within each realization and between two intermittent realizations. Finally, the technique is generalized to reduce the probability of error to a significant level.
Chapter 6 presents chipless authentication using PET chipless tags printed with a low-cost off-the-shelf available office inkjet printer. The proposed method is based on cheap inkjet-printed square check-patterned tags, whose design is specially optimized by taking the inkjet printing randomness into account. An evolution of the probability of error is also presented in comparison to the vertex-to-vertex gap among the squares of the check pattern. The probability of error achieved is comparable to the various fingerprint evaluation campaigns found in the literature. The performance of the system is analyzed by a highly accurate VNA-based reader and a low-cost IR-UWB reader.
Zeshan ALI
Etienne PERRET
Nicolas BARBOT
Romain SIRAGUSA
June 2020
1Introduction to Chipless Radio Frequency Identification
1.1. Introduction
In this chapter, we provide an introduction to the chipless RFID technology. After a brief discussion, the recent developments and advancements in the field of chipless RFID technology are presented. In this book, we focus on the development of chipless RFID authentication. For this reason, we also discuss some challenges of the development of robust authentication techniques. This chapter is organized as follows:
– section 1.2 presents the introduction of the chipless RFID technology;
– section 1.3 summarizes the recent developments and advancements from the literature in the field of chipless RFID technology;
– section 1.4 presents numerous challenges of the development of robust authentication techniques;
– section 1.5 concludes this chapter.
1.2. Chipless radio frequency identification
Chipless RFID tags, also called RF barcodes, have several advantages over the conventional passive RFID technology. The absence of any chip (which is the reason it is called chipless) connected to the antenna is the primary revolution of this technology. Chipless RFID is very promising, as it is fully printable, low cost, simple in design and non-line-of-sight operation technology. This technology has enormous potential to replace the barcode in item-level tagging (Perret 2014, Chap. 1).
Coding techniques for the chipless RFID technology can be classified into two main categories: time-coded and frequency-coded chipless tags, as shown in Figure 1.1.
Figure 1.1.Numerous coding techniques for the chipless RFID technology. For a color version of this figure, see www.iste.co.uk/ali/RFID.zip
The time-coded chipless technique is first based on sending a pulse signal from the reader to the chipless tag, and then on listening to the backscattered echoes of the transmitted pulse from the tag. The tag code is encoded in the reflected pulse train. On the other hand, in the frequency-coded chipless technique, the tag code is usually encoded by the presence or absence of the peak apexes of resonators. This encoding can also be performed using the phase information at a specified frequency position in the spectrum of the tag. Time-coded chipless tags can be further divided into five categories (Forouzandeh and Karmakar 2015): surface acoustic wave, on–off keying modulation, pulse position modulation, metamaterial structures and multi-frequency pulse position modulation. Frequency-coded chipless tags can be further divided into two categories (Vena et al. 2016b, Chap. 4): tags based on dedicated transmission and reception antennas having a filtering circuit between them, and tags based on an RF-encoding particle (REP). An REP is like a scatterer that behaves like a transmitting antenna, a receiving antenna and a filtering circuit simultaneously. The latter technique outperforms the former one in terms of simplicity of design, low cost, low weight and high coding capacity/area. In the former technique, the presence of dedicated transmission and reception antennas causes the mismatching problem, and, ultimately, these antennas do not play their role in increasing the read range. The only advantage of the former technique is that the design of chipless RFID tags shows a separated form.
The radar principle of operation of an REP-based chipless RFID system is schematized in Figure 1.2. A chipless RFID tag is first illuminated by the reader antenna by placing the tag in the field of the reader antenna. The illuminating signal is then coupled with the tag’s scatterer. Then, the chipless RFID tag backscatters its response. This backscattered signal is read and stored using the acquisition system.
Figure 1.2.Radar principle of operation of an REP-based chipless RFID system
Some examples of REP-based chipless RFID tags (Perret 2014, Chap. 5) are shown in Figure 1.3, where REPs are, for example, C-folded scatterer, nested ring resonator, dual-L dipole and shorted 45° dipole. The nested ring resonators and the nested C-folded scatterers provide promising coding density per surface unit, while the nested ring resonators are also invariant to polarization. The dual-L dipole and the shorted 45° dipole provide a depolarizing operation in the illuminated and backscattered waves. On the other hand, a square-shaped scatterer (Betancourt et al. 2015) and an octagonal scatterer (Betancourt et al. 2016) are also invariant to polarization. Other examples of scatterers are open conical resonators (Nair et al. 2014a, 2014b) and quick response (QR) codes such as resonators (Betancourt et al. 2017).
In the context of this book, we used REP (e.g. C-folded scatterer, dual-L scatterer, shorted 45° dipole) based chipless tags.
Figure 1.3.Examples of REP-based chipless RFID tags. (a) C-folded scatterer-based tag. (b) Nested ring resonator-based tag. (c) Dual-L dipole-based tag. (d) Shorted 45° dipole-based tag. For a color version of this figure, see www.iste.co.uk/ali/RFID.zip
1.3. Recent developments and advancements
Figure 1.4 outlines the recent developments and advancements in the REP-based chipless RFID. Numerous works to enhance the capability of chipless RFID have been reported that are on the aspects of, for example, the tag, the chipless reader, the robustness of detection, sensing and authentication. For the rest of this book, REP-based chipless RFID is simply referred to as chipless RFID.
Figure 1.4.The developments and advancements in the REP-based chipless RFID. For a color version of this figure, see www.iste.co.uk/ali/RFID.zip
The cost of the chipless RFID has been brought to a few € cents, e.g. €0.4 cents as found in Perret (2014, Chap. 1) and Perret et al. (2013), by using the industrial or laboratory equipment. The techniques used are based on:
– printing the paper-based chipless RFID tags using a flexographic technique (Vena et al. 2013b);
– printing the PET-based chipless RFID tags using screen printing for fast mass production of tags (Nair et al. 2014a, 2014b; Betancourt et al. 2015, 2017). Furthermore, a cost reduction of at least 96% or at least 69% is expected by respectively replacing silver with copper or copper with aluminum with respect to market prices (Barahona et al. 2016a).
For improving the coding capacity of chipless RFID tags, the scientific community has intensified its research efforts. Many examples can be found in Khan et al. (2016, Table III). Predominantly, encoding in chipless RFID tags is based on the shift of the peak apexes associated with resonant scatterers. This type of encoding is called frequency position encoding. To further enhance the coding capacity, the tag is coded using phase deviations along with the frequency position, as shown in Vena et al. (2011, 2016b, Chap. 4). This type of coding may double the coding capacity even with simple REPs (see Figure 1.3). Further advancement of coding capacity has been discussed in Rance et al. (2017, Chap. 4), which introduces magnitude coding based on the radar cross section (RCS).
Reconfigurable chipless RFID tags can be divided into two categories: write-only capable chipless RFID tags and rewritable chipless RFID tags. The activation of reconfigurability can be carried out in the form of additive conductive strips on the resonators in an invasive manner (i.e. by a mechanical trigger) or by applying a voltage or laser pulse to specially designed switches (i.e. by an electrical trigger). In write-only capable chipless RFID tags, many non-effective resonators are added in the design of chipless tags. Without the reconfigurability trigger, the frequencies of resonance of these non-effective resonators do not fall within the frequency band of operation of the chipless RFID tag. When the reconfigurability trigger is applied, these additive (non-effective) resonators become effective, showing their frequencies of resonance within the frequency band of operation of the chipless RFID tag. Hence, this category is called write-only capable chipless RFID tags. On the other hand, in rewritable chipless RFID tags, resonators (in the design of chipless tags) are always effective. When the reconfigurability trigger is applied to these effective resonators, there are shifts in the position of the frequencies of resonance within the frequency band of operation of the chipless RFID tag. Therefore, this category is called rewritable chipless RFID tags.
The write-only capable dual-rhombic loop resonators have been presented in Vena et al
