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Radio Frequency Identification (RFID)

Paper Published, National Level Paper Presentation, University of Rajasthan, 2005.

 

Why do we care? A couple of reasons, for one, this technology is being driven by eclectic mix of researchers and businessmen of Indian origin who give new meaning to the phrase ‘Made in India’. RFID is not only a huge opportunity for exporting services and software, but also a technology that can modernize India’s antiquated supply chain infrastructure.

 

Radio Frequency Identification (RFID) is the technique of giving things unique ID and then spotting them using the radio waves. It is an inexpensive technology that contains information, which can be programmed and retrieved using a reader through contact less communication. The main advantages of this technology are hands free operation; write ability, security, no need for intrinsic energy source and adaptability. It has the capability to reduce costs associated with a company’s supply chain.

 

RFID systems are being deployed in the areas like security and access control, supply chain optimization, anti-counterfeiting and asset tracking.

 

WHAT IS RFID?

 

Over the years, Indian IT companies have built big businesses by doing simple, but not necessarily easy, things like body shopping, Y2K and business process outsourcing. Now they have set their sights on yet another simple thing: Radio Frequency Identification (RFID).

 

RFID is disarmingly simple. It is the technique of giving things unique IDs and then spotting them using radio waves. It is the next step after bar coding, which has revolutionized the retail industry. Let’s look at bar codes first. The barcodes revolutionized the retail industry two decades before. Yet barcodes have many problems. The user has to be present near the tag during the identification process. They can be used only when there is line of sight with the code. Bar codes can be used only one at a time. And, worst of all, bar code do not contain much useful data. For example, all Pepsi bottles of certain size in a store will have same bar code. Unlike bar codes, each RFID tag is unique. To take the same example, each bottle of Pepsi will have different RFID tag. Such coding has tremendous utility. It can help in automatic counting, for instance. The only other way to know how many bottles there in a loaded truck is by counting manually. Manufacturers can, through a network, track their goods well into the retail store and take actions if there is a contingency, like withdrawing all the bottles that went in a particular truck.

 

RFID has at its heart a small inexpensive chip that contains information, which can be programmed and retrieved using a reader through contact less communication. In a highly networked world, RFID has the capability to reduce costs associated with companies supply chain.

 

THE TECHNOLOGY

 

RFID technology is based on bi-directional radio frequency communication between a base station and an ID tag or badge attached to a person or object to be tracked. The base station consists of a PC, or some other microprocessor system equipped with a read/write unit. The tag consists of an antenna, some control circuitry, and memory in which ID information is stored. The memory may be read only, i.e. the information stored in it is unalterable, or read/write, i.e. the information can be overwritten or added to the memory by the user.

 

 A basic RFID system consists of three components

  • An antenna or coil

  • A transceiver (with decoder)

  • A transponder (RF tag) electronically programmed with unique information

 

The antenna emits radio signals to activate the tag and read and write data to it. Antennas are the conduits between the tag and the transceiver, which controls the system’s data acquisition and communication. Antennas are available in a variety of shapes and sizes; they can be built into a doorframe to receive tag data from persons or things passing through the door, or mounted on an interstate tollbooth to monitor traffic passing by a freeway. The electromagnetic field produced by an antenna can be constantly present when multiple tags are expected continually. If constant interrogation is not required, a sensor device can activate the field.

 

Often the antenna is packaged with the transceiver and decoder to become a reader (interrogator), which can be configured either as a handheld or a fixed-mount device. The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone, it detects the reader’s activation signal. The reader decodes the data encoded in the tag’s integrated circuit (silicon chip) and the data is passed to the host computer for processing.

 

RFID tags come in a variety of shapes and sizes. Animal tracking tags, inserted beneath the skin, can be as small as a pencil lead in diameter and one-half inch in length. Tags can be screw –shaped to identify trees or wooden items, or credit card shaped for use in access applications. The anti-theft hard plastic tags attached to merchandise in stores are RFID tags. In addition, heavy duty 5 by 4 by 2-inch rectangular transponders used to track inters modal containers or heavy machinery, trucks and railroad cars for maintenance and tracking applications are RFID tags.

 

THE TAGS

 

RFID tags are categorized as:

 

Active RFID tags are powered by an internal battery and are typically read/write, i.e., tag data can be rewritten and/or modified. An active tag’s memory size varies according to application requirements; some systems operate with up to 1 MB of memory. In a typical read/write RFID work-in-process system, a tag might give a machine a set of instructions, and the machine would then report its performance to the tag. This encoded data would then become part of the tagged part’s history. The battery-supplied power of an active tag generally gives it a longer read range. The trade-off is greater size, greater cost, and a limited operational life (which may yield a maximum of 10 years, depending on operating temperatures and battery type).


 

Passive RFID tags operate without a separate external power source and obtain operating power generated from the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. The trade-off is that they have shorter read ranges then active tags and require a high-powered reader. Read-only tags are typically passive and are programmed with a unique set of data (usually 32 to 128 bits) that cannot be modified. Read-only tags most often operate as a license plate into a database, in the same way as linear barcodes reference a database containing modifiable product-specific information.

 

Semi Passive RF tags: Unlike totally passive RF tags, semi passive tags are powered by a battery, allowing for a greater read range. Powered by small batteries similar to those found in watches, semi passive tags can be used to monitor inputs from censors, even when the tags are not present in radio frequency field. Semi passive RF tags can also control outputs. These can activate or deactivates items remotely, and hence are ideal for alarm, ammunition or thermostat applications. The increased range, combined with the ability to individually read multiple tags at the same time with a single interrogation device, makes semi passive RF tags an ideal tool for efficient inventory control.

 

RFID ANTENNAS

 

RFID Antennas connected to the RFID reader, can be of various 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. RFID Antennas are devices which use radio waves to read and write data to the Tags/Labels/PCBs. Some systems use separate RFID Antennas and Controllers, while other systems integrate the Antenna and Controller into a single Reader or Reader/Writer.

 

RFID Antennas can be found in all shapes and sizes, including Antennas which can fit into very tight spaces and larger Antennas for greater read/write ranges. In addition, the Antennas provide unique solution features. One such example is the submersible Antennas used for media disc drive applications. The RFID Antennas are mounted under deionized water to read/write data to the Tags while submerged. Other examples include Antennas that offer portals around conveyors or even dock doors. These portals (also called tunnels and gates) read or write to Tags/Labels/PCBs as they pass through.

 

RFID Antennas emit radio waves that activate RFID tags as they pass through the activation field. After a tag is activated, it can send information to or receive information from the coupler. In a basic RFID system, RFID Antennas and couplers are used to read the tags affixed to each item in your collection. RFID Antennas are installed at entrance and exit lanes that communicate by radio frequency with RFID tags that are mounted in each vehicle. The system sends the tag number to a computer database for verification. It takes only a few seconds to verify access and open the gates. RFID Antennas can be placed on walls, shelves and doorways. Not only can they read the RFID tags that pass by, but they can also electronically add brand new data to the tag, such as shipping date, arrival date, and condition.

 

New Ink for Printed RFID Antennas: It may be a decade or more before conductive inks replace silicon chips, but printed RFID Antennas are much closer at hand. Today, most RFID Antennas are made from metals. Acid is often used to etch away some material to improve conductivity. That results in hazardous waste, an extra step in the process of creating an RFID tag, and additional costs. A number of companies are working on developing techniques for printing RFID Antennas using conductive inks.

 

Advantages of a printed RFID Antenna:

  • Lower cost

  • Environmentally friendly

  • Greater antenna flexibility

  • In 900 MHz products, the performance of a printed antenna is equal to traditional copper-etched antennas

 

In the venue itself, which contains gallery and performance spaces, RFID Antennas read tags in the participants’ tickets, linking their physical presence to the database records? Because RFID Antennas can be embedded into many objects, including plastic cards, and still be detected, data is protected from the wear and tear of everyday use and environmental elements. Depending on the power of the reader, RFID Antennas can be read from direct contact up to 20 feet.

 

RFID Antennas gather or add information to tags using radio wave transmission. For this reason, RFID antennas are also known as "read/write heads." The specifications of an antenna are dependent on space constraints, read range, and data throughput requirements.

An extension to Electronic Access Control is Electronic Asset Tracking and Protection Systems. These systems monitor the movement of an identified asset within a facility. Identified assets are physically tagged with a Radio Frequency Identification Device (RFID) device. RFID Antennas that are placed at various locations throughout a facility, typically at entrances, read these devices and record their movement through the protected portals. The RFID Antennas identify the RFID tag when it comes in close proximity to it. The system then determines whether the asset is authorized to leave the specified area based upon assigned parameters. Assets can also be assigned to individual access control cardholders. The system can then determine if a particular individual is authorized to remove an asset from a secured area. Alarms can be generated, and operators notified of any unauthorized movement of an asset. Asset Tracking Systems can also be used to determine the location of a selected asset within a facility.

 

RFID-Antennas - mainly loops - are very-very small compared to the wavelength (about 300m) resulting in a very-very poor efficiency in the far field (long distance). RFID antennas are developed to generate a magnetic near field primarily. Unfortunately, the near field (which always surrounds an antenna in the range up to wavelength / 16 => about 300m @ 125 kHz) decays with 60dB per decade - so ten times the distance resulting in 1/1000000(!) of the received power. Reaching the far-field (distance to antenna > 300m) the decay drops to only 20dB per decade (ten times the distance resulting in 1/100 of the received power). 

 

RFID CIRCUITS

 

The high integration of RFID Circuits allows a relatively easy implementation into any customer specific application. RFID Circuits are printed on a custom designed screen press with conductive inks.

 

In older systems, a fixed base station transmitter interrogates the vehicle transceiver, which sends its ID in response. Such active systems are bulky and expensive. But today, a new generation of RFID systems has emerged. They use a fully passive receive/transmit unit called a tag or transponder in the vehicle to respond to external interrogation. These RFID tags are small and flat, and they require no battery power. An RFID tag in RFID Circuits is as easy to attach to the windshield as an inspection sticker.

 

The tag consists of a resonant circuit tuned to 125 kHz, 134.2 kHz, 13.56 MHz, 915 MHz, or 2.4 GHz. The signal transmitted by the base station is detected, and the RF output developed in the tuned circuit is rectified into a dc voltage that powers a small transmitter which sends a coded signal back to the base station. A read range of up to several meters is possible with high enough power and a good antenna. An on-chip Flash memory contains the ID code. Such tags run under $10. Major manufacturers of RFID Circuits and equipment are the Amtech Division of TransCore Inc., Microchip Technology Inc., and Texas Instruments.

 

In 1989, it was noticed that RFID Circuits will bring about new RF applications in logistics. Radio Frequency Identification or RFID tags make it possible to identify individual products by using wireless RF signals. At high frequencies (e.g. at 900 MHz) tags can be read from a distance of a few meters. RFID Circuits can convey logistic and measurement information, & do not require power sources of their own.

 

The RFID Readers are powerful tool for obtaining information emitted by RFID tags in RFID Circuits. RFID tags are placed inside, or on, a variety of items depending on the system's purpose. The tags contain information and the amount and complexity vary depending on the type of tag. RFID Readers or scanners are able to retrieve the tag's information and change it if capable. RFID solutions are used by different industries, and for variant purposes. Digital RFID readers can pick up the signal from several feet away, so workers don’t have to manipulate the items to read them.

RFID Readers use Time Division Multiple Access, or TDMA, meaning they read tags at different times to avoid interfering with one another. RFID Readers in RFID Circuits have already been experimentally embedded into floor tiles, woven into carpeting and floor mats, hidden in doorways, and seamlessly incorporated into retail shelving and counters, making it virtually impossible for a consumer to know when or if he or she was being "scanned."

  

FREQUENCY RANGES

 

Low-frequency (30 KHz to 500 KHz) systems have short reading ranges and lower system costs. They are most commonly used in security access, asset tracking, and animal identification applications. High-frequency (850 MHz to 950 MHz and 2.4GHz to 2.5 GHz) systems, offering long read ranges (greater than 90 feet) and high reading speeds, are used for such applications as railroad car tracking and automated toll collections. However, the higher performance of high-frequency RFID systems incurs higher system costs.

 

The significant advantage of all types of RFID systems is the non-contact, non-line-of-sight nature of the technology. Tags can be read through a variety of substances such as snow, fog, ice, paint, crusted grime, and other visually and environmentally challenging conditions, where barcodes or other optically read technologies would be useless. RFID tags can also be read in challenging circumstances at remarkable speeds; in most cases responding are less than 100 milliseconds. The read/write capability of an active RFID system is also significant advantage in interactive applications such as work-in-progress or maintenance tracking. Though it is a costlier technology (compared with barcode), RFID has become indispensable for a wide range of automated data collection and identification applications that would not be possible otherwise.

 

Developments in RFID technology continue to yield larger memory capacities, wider reading ranges, and faster processing. It is highly unlikely that the technology will ultimately replace barcode – even with the inevitable reduction in raw materials coupled with economies of scale, the integrated circuit in an RF tag will never be as cost-effective as a barcode label. However, RFID will continue to grow in its established niches where barcode or other optical technologies are not effective. If some standards commonality is achieved – whereby RFID equipment from different manufacturers can be used interchangeably - the market will very likely grow exponentially.

  

COMMON APPLICATIONS

 

Transportation/distribution: As suggested earlier, RFID systems are uniquely suited for use in the rigorous rail environment. Field programmable tags permit the full industry standard 12-character identification of each car by type, ownership and serial number. Tags are attached to the vehicle undercarriage; antennae are installed between or adjacent to the tracks and readers or display devices are typically located within 40 to 100 feet in a wayside hut along with other control and communication equipment. A primary objective in rail applications is the improved fleet utilization that permits reductions in fleet size and/or deferral of investment in new equipment.

Commercial truckers are using RFID systems to monitor access and egress from terminal facilities. Combined with weigh-in-motion scales, the same systems can be used for transaction recording at the refuse dumps recycling plants, mines and similar operations, or for credit transactions at truck stop or service depots.

 

Industrial: In the plant environment, RF systems are ideally suited for the identification of high-unit-value products moving through a tough assembly process (e.g., automobile or agricultural equipment production where the product is cleaned, bathed, painted and baked). RF systems also offer the durability essential for permanent identification of captive product carriers such as Tote boxes, containers, barrels, tubs, and pallets, Tool carriers, monorail and power, and free conveyor trolleys.

 

Security and access control: The movement and use of valuable equipment and personnel resources can be monitored through RF tags attached to tools, computers, etc. or embedded in credit-card-size security badges. This type of monitoring also provides an extra measure of security for personnel working in high-risk areas in case of an emergency evacuation.

 

Animal identification: Valuable breeding stock, laboratory animals involved in lengthy and expensive research projects, meat and dairy animals, wildlife, and even prized companion animals all present unique identification problems that can be solved by innovative applications of RFID technology

  

Some other primary applications

 

Direct product identification wherein the tag specifically identifies the item to which it is attached (e.g., by part number or serial number or, in case of read/write systems, assembly or process instructions for the item).

 

Carrier identification where content is identified manually (or with bar code reader) and fed to the control system along with the carrier’s machine-readable RF ‘license plate number’. Strategically deployed RF readers accomplish subsequent load tracking.  The automotive industry uses RFID systems to track vehicles through assembly, where tags must perform even after repeated subjection to temperatures of 150 to 200 C, painting, etc. A primary objective for use of the technology in this environment is verification of vehicle identity prior to execution of given assembly tasks. Although manufacturers sequentially track vehicles through assembly, undetected removal of a single vehicle from the line could be costly.

 

For reading, RFID tags need not be ‘seen’, they can be buried within pallets, tote boxes and other containers and provide solid performance for the life of the carrier. As an example, in casting operation RF tags are attached to wire baskets which travel through a variety of degreasing, etching and cleaning tanks by means of an overhead power and free conveyor – not a job for optical or magnetic identification media. In a manner similar to carrier identification, RF tags can be used for tool management. Miniature tags can be placed within tool heads of various types such as block or Cat V-flange, or even within items such as drill bits where individual bits can be read and selected by reader guided robot arms.

RFID systems are used for lift truck and guided vehicle identification in a number of installations. One approach buries tags at strategic locations throughout the facility and verifies vehicle location via on-board DC-powered readers. Other users station readers at the ends of warehouse aisles to monitor lift truck activity. Here, throughput rates permit multiplexing multiple antennae per reader.

  

ADVANTAGES

 

  • Hands free operation: There is no need to insert the tag or badge into a reader as in case of magnetic or smart cards. This is particularly advantageous in moving environments such as buses or trains. Operation is faster as no time is spent in front of a reader or machine.

 

  • Writability: The write capabilities of tags are particularly advantageous for access control applications. By writing each accessed location into the tag’s memory, an audit trial of the person or object can be kept. Write ability also allows tags to be reused for different applications.

 

  • Security: The information contained in the tag may be protected through the use of passwords. This ensures a much higher level of security than bar codes or magnetic cards.

 

  • ·No need for intrinsic energy source: The absence of batteries or other intrinsic energy sources within passive tags allows for their long life and ecological use.

 

  • Adaptability: Tags may be adapted to various environments, made in different sizes and shapes, and encapsulated in different materials such as plastic and aluminum.

   

LIMITATIONS

 

Certain wavelengths, such as 2.4 GHz, are absorbed by water. This causes read/write problems. A large no of metal near tag also causes interference, so shielding and positioning of tags is important in manufacturing environments, which adds to their cost limits usefulness. Also, the cost of tags is still three times the cost of a conventional baggage tag or a hundred times the cost of a simple bar code label.

   

CONCLUSION

 

Now that standards are starting to appear, RF identification will rapidly expand. As a result, the cost of tags will reduce over time. Industry experts predict substantial growth in this market. RFID will be the next technological wave for the automatic data capture industry.


This paper, originally submitted in 2005, secured second prize at the national level competition, which included participation from national universities, IITs, and other premier institutes.


Published by: Gaurav Mathur and Abhishek Malav

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