In general terms, Radio Frequency IDentification (RFID) is a means of identifying a person or object using a radio frequency transmission, typically 125kHz (Low Frequency), 13.56 MHz (High Frequency) or 800-900MHz (Ultra High Frequency). RFID has been in existence for more than 20 years, and it has been extensively used in applications such as toll collection, access control, ticketing, and car immobilization devices (also called immobilizers). In recent years, the technology has received increased attention due to a confluence of actions including technology advancement, heightened security concerns, supply chain automation, and a continuing emphasis on cost control within industrial systems.

The primary benefit of RFID tags over barcodes is their ease of use and reliability. RFID tags can be read or written to at longer distances of up to several feet, while in motion, in any orientation, through intervening objects and without the need for line of sight. RFID tags enable reliable automation while barcodes are better suited for manual scanning. Perhaps, most significant, is the fact that several RFID tags can be read simultaneously and automatically, while barcodes have to be scanned one by one.

• Readable without visibility (line of sight)
• Bulk identification: Fast and simultaneous reading of several tags
• Data modifiable (optional): Read / Write ability
• Robust system without moving parts: durable, reliable and trouble-free disposal
• Global standards (SCM): Unique ID-code
• Integrated functionalities possible (EAS, EMV, etc.)

An RFID tag contains a chip attached to an antenna ("inlay”). RFID tags are developed using a frequency according to the needs of the system including read range and the environment in which the tag will be read. Tags are either active (integrating a battery) or passive (having no battery). Passive tags derive the power to operate from the electro-magnetic field generated by the reader.

A Chip-based RFID tag contain silicon chips and antennas. The response of a passive RFID tag is not necessarily just an ID number; the tag chip can contain non-volatile EEPROM for storing data. Major supplier of chips are NXP/Philips, Texas Instruments, Infineon, Hitachi, etc.

A RFID antenna connected to the RFID reader, can be of varying size and structure, depending on the communication distance required for a given system's performance. The antenna activates the RFID tag and transfers data by emitting wireless pulses.

A RFID reader can be fixed or handheld, and is usually connected to Management Information System or Personal Computer. The RFID reader handles the communication between the Information System and the RFID tag.

A RFID station is made up of an RFID reader and an antenna. It can read information stored in the RFID chip and also update this RFID tag with new information. It generally holds application software specifically designed for the required task. RFID stations may be mounted in arrays around transfer points in industrial processes to automatically track assets as they are moving through the process. 

Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit in the tag to power up and transmit a response. Most passive tags signal by backscattering the carrier signal from the reader. This means that the antenna has to be designed to both collect power from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not necessarily just an ID number; the tag chip can contain non-volatile EEPROM for storing data.

The lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded in a sticker, or under the skin in the case of low frequency RFID tags.

The lowest cost EPC RFID tags, which are the standard chosen by Wal-Mart, DoD, Target, Tesco in the UK and Metro AG in Germany, are available today from SmartCode at a price of 5 cents each.The addition of the antenna creates a tag that varies from the size of a postage stamp to the size of a post card. Passive tags have practical read distances ranging from about 10 cm (4 in.) (ISO 14443) up to a few meters (EPC and ISO 18000-6) depending on the chosen radio frequency and antenna design/size. Due to their simplicity in design they are also suitable for manufacture with a printing process for the antennas.

Passive RFID labels or tags are the cheapest and most commonly used in the market. Like barcodes, passive tags send unique encoded digital numbers back to the reader. The process starts by the absorption of electromagnetic energy by the antenna, which is used to activate the electronic chip. After activation, the chip modulates the backscattering reflectivity properties of the antenna, and as a result, the reflected energy is returned to the reader as a binary code of information. This reflects the unique number programmed in to the chip, identifying the specific labeled product. From this, we can see that the metallic antenna has two roles:

• To absorb enough electromagnetic energy to activate the bonded chip
• To be an efficient reflector for the electromagnetic radiation emitted by
  the reader

Unlike passive RFID tags, active RFID tags have their own internal power source which is used to power any Integrated Circuits that generate the outgoing signal. Active tags are typically much more reliable (e.g. fewer errors) than passive tags due to the ability for active tags to conduct a "session" with a reader. Active tags, due to their onboard power supply, also transmit at higher power levels than passive tags, allowing them to be more effective in "RF challenged" environments like water (including humans/cattle, which are mostly water), metal (shipping containers, vehicles), or at longer distances. Many active tags have practical ranges of hundreds of meters, and a battery life of up to 10 years.

Some active RFID tags include sensors such as temperature logging which have been used in concrete maturity monitoring or to monitor the temperature of perishable goods. Other sensors that have been married with active RFID include humidity, shock/vibration, light, radiation, temperature, and atmospherics like ethylene. Active tags typically have much longer range (approximately 100 m/300 feet) and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver.

The United States Department of Defense has successfully used active tags to reduce logistics costs and improve supply chain visibility for more than 15 years. At present, the smallest active tags are about the size of a cold capsule and sell for a few dollars.

• Contactless Smart card
  A smart card, chip card, or integrated circuit card (ICC), is defined as any pocket-sized card with embedded integrated circuits which can process information. This implies that it can receive input which is processed - by way of the ICC applications - and delivered as an output. There are two broad categories of ICCs. Memory cards contain only non-volatile memory storage components, and perhaps some specific security logic. Microprocessor cards contain volatile memory and microprocessor components. The card is made of plastic, generally PVC, but sometimes ABS. The card may embed a hologram to avoid counterfeiting.
  
  

  Examples of Vicinity Smartcards:
  - Transport payments
  - Biometric Passports

• Pallet & Case Tracking 

  Pallet and case tracking involves tagging bulk packaged items (i.e. a box of goods, not the individual units of sale), usually at the manufacturing source.  The implementation of pallet and case RFID tracking is anticipated to bring further efficiencies in the supply chain, from packaging, through shipping and distribution, and into the back-end of the retail store or final distribution point. Benefits are expected to arise from improved control, reduced touch and reduced diversion. Pallet and case tracking is largely being driven by the mandate of several large retailers such as Wal-Mart in the US and Tesco in Europe, as well as by the US DoD. As noted above, UHF is the preferred solution as it allows for longer read ranges.
  
  

  Examples:

  - Supply Chain Management

  - Container / pallet / case tracking

  - Automotive: Electronic Toll Collection

   

• Item-level tracking

  Individual items are tagged at the manufacturing place, in a warehouse, or by the operator of a closed loop system such as a library. Tags are read in bulk, often through a container (box, bag, etc.), along a process line or in the supply chain, and without a line of sight. Performance demand is very high (above 99.95% read rate in bulk). Implementation is being driven by both value considerations as well as by mandates from government agencies and customers.  Benefits are shared between the retailer, the wholesaler, the manufacturer, and other participants in the supply chain.

   

  Examples:

  - Libraries
  - Textile rental
  - Pharmaceutics
  - Patient identification
  - Ticketing