What does an RFID system consist of?
An RFID system consists of several components including one or more contactless memory tags (or transponders) attached to the items to be labeled, identified and traced, and handheld or fixed contactless read/write reader station units or coupling devices exchanging data with the transponder(s) by means of RF signals.

Contactless memory tags (transponders) are the backbone of the RFID system since they contain the data that identify the items. A contactless memory tag is made of a non-volatile memory associated with a radio-frequency communication block that performs RF signal modulation, demodulation, and power supply regulation, and an antenna. A transponder can be read-only (ROM), one-time-programmable (OTP), or read/write (EEPROM), and it can be embedded in various package formats (such as inlays, cards, and buttons).

The reader (or reader station unit) is connected to the antenna that transmits and receives the radio-frequency signal to and from a transponder. The reader sends an RF signal to the transponder’s antenna. This signal generates a voltage that is rectified and provides a power source to the transponder. The power is transferred from the reader to the transponder through an inductive coupling between the two coils in 125 kHz and 13.56 MHz systems. For ultra-high frequencies (UHF), the electric field generated by the reader is used to power the tag. In other words, the transponder does not need a dedicated power supply.

During the reader-transponder communication, the RF signal generated by the reader is modulated according to the data to be sent. In the transponder-reader direction, no modulation is applied on the reader RF signal and the communication is done through load modulation in inductive coupling systems. The reader interfaces with the RFID system control host through a serial interface such as RS232, RS422/485, or USB.

TECHNICAL PRINCIPLES
Anti-collision mechanism
The anti-collision mechanism allows the reader to detect and identify all transponders in its operating range and individually access each one of them. Each transponder is uniquely identifiable by its dedicated unique ID (UID). Transponders that are not equipped with the anti-collision mechanism can only be accessed one at a time. Transponders can only respond to incoming requests and the communication is based on the concept of reader talks first. The reader sends a request to all transponders in its operating field. This inventory message prompts the transponders to respond using the method presented above. When are multiple transponders around, they all understand the message coming from the reader and are obliged to respond. If they all answer at the same time, their replies corrupt each other, and the reader is not be able to decipher them. To cope with this, an anti-collision mechanism has been implemented. In ISO 15693, for example, a slot-marker mechanism is enabled, based on a transponder UID and an application family identifier (AFI). In case when only a smaller number (up to 50) of transponders needs to be uniquely selected, simpler algorithms can be used, such as a system based on a chip identification number (Chip_ID) in ST’s short-range products. In UHF, the data-matching mechanism is based on the EPC (electronic product code) numbering scheme.

Unique identifier (also tag ID or TID)
In ST’s contactless memory products, the UID is typically a 64-bit identifier that can be used by an anti-collision algorithm, such as the ISO 15693 standard. The UID enables unique identification of a large number (from fifty to thousands) of transponders in the reader field. The UID is programmed in the transponder during the manufacturing process and can never be changed afterwards. In ISO 15693, the reader sends out an inventory request and performs the transponder-identification sequence in a deterministic way. Each transponder sends back its UID to identify itself to the reader.

Chip identifier or chip_ID
The chip_ID is typically an 8-bit handle used by the anti-collision algorithm in ST’s short-range family products. The Chip_ID enables unique identification of a small number of transponders in the reader field. This identifier is either programmed by the transponder issuer or generated by the transponder itself upon entering the reader field.

Application family identifier or AFI
In ISO 15693, the AFI describes the type of application targeted by the reader. This identifier is used to extract all transponders in the reader field that meet the required application criteria. After the reader sends out the AFI, only the AFI-compliant transponders of the appropriate family will respond.
Programmed by the transponder issuer, the AFI is read-only and its value cannot be modified.

EPC code
The EPC code is a unique item ID (UII) defined in the EPCglobal specification. It is a 64- or 96-bit code, programmed by the end customer. The EPC ID consists of a group of 3 unique codes, specifying the item’s maker, class, and its serial number. As for the bar code, EPC codes are administered and distributed to its members by EPCglobal, an organization promoting an open global standard for real-time, automatic identification of items to be managed in the supply chain.

Anti-clone function (ACF)
The ST anti-clone function (ACF) protects an application from counterfeiting by enabling the RFID system to authenticate the transponders. ST’s ACF has been successfully embedded and proven reliable in a wide range of RFID systems, including pre-payment, anti-counterfeiting, and brand-protection applications.

OPERATING RANGES AND APPLICATIONS
Close-coupling, short-range, long-range, and extended-range applications
The RFID operating ranges are defined by the distance between the transponders and the reader.

The close-coupling range covers transponder-reader distances up to 5 cm. Brand protection, anti-counterfeiting of electronic goods and food consumables, as well as electronic purchases at vending machines operate in the close-coupling range. These applications employ low-cost readers operating with a limited number of transponders and require security features such as password, anti-clone, or cryptographic capabilities.

RF systems are also a universal solution for various ticketing applications, no matter what means of transport (public transportation or private car) are used. Contactless systems can also be used in a wide range of access-control applications, including entrance systems to and within public buildings (offices), time and attendance systems, room logistics at hotels, locking systems, and amusement parks. These short-range or proximity-range applications use low-cost transponders embedded in plastic cards or paper tickets and they operate in the range up to 20 cm. Readers and transponders from different suppliers must be fully interoperable. Required security levels are satisfied through password, anti-clone, or cryptographic capabilities.

RF transponders are a low-cost universal solution for tracking a wide variety of valuable assets, such as, package delivery or animal tracking and improving supply chain management from manufacturing, through stock handling to distribution. Capable of storing traceability history, transponders provide accurate real-time information on each tagged item. Similarly, they can be used for anti-theft applications (using electric article surveillance) or access control from a longer distance.

These long-range or vicinity-range applications operate within one meter from the reader and typically involve a large number of low-cost transponders (100+), requiring reliable anti-collision mechanisms and transponder-reader interoperability.

Extended or very long-range (up to 10 meters) RFID systems will be instrumental in creating low-cost contactless solutions for new supply chain, logistics, and tracking applications that can offer improved efficiency, accuracy, and security standards to major manufacturers, retailers, and their customers.


ST STRATEGY FOR RFID AND RF MEMORY PRODUCTS
STMicroelectronics is a worldwide leader in EEPROM products, including standard memories up to 1-Mbit density, and ASMs (application-specific memories). The Company has also participated in defining the standards for contactless memory communications, including ISO 14443 type B, ISO 15693, ISO 18000, and EPCglobal.

ST offers ISO-standard and custom RFID products and helps its key customers to access and exploit the contactless application world. The Company’s current portfolio of contactless memories will be extended to match different target applications, in accordance with open standards.

Committed to high-volume/low-cost identification solutions, ST offers low-cost, standard-compliant RFID chips and complete systems through its wide partner network (reader and converter makers, inlets makers). The Company has built strong relationships with key players in this field and developed a wide variety of RFID products for applications in retail, mass transit, vending machines and many others.


CONCLUSION
Contactless tags are a universal cost-effective identification solution addressing a wide range of applications. Anti-collision capability and its ability to be read or written without a direct line of sight make this technology more efficient in comparison with currently used systems, such as paper barcodes or dot matrices. Since no item can pass by a transponder reader without being scanned and/or updated, human intervention and its associated costs are significantly reduced.

ST's experience in the contactless domain, partnerships with system integrators, and strong involvement in standardization activities have enabled the Company to develop a highly cost-efficient, flexible, and interoperable portfolio of contactless identification products.

For more information on ST’s offering in RFID visit www.st.com/rfid