RFID Technology

Introduction

Radio Frequency Identification, or RFID, is a sensor technology by which a remote transponder (an RFID tag) communicates with an interrogator (an RFID reader) via radio through intervening materials (with limitations of course), without line-of-sight restrictions, and without operator interaction. RFID is used for a huge variety of sensor-based tracking applications.

RFID applications are categorized by the frequency at which the application operates, as shown below. Notably, the frequency bands governments allocate differ from country to country. The UHF band is most widely available.

Description	Frequency	Application
Low Frequency (LF)	125 kHz to 134 kHz	Electronic article surveillance (shoplifting prevention). Very low data rates and small payload, often only one bit.
High Frequency (HF)	13.56 MHz	Low data rates, small payload, short distance, good object penetration
Ultra-High Frequency (UHF)	400 MHz to 930 MHz	High data rates, large payload, medium distance, good object penetration, standards
Super-High Frequency (Microwave)	2.45 GHz, 5.8 GHz	High data rates, large payload, large distance, good object penetration, emerging technology, mostly active

Tags (Transponders)

An RFID tag is composed of an inlay and an encapsulation. The inlay is a film-like substrate or a circuit board on which an antenna and RFID integrated circuit (RFIC) are attached. The RFIC contains a radio frequency interface component, a memory component, and a logic control component.

Encapsulation takes many forms. Small passive inlays can be encapsulated in standard printer labels and stick-on carriers. Encapsulation can facilitate permanent mounting, and can tune the RF profile of the inlay for different materials like cardboard, metal, or glass. Also, encapsulation can protect the inlay so that it can survive wet, high temperature, or corrosive environments.

Readers (Interrogators)

Like RFID tags, RFID readers come in a variety of form factors for different applications.

Reader Type	Usage
Fixed	Fixed readers have multiple antenna ports, often four or more, and transmit at the maximum allowed power. Fixed readers often have external input/output ports to interface with sensors and stack-lights. These readers are used as portals, industrial stations, controllers, etc. They read large numbers of tags simultaneously, and have sophisticated algorithms for avoiding tag collisions, finding weak tags, and minimizing interference from near-by readers. Fixed readers can run complex workflows onboard, or be controlled over the network by remote servers.
Hand-held	As computer power and battery life have increased and RFID readers themselves have improved, it has recently become practical to incorporate a rugged antenna into a hand-held scanner platform. These readers open up a range of application possibilities by extending business workflows to more isolated sites. By the same token, the disconnected nature of mobile platforms creates new issues obtaining and updating data. Hand-held readers are usually customized with local work flow programs.
Vehicle Mounted	Vehicle mounted readers are made practical by the same technology trends influencing hand-held readers. Often vehicle mounted readers have a built-in antenna directed in a forward orientation and an optional antenna directed in a downward or sideward orientation. These readers run off 12 volt power and can withstand the rigors of a plant, factory, or warehouse environment.
Printer	Printer readers were developed to encode RFID labels. They are fitted in a label printer and controlled via extensions to the printer vendor's label print control language. When the label is printed the printer advances to the embedded tag position, the tag is encoded, and then the human-readable data is printed. Because the antenna can be in very close proximity to the tag power requirements are low. Also, reader logic can be simplified to deal with just one tag at a time.
Utility	Utility readers have entered the market as simple reader/antenna combinations based on printer readers and mounted in small handy enclosures. These readers can be controlled and powered from a laptop over USB, and facilitate many RFID utility functions, like commissioning tags, verifying tag encodings, and quickly reading single tags.

RFID Data Standards

The body that administers RFID standards is EPCglobal. EPCglobal manages RFID standards much like Universal Product Codes (UPC) codes have been managed for barcode applications. EPCglobal standards for passive RFID tags cover two general areas: the definition of the "air protocol," or how interrogators and tags communicate amongst themselves, and the structure or encoding of data on the tag. While the operation of the air protocol is vital—controlling such functions as collision avoidance, filtering, and quiescience—it is usually not a concern for RFID application development. Tag encoding, however, is very much a part of RFID application development.

Until late 2004 there were many proprietary encodings for passive RFID tags promoted by a number of manufacturers. These tag types, now referred to as Generation 1, were divided into classes like 0, 0+, and 1, according to their payload and write-ability. One of the most significant developments in RFID this decade has been the emergence of standards for passive RFID tags. The standard defines a predominant second generation tag type called Class 1 Generation 2, or C1G2. The international standards organization designation for the C1G2 standard is ISO-18000-6B. As C1G2 tags have become prevalent Generation 1 tags have fallen out of use and have become difficult to procure.

An RFID tag is designed around a payload—the tag data memory. C1G2 memory is read/write, although writing a tag takes about three times longer than reading and is often less reliable under field conditions. Not all C1G2 tag memory is writable. A C1G2 payload is divided into banks, as illustrated below.

Memory Bank	Description	Usage
0	Reserved	Contains passwords for functions like memory locking and disabling
1	EPC ID	Primary data bank containing the writable EPC Identifier, as described below
2	Tag ID (TID)	Contains manufacturer identification codes and some control data; not a unique identity
3	User Data	Tag fabricators may provide user-defined memory; not yet in common use

The EPC Identifier, found in Bank 1 of the C1G2 tag memory, is the primary piece of read/write data on a C1G2 tag. The most standard format of the EPC ID is defined to be 96 bits, or twelve bytes. The most recent EPCglobal specifications allow for some formats to be as long as 202 bits, but these formats are not in common use.

While any data within length limitations can be encoded on a C1G2 tag, EPCglobal defines several standard encodings, called tag identities, that all parties can interpret meaningfully. Tag identities are used in specific situations for different tracking applications, and can be used together for some applications.

The encoding for each tag identity is divided bit-wise into fields. When the EPCglobal encoding rules are applied properly, the tag identity fields altogether make each tag absolutely unique. This means that a physical asset can be tagged, uniquely identified, and tracked amid large numbers of similar assets.

Tag Identity	Usage
Serialized Global Trade Item Number (SGTIN)	The SGTIN is the serialized form of the EAN.UCC GTIN code; as such, an SGTIN tag uniquely identifies the asset to which it is affixed. SGTIN tags are often used to track cartons and pallets in the supply chain.
Serial Shipping Container Code (SSCC)	The SSCC is the EAN.UCC SSCC code. An SSCC tag identifies a shipping container in the supply chain, and often is used for pallet tracking.
Serialized Global Location Number (SGLN)	The SGLN is an identifier of physical or legal entities. An SGLN tag often is used as a beacon tag for a discrete, unique physical location such as a dock door or bin, or an aggregate physical location such as an entire warehouse.
Global Returnable Asset Identifier (GRAI)	The GRAI is an identifier of individual long-lived objects. A GRAI tag often is used to track fixed assets in buildings, or work-in-process inventory in factories and warehouses.

Passive Versus Active

Passive RFID uses tags that have no internal power source—they absorb and reflect power from the radio field emitted by the RFID interrogator. Consequently passive read ranges are somewhat limited: six to fifteen feet depending on equipment and environment. Passive tags carry small data payloads—often 128 to 256 bytes. Passive tags are manufactured in large quantities—in volume a passive inlay costs less than $0.10. Passive tags also can be very small.

Active RFID uses tags that carry a battery. Active tags have much greater read ranges—600 feet or more—and can carry 2KB or more of data, and incorporate temperature and other sensors. Because of the battery and other components active tags are larger than passive tags, and more expensive—$20 to $120. Furthermore, data standards like the well defined EPCglobal passive RFID standards, are still evolving for active RFID.

Passive Tags

Using advanced radio frequency technology, passive tags can receive data at distances of up to three meters (nine feet) from either a handheld or fixed interrogator.

A unique feature of our tags is a highly sophisticated anti-collision handling algorithm that allows simultaneous communication with hundreds of tags within the interrogator's read zone. We carry many sizes and shapes of passive tags to support your application and its requirements.

Readers for Passive Tags

Our passive readers provide RFID capabilities in most frequency bands and capable of supporting applications in supply chain, work in process, manufacturing and retail operations. The readers are designed to provide cost effective solutions with special versions for programmable logic controllers (PLC) supporting both the RS232 and RS422 communication requirements. With up to four antenna ports, you can provide greater coverage thus reducing your cost per data collection zone.

Antennas for Passive Readers

We offer a wide range of antennas to provide you the coverage and functionality needed for your RFID installation. We specialize in both directional and omni-directional antennas with the required cables to provide your data collection system the power it needs.

Passive Tag Encapsulation

The encapsulation of Passive RFID tags performs several very valuable functions, including protection from the environment and business processes, and creating the necessary offsets required to mount on metal. Of particular importance is that the packaging must be compatible with the radio frequency (RF) performance of the tag. Tags can be de-tuned if packaged incorrectly, degrading RF signal performance. This causes tag detection range to be reduced, or even destroyed. Entigral Systems has worked with radio frequencies specialists to create for you the right tag with the right frequency to give you the right read range.

Active Tags

Using advanced UHF radio frequency technology, active tags transmit and receive data at distances of up to 100 meters (300 feet) from either a handheld or fixed interrogator.

A unique feature of our tags is a highly sophisticated anti-collision handling algorithm that allows simultaneous communication with thousands of tags within the interrogator's read zone.

Because of its low power consumption, the tag can effectively operate for over five years. Also, the LED supports visual recognition, suitable for pick-to-light applications. Our special tags, with their credit card design, are very economical and ideal for tracking large numbers of assets or personnel.

Readers for Active Tags

Our active RFID readers allow the seamless integration of tag information with a host computer system. The result is real-time information, where and when it is needed.

Our readers have the ability to listen with up to four antennas concurrently where the tag's signal is received by all antennas at exactly the same time. This feature allows fast and reliable identification of tags. Additionally, the built-in signal strength measurement capability enables the localization of tags using triangulation. An internal real-time clock provides accurate time stamps for data captured from the tags. A maximum of 2,000 messages can be stored on the reader to prevent data loss. These feature-rich readers, combined with other system components, offer a leading-edge wireless, automated data collection tool that is easily integrated into a wide variety of applications.

Antennas for Active Readers