Cover Page

FOCUS SERIES

Non-linearities in Passive RFID Systems

Third Harmonic Concept and Applications

Gianfranco Andía

Yvan Duroc

Smail Tedjini

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Acknowledgments

Le Temps de Lecteurs

Dans une taverne de Valence

Où se retrouvaient tous les chercheurs

Nous discutions de radiofréquence

Des étiquettes, ainsi que des lecteurs….

C’était le temps des fleurs

On ignorait la peur

Le mot “docteur” avait un goût de miel

Ton bras prenait mon bras,

Ta voix suivait ma voix,

On était jeune

Et l’on croyait au ciel…

Et puis sont venus les jours de brume

Avec des bruits étranges et des pleurs

Combien j’ai passé de nuit sans lune

A chercher l’étiquette avec le lecteur…

Et ce soir je suis devant la porte

De la taverne ici même à Valence

Et la chanson que la nuit m’apporte

Il y a beaucoup de radiofréquences!

Tout comme au temps des fleurs

Où l’on vivait sans peur

Où chaque jour avait un goût de miel

Ton bras prenait mon bras,

Ta voix suivait ma voix …

Aujourd’hui nous

Croyons encore au ciel!

Pavel Nikitin, Valence, November 2014

The lyrics of this song are credited to Pavel Nikitin, after modifying the lyrics of “Le temps des fleurs” by Dalida.

Pavel was in Valence, France in November 2014 as jury member in the PhD dissertation of Gianfranco and also as speaker in the workshop “Hot topics in RFID/NFC”. These lyrics represent the great memories the authors of this book have about Pavel’s visit, in both scientific and emotional aspects. They would like to celebrate the sincere and fruitful friendship between Yvan, Smail and Gianfranco, and await the possibility of many further joint projects!

About the song

The original version of “Le temps des fleurs” is a Russian romance song “Dorogoi dlinnoyu” (“Дорогой длинною”, literally “By the long road”), composed by Boris Fomin (1900–1948) with words by the poet Konstantin Podrevsky. Gene Raskin then adapted it into English and named it “Those Were the Days”, after which it was adapted to French and sung by Dalida.

Introduction

Since its early commercial application as an anti-theft system in supermarkets, the radio-frequency identification (RFID) technology has become a ubiquitous technology not only in industrial or agricultural areas but also in our daily lives, for instance our car key or access badge. Being able to identify a person, an animal, an object and even hundreds of objects simultaneously has opened up many other applications such as indoor localization and tracking, and further applications involving integration of sensors with RFID. As with the most popular wireless technologies, such as Wi-Fi, Bluetooth or NFC, passive ultra-high-frequency (UHF) RFID has rapidly grown thanks to the standards but also the promotion by industrial organizations such as RAIN RFID Alliance. Nowadays, passive UHF RFID is reliable and technologically and economically lucrative. Although based on relatively simple concepts compared to other wireless technologies using multiple antennas or complex modulations, RFID offers many degrees of liberty that allow the opening of new perspectives and very promising applications. With the idea of preserving devices as simply as possible and enabling the identification of something or somebody, the latest technological achievements in terms of low-power consumption microelectronics along with the exploitation of signal properties not yet used today allow important enhancements in the performance of the RFID system. These improvements include longer read ranges, accurate inventories with high density of tags, data rate and security, which are used in increasingly harsh environments. In parallel, continuous innovation has launched RFID technology as the Internet enabler dedicated to the last meters of tagged things. We can say that the simple backscattering modulation principle has set the path for an open road; the RFID revolution has begun.

In this context, this book focuses on the exploitation of the harmonic signals that are generated by RFID chips in compliance with the passive UHF RFID standard. Even if the topic is all based on RFID, the concepts introduced may also find applications in other fields as long as harmonic signals are present. Chapter 1 introduces RFID technology and its history. It provides the details about current perspectives and expectations in this field. Chapter 2 summarizes the technical fundamentals of the RFID technology and highlights the non-linear circuits present in passive RFID chips and the source of so far “wasted” signals, i.e. harmonic signals existing but not yet used. Chapter 3 presents recent and innovative experimental methods to characterize RFID tags and chips, which provide information about the production of these harmonic signals during a standard RFID communication. Chapter 4 presents theoretical approaches that model and analyze the observed non-linear behavior source of harmonic generation. The study can be used to minimize the “naturally” harmonic signals transmitted by commercial passive UHF RFID tags. On the contrary, in Chapter 5, applications and associated prototypes demonstrate that these unwanted signals can become either an information source with a harmonic tag or an energy source.