Raj Mittra, Pennsylvania State University
RFID (Radio Frequency Identification) is a relatively new approach to automatic identification of products that is slowly but surely replacing, or complementing, the ubiquitous barcode that is currently used for similar purposes. RFID systems rely upon storing and remotely retrieving using tags and transponders attached to products, animals, or persons for the purpose of identification and subsequent inventory control, toll collection, etc., to name just a few. The read distance of the tag depends upon many factors including the operating frequency of the tag, which can range from MHz to GHz ranges and the frequency is chosen on the basis of the application in mind.
RFID technology is now proliferating almost all sectors of modern society, including manufacturing, pharmaceutical, health-care, airline baggage handling, supply chain management, and item-level identification. RFID systems are composed of three major components, namely, Readers, transponders, and antennas. A majority of the transponders are passive or batteryless, and are powered by the energy transmitter by the Reader antenna, though active transponders are finding limited applications in some high-end applications, where security, reliability, and automatic operation capability are of the utmost importance, and can thus justify the use of more costly tags than the passive ones.
Returning to the passive systems the passive transponders are typically laminated with paper or plastic layers to form Smart Labels or Tags, which can communicate with the RFID Readers. The power supplied to the tag by the Reader Antenna is to support Reader Transponder communication during the interrogation process, which includes writing data to the memory of the transponder, and retrieving previously stored information and a unique transponder ID, both of which play important roles when tracking a particular object.
In addition to being read by an RFID reader, the Smart Labels are also readable by an optical scanner and a human and recent increase in interest in Smart Plastic Cards, which include printed texts, barcodes and an RFID Printer-encoder, has led to increased popularity with the credit card industry. This, in turn, had driven up the demand for Printer-Encoders, which in addition to printing and initial encoding, are also used for automated validation procedures for the Smart-Cards, preventing their re-encoding and data corruption. A key component of the transponder is the tag antenna, whose characteristics affect the performance of the RFID system. The antenna characteristics of interest are: gain, radiation pattern, radiation power efficiency, directivity, beamwidth, etc. In the context of RFID, the beamwidth translates into transponder encoding range, and the directivity determines spatial selectivity. Other constraints are acceptable size of the Smart Labels and their placement.
The design of RFID systems is very challenging indeed because of demanding specifications coupled with restrictions on the available size cost, and platform tolerance of tags that may be mounted on a diverse array of products. To meet these challenges it is necessary to combine the expertise on signal processing, antenna technology and system design. This review talk will identify the challenges and describe some of the proposed solutions to address them.
Raj Mittra is Professor in the Electrical Engineering department of the Pennsylvania State University. He is also the Director of the Electromagnetic Communication Laboratory, which is affiliated with the Communication and Space Sciences Laboratory of the EE Department. Prior to joining Penn State he was a Professor in Electrical and Computer Engineering at the University of Illinois in Urbana Champaign. He is a Life Fellow of the IEEE, a Past-President of AP-S, and he has served as the Editor of the Transactions of the Antennas and Propagation Society. He won the Guggenheim Fellowship Award in 1965, the IEEE Centennial Medal in 1984, the IEEE Millennium medal in 2000, the IEEE/AP-S Distinguished Achievement Award in 2002, the AP-S Chen-To Tai Distinguished Educator Award in 2004 and the IEEE Electromagnetics Award in 2006. He has been a Visiting Professor at Oxford University, Oxford, England and at the Technical University of Denmark, Lyngby, Denmark. He has also served as the North American editor of the journal AEÜ.
His professional interests include the areas of Communication Antenna Design, RF circuits, computational electromagnetics, electromagnetic modeling and simulation of electronic packages, EMC analysis, radar scattering, frequency selective surfaces, microwave and millimeter wave integrated circuits, and satellite antennas.
He has published over 950 journal and symposium papers and more than 40 books or book chapters on various topics related to electromagnetics, antennas, microwaves and electronic packaging. He also has three patents on communication antennas to his credit. He has supervised 90 Ph.D. theses, 90 M.S. theses, and has mentored more than 50 postdocs and Visiting scholars. He has directed, as well as lectured in, numerous short courses on Computational Electromagnetics, Electronic Packaging, Wireless antennas and Metamaterials, both nationally and internationally.