Brief Description of Radio Frequency Identification (RFID) Technology

I. INTRODUCTION

RFID technology was born for military purposes during the Second World War and represents an evolution of the now obsolete automatic identification systems such as the bar-code (one and two-dimensional), the magnetic card and the contact smart cards described in [1].

Fig. 1: Schematic Diagram of RFID System

The typical RFID identification system shown in figure 1 can be schematized in two main blocks:

? a mobile unit that is applied to the object to be identified and which is normally called a transponder, tag or target;

? an intelligent unit driven by a personal computer (and therefore an application software) is able to carry out communication operations with the tag.

The communication operations are generally operations to read or write information within the transponder memory and queries are defined for this reason. The operations performed by the mobile unit are generally defined as responses because they are always sent following the receipt of a read or write request. The intelligent unit, precisely because it performs read or write operations, is generally referred to as a reader or initiator. On the transponder and on the Reader there is a coupling element that allows to establish a bond necessary to start the communication according to the techniques described in more detail in [1]. The coupling elements generally adopted are the inductor, the capacitor and the antenna. Based on the type of coupling element chosen, we have the exploitation of a physical principle that allows communication between the two devices which are: inductive, electrical and electromagnetic coupling.

The potential possessed by this technology is essentially constituted by the possibility of having transponders without on-board power supply systems and oscillators for generating the carrier because they are made in such a way as to be able to draw power from the RF field imposed by the reader that is maintained for the duration of the communication. The response of the target to the request of the reader occurs consequently by modulating the field generated and imposed by the reader according to two different techniques which are: Load Modulation and σ-Modulation. The first allows to detect a change in the equivalent impedance of the transponder at the ends of the coupler element of the reader just as happens for electrical transformers and is generally used in inductive or electrical coupling systems. The second technique allows the detection of a change in the operation of the transponder following a change in the scattering aperture of the antenna itself which is reflected in a change in the intensity of the RF carrier component reflected by the target in the direction of the reader.

For this reason, the Tag is generally made of a coupling element and a memory chip with RF interface as shown in Figure 2a. Based on the type of communication adopted and the type of coupling used, a rough classification of RFID systems can be made in:

? Active, Passive or semi-passive;

? Inductive, capacitive or backscattering.

For further information on the classification and the characteristics possessed by the different types of RFID systems, see [1].

Fig. 2. Structure of a Transponder: (a) R / W Memory, (b) dual interface Memory

II. MOST USED PROTOCOLS.

The sector of use of automatic identification systems developed with RFID technology are many and for this reason there is a wide range of standards (both proprietary and non-proprietary) that define:

? the electrical and mechanical parameters of the transponders and readers;

? the radiofrequency interface;

? the communication protocol;

? the operating range of the system, generally also defined as the interrogation range.

Figure 3 shows a graph that describes the diffusion of the different protocols. The analysis shows a significant diffusion of proprietary protocols. Among the most used non-proprietary protocols are ISO 15693 and ISO 14443 developed to manage 13.56 MHz communications of inductively coupled RFID systems. The substantial difference between the two is represented by the fact that the former is adopted generally for the item management sector, while the latter is massively adopted for high-level security applications in the payment and access control sector.

Other sectors where RFID systems are widely used are: animal identification in compliance with the protocol ISO 11784 and ISO 11785, anti-theft systems, identification of containers in compliance with the EPC Global, ISO 18000-5 and ISO 18000-6 protocols, etc.

Fig. 3. Analysis of the diffusion of use of the different protocols on a sample of 96 RFID modules. information on this can be found in [2], [3], [4], [5], and [6].

III. DEVICES ON THE MARKET.

The devices and semi-finished transponders marketed by large electronic industries for the realization of RFID targets are divided into:

? Read-Only Memory;

? Read / Write Memory;

? Segmentation Memory;

? Dual Interface Memory;

? Microprocessor Card;

? Dual Interface Microprocessor Card.

Each family of devices just mentioned has been designed for the creation of transponders to be used for specific applications ranging from reading the Unique Identifier, reading / writing data in memory, managing various information on the same tag while maintaining confidentiality; the creation of transponders capable of supporting not only the current wireless interface, but also the traditional contact one; specific applications for data encryption, recognition of persons and payment. Further information on the type of products on the market can be found in [1].

REFERENCES

[1]       Valerio Giampà, “Progettazione, test e collaudo di un sensor tag RFID per applicazioni nel settore dell’item management.”;

[2]       Standard ISO 14443 – www.iso.org;

[3]       Standard ISO 15693 – www.iso.org;

[4]       Protocol NFCIP-1 o ECMA-340 – www.ecma-internationa.org;

[5]       Standard ISO 7816 – www.iso.org;

[6]               www.nfcforum.com ,