RFID Technology
RFID (radio frequency identification) is a form of wireless communication that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum to uniquely identify an object, animal or person. Use cases for RFID technology include healthcare, manufacturing, inventory management, shipping, retail sales and home use.
Principle of RFID Technology
Many types of RFID exist, but at the highest level, we can divide RFID devices into two classes: active and passive. Active tags require a power source—they’re either connected to a powered infrastructure or use energy stored in an integrated battery. In the latter case, a tag’s lifetime is limited by the stored energy, balanced against the number of read operations the device must undergo. One example of an active tag is the transponder attached to an aircraft that identifies its national origin .
Passive RFID is of interest because the tags don’t require batteries or maintenance. The tags also have an indefinite operational life and are small enough to fit into a practical adhesive label. A passive tag consists of three parts: an antenna, a semi- conductor chip attached to the antenna, and some form of encapsulation. The tag reader is responsible for powering and communicating with a tag. The tag antenna captures energy and transfers the tag’s ID (the tag’s chip coordinates this process). The encapsulation maintains the tag’s integrity and protects the antenna and chip from environmental conditions or reagents.
RFID Components
RFID Reader
RFID Antenna
RFID Transponder or Tag
RFID Reader
Function
Depending on the frequency that is used and its performance, an RFID reader sends radio waves of between one centimeter and 30 meters or more. If a transponder enters this electromagnetic region, it detects the activating signal from the reader. The RFID reader decodes the data stored in the integrated circuit of the transponder (silicon chip), and communicates them, depending on the application, to a host system.
Bidirectional Communication
The majority of these devices can both read and write, so data transfer will also work in the reverse direction from the system to the data medium or tag.
The reader is consequently the major component of the system, responsible for activating the transponder and thus for initiating data communication.
Categorization
RFID readers are differentiated by their features, the main ones being stationary or mobile.
Stationary devices are intended for firm incorporation in existing systems, and are the commonest type found. The necessary antenna is attached through an interface. Detected data can be conducted to a host on standard interfaces like RS232, Ethernet or USB.
Mobile readers serve for detecting data on various objects and are notable for their compactness. The antenna is integrated in the device or directly attached to it. Data transfer to a host uses wireless standards like WLAN or DECT.
RFID Antenna
An RFID antenna consists of a coil with one or more windings and a matching network. It radiates the electromagnetic waves generated by the reader, and receives the RF signals from the transponder.
An RFID system can be designed so that the electromagnetic field is constantly generated, or activated by a sensor.
Antennas also come in different sizes and designs, this depending very much on the environment into which a system is integrated. The required read and write range also play a role.
Common forms are rod or loop antennas. For greater reading range or different orientations of a transponder, a number of antennas can be arranged in one reader unit.
LF (Low Frequency) – 125 / 134.2 kHz
HF (High Frequency) – 13.56 MHz
UHF (Ultra High Frequency) – 865 to 950 MHz
In this technology, the antennas are different with regard to configuration and mode of function depending on the frequency used.
The antenna is comprised here of a defined number of wire winds which thereby result in a defined inductance in the antenna. A difference is made here between frame antennas (air coils) and rod antennas (coil with ferrite core). Within the complete system, the magnetic near field is used, i.e. inductive coupling.
Within the HF range, the antenna is comprised of one or more windings and is frequency tuned by a connected tuning board. The antenna winding material should have a large area when possible because in the HF range the waves spread out on the surface of the condustor and more current can flow through a larger area, thereby influencing the performance of the antenna. Within the complete system, the magnetic near field is used, i.e. inductive coupling.
Here a distrinction is made between two types of antenna – dipole and patch antenna. As already suggested by its name, the dipole antenna is a design that comprises two poles. The chip is arranged in the middle and the two antenna poles are to the side. The patch antenna is a metal surface which must have defined edge lengths. The surface thereby functions as a resonator. Within the complete system, the magnetic distant field is used in these antennas, i.e. electromagnetic coupling.
RFID Transponder or Tag
Design of the RFID transponder
The heart of an RFID system is a data carrier, referred to as the transponder, or simply the Tag. The designs and modes of function of the transponders also differ depending on the frequency range, just as with the antennas.
In the LF and HF range, a unique, worldwide ID number is stored on the chip. This can be connected to information in a database. There are coil designs for these two frequencies in the transponders that are used in the magnetic near field of the antennas (inductive coupling).
In the UHF range, the transponder has an EPC (Electronic Product Code) storage area that can be programmed by the customer. Dipoles are used here within the antenna design.
Communication is by means of a backscatter method. Here, data transfer is not by means of inductance, but by changes to the impedance at the transponder antenna, resulting in backscatter. If you now switch this on and off in time with the data flow to be transferred then this results in an amplitude-modulated signal which the scanner or antenna can then receive and process.
Passive transponders are now available with a storage capacity of up to 10kbit, thereby allowing additional information to be stored.
Distinguishing features
The most common distinguishing feature among transponders is their power supply. Both active and passive models are available.
Passive transponders do not have their own power supply and gain their energy from establishing an inductive field from the radio signals of the scanner. The missing source of energy does result in lower ranges, but allows smaller and lighter designs. Additionally, passive transponders are maintenance-free and can be obtained much more cheaply. They are mainly used for product authentication and tracking, but also as data storage media for access control systems.
Active transponders draw their energy from a built-in battery and can therefore transmit signals themselves for data transfer. Due to their integrated power supply, they are more expensive than their passive counterparts but have a wider scanning range of up to 100 meters. They are mainly used to identify objects with a long lifetime and that can be used repeatedly.
Designs
Depending on their purpose, transponders are available in various sizes, designs and protection classes. The most common types are self-adhesive labels or chip cards. They are available as "read only" versions, which can only be read-out, and "read/write" versions that can both read and write the transponder.
RFID Middleware is a radio-frequency identification (RFID) software, that sits between the readers and the enterprise/business applications. The middleware has several functions and plays a major role in RFID system operation and management. The middleware not only manages RFID readers and printers and communicates between these devices and your business applications but also manages, filters, aggregates and makes sense of the data coming from the RFID tags.
Problems of security and privacy of RFID:
The following problems that occur with RFID cards and readers identified as follows:
1- Contents of an RFID Tag Can Be Read after the Item Leaves the Supply Chain:
RFID cards cannot be a different value from the reader to another. Since the RFID reader be mobile and RFID cards can be read from a distance of several inches to several yards, opening the field to see what are the contents of the purse or pocket when you are moving in the street, can also fire the RFID card after leaving the main center.
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