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Retail RFID Systems without Smart Shelves

by Jeff Lindsay, Walter Reade, and Larry Roth

The following article was published Dec. 23, 2003 on as Article 21114D, available at

Related articles at on radiofrequency identification (RFID) technology:

Table of Contents

Retail RFID Systems without Smart Shelves

Jeff Lindsay, Walter Reade, and Larry Roth
Nov. 7, 2003


In retail stores and other environments, the inability to rapidly locate items is a common problem. Retailers may appear to be out of stock of a product, when in fact the product may be available in the back of the store or may have been placed on the wrong shelf. RFID (radiofrequency identification) technology has been proposed as a means to improve the ability to track inventory and to locate objects. In particular, the use of RFID-tagged objects coupled with smart shelves that include RFID readers has been proposed as a means of efficiently tracking the presence of products in a retail environment. However, the smart shelves that have been demonstrated in public trials have employed numerous expensive RFID readers adapted to read sections of a single shelf, and have required the use of expensive and bulky coaxial cable for each of the readers.

Improved smart shelves have been proposed in which a single antenna built into the shelf can be used to read discrete sections of a shelf, but even with these improved systems numerous readers may be needed for each of the many shelves in a store, and even then objects may be placed in regions not adjacent to a smart shelf where they may effectively disappear from an RFID-based inventory tracking system. While advances in technology promise to bring the cost of RFID scanners down substantially, the cost of numerous smart shelves may still be excessive for some applications, particularly in environments where shelves per se cannot be installed or where wired shelves may pose problems for wiring access or safety. Thus, there is a need for a system that permits tracking of objects in a retail store or other environment without the need for numerous readers and without the need for objects to be adjacent to a fixed hardwired reader. In this paper, we propose several alternative systems that may be considered.

Background: Smart Shelves

There have been several proposals for smart shelves that can use RFID technology to automatically track products on the shelves of retail stores. Some concepts are treated in PCT publication WO 00/65532, "Storage System," published Nov. 2, 2000, by Kevin Ashton, former Director of the Auto-ID Center. Smart shelf units under the name "SmartShelf" have been manufactured by SAMSys Technologies, Inc. (Ontario, Canada). Hitachi High Technology Corporation (Tokyo, Japan) has also developed a smart shelf consisting of an RFID reader with multiple antennas adapted to read Hitachi 13.56 MHz Coil-on-Chip (CoC) chips (see "Smart Shelves," Smart Packaging Journal, No. 9, May 2003, p. 7). Custom smart shelves including multiple RFID readers have also been installed and trialed in several retail stores in the US and Europe, including the Metro Group Future Store in Rheinberg, Germany (Metro AG, Düsseldorf, Germany) described in a series of animations and other files at However, these shelf units are expensive, especially in the large quantities necessary to handle the entire product inventory within a retail facility. Furthermore, these shelf units may not be suitable for end-aisle display units or for use in the storage area, where items may be stored in boxes or on pallets in a disorderly fashion.

Smart shelves in early demonstration trials in Europe and the United States have been both expensive and cumbersome, with multiple stand-alone readers installed at multiple locations along a single shelf to track items at various stations. The use of coaxial cable for these readers has resulted in cluttered equipment around the shelves. As an improvement, advanced smart shelves have been developed in which a single antenna or single array of interconnected antennas with a single reader can be used to determine the location along a shelf. One such technology is that taught by D.G. Bauer et al., "Intelligent Station Using Multiple RF Antennae and Inventory Control System and Method Incorporating the Same," US Patent Publication 200030174099-A1, published Sept. 18, 2003, filed as US patent application Serial No. 10/338892, assigned to MeadWestvaco Corporation.

Another technology for smart shelves that is said to eliminate the need for coaxial cable and provide good resolution on a shelf at low cost is the recirculating phase array antenna system of AWID (Applied Wireless Identification Group, Hollister, California) coupled with their fast look-ahead decay sensing system. Such antenna systems can be provided in roll-to-roll form for easy retrofitting of existing shelves, as discussed by AWID President, Jeffrey Jacobsen, "Low Cost, Digitally Amplified Shelf Antennas," Proceedings of the Smart Label Europe 2003 Conference (available on CD-ROM), Cambridge, England, Sept. 29-30, 2003, sponsored by IDTechEx. A film provided with the antennas and conductive leads can be provided for rapid placement on the surface of a shelf where it may be hidden under paper or other materials. Associated with the antenna system are additional electronics for signal reading and processing.

In spite of these advances, there are some situations in which smart shelves are impractical, impossible, or perhaps too expensive for effective object tracking using RFID technology. Alternatives are needed for location the position of targeted objects associated with RFID tags.

Alternatives to Smart Shelves: Extended Scanning and RFID Beacons

One approach for scanning and locating objects across long ranges without the need for nearby smart shelves is to use RFID tags with high read ranges. Typically, passive RFID tags have low read ranges at the power levels permitted by national regulations. Depending on the antenna size and frequency of operation, the tag may have a range of several centimeters to two or three meters. Thus, it is generally assumed that objects must be near a fixed scanner in order to be read in a retail environment. Further, the limitations imposed by interfering objects can also limit the read range achieved.

Were active RFID tags to be used instead, reading many tags with a few readers would be much easier, for much higher read ranges are possible. The advent of printable, low-cost batteries on paper or film, such as the batteries of PowerPaper (Einat, Israel--see or those of Cymbet Corp. (Elk River, Minnesota--see "Thin-film Battery May Energize RFID," RFID Journal, Oct. 18, 2002, at could enable active RFID to be used widely instead of passive RFID tags, but the present momentum for passive tags began before PowerPaper came on the scene. In future environments where low-cost active RFID tags can be used, locating and tracking objects can be done more readily with a limited number of readers. The active RFID tags of the future may even be at higher frequency ranges than presently used, which would offer several advantages. According to Tim Schröder in "Transforming Production with Tiny Transponders," Siemens Webzine, Oct. 31, 2002, at, scientists at Siemens AG in Münich are developing RFID tags that transmit in the high gigahertz range (from about 2.5 to 24 GHz). Tags already developed in the Siemens lab are reported to have very high ranges. According to the article:

Energy demand is also a key issue. Here, the lab has developed ultra-low power electronics that enable transponders to transmit across long distances. The extra-high frequency transponders from [Dr. Wolf-Eckhart] Bulst's lab are battery-operated and have an enormously long range--some can actually transmit over several kilometers. What's more, it is now possible for the first time to measure the distance between reader and transponder to an accuracy of 1 cm. This makes it possible to precisely locate a given transponder by processing run-time data from several readers, which opens the door to entirely new fields of application. "Our transponders can bring order to even the most chaotic materials flow because many objects can be localized simultaneously," explains Bulst....

Bulst adds, "There's one advantage that makes extra-high frequency technology especially interesting. These transponders can be tracked even where GPS fails, inside buildings and in the canyons between tall buildings. And it can all be done with a very modest investment in technology."

Another alternative to smart shelves with fixed low-range readers is to use long-range readers with directional antennas that sweep selected areas of a store to identify objects based on their RFID code. For such systems, highly sensitive electronics can be used to resolve faint signals at larger distances. By using advanced antennas in particular, RFID tags may, in some cases, be read from larger distances than previously recognized. The US military, for example, has developed sensitive electronics to extend the read range of passive RFID tags to large distances, as described in the article, "RFID Sensors: From Battlefield Intelligence To Consumer Protection," RFID Journal, Aug. 12, 2002, at Such ultra-sensitive radio frequency receivers rely on filtering systems to separate the RFID signal from background noise.

One antenna technology that may be useful in amplifying weak signals and determining the direction of a radio signal source is smart antenna technology, such as adaptive antenna arrays including a plurality of antennas cooperatively associated with processors that continually readjust the radio signals from each of the antennas to create radio systems with extremely precise directionality and the ability to greatly amplify detected signals. Basic information about such smart antenna systems is provided by Martin Cooper in "Antennas Get Smart," Scientific American, Vol. 289, No. 1, July 2003, pp. 49-55. Further information is given by Martin Cooper and Marc Goulburg, "Intelligent Antennas: Spatial Division Multiple Access," 1996 Annual Review of Communications, pp. 999-1002 (; in Joseph C. Liberti and T.S. Rappapport, Smart Antennas for Wireless Communications: IS-95 and Third Generation CDMA Applications, New York: Prentice Hall, 1999; and in various papers available at By way of example, manufacturers of adaptive antenna arrays include ArrayComm (San Jose, California) and Lucent Technologies (Murray Hill, New Jersey). Other antenna arrays can also be used, such as switched-beam arrays. Other beam-forming and beam steering technologies can be applied as well, such as the directional steerable antenna systems of Antenova Ltd. (Cambridge, England, see

Reading a tag from a large distance is typically not enough to locate the tag. However, if the tag can be read by multiple readers (e.g., two or more) at different locations, then triangulation can be done based on the arrival time of the signal to determine where the RFID tag is located. Alternatively, scanning by a single RFID reader can at least approximately determine the location of an object if the RF signal emitted by the reader is directional. Signals in the UHF range, such as a 2.45 GHz, tend to be highly directional (e.g., a narrow cone), and this effect has been used to locate individual cars in parking lots based on RFID tags on the automobiles. Other technologies can be employed to limit the scope of radio signals at other frequencies. In any case, a directional signal alone can identify the direction in which an object lies, which may not always be enough to successfully locate a given object unless at least one other directional RFID reader in another location is available to help identify the position by triangulation.

A single directional RFID reader can be used to more specifically locate an object along its beam path by varying the intensity of the signal to modify the range. When the response signal from the RFID tag in question drops out as the power of the RF signal drops, the estimated range of the signal can be used to help determine the distance to the object. To help calibrate the read range of a beam, beacons including a variety of known RFID tags may be installed at predetermined locations throughout the store. When a beacon's RFID tags drop in or out of range as the RF signal is varied, the read range can be estimated as the known distance from the scanner to the particular beacon being identified.

In some situations, GPS-type modules may also be associated with shelves, products, RFID scanners, or moving items such as shopping carts, humans, or automated guided vehicles (AGVs). Information on GPS systems is provided by Jon Titus in "Exploring GPS," Design News, Sept. 22, 2003, pp. 58-64. Manufacturers of GPS systems include CSI Wireless of Alberta, Canada (see, Garmin International of Kansas City, Kansas (see and Motorola TCG of Tempe, Arizona (see, which produces, for example, the FS OncoreTM GPS modules, measuring about 12 mm by 16.6 mm, small enough to be associated with individual pallets or portable RFID scanners, including RFID scanners built into cell phone units.

Other positional sensors can also be cooperatively associated with an RFID system. For example, magnetic positional sensors from Honeywell (Morristown, New Jersey), described at, can be used, including Honeywell miniature electronic compasses and other devices using anisotropic magnetoresistive thin film technology.

Any of these systems, as well as others proposed elsewhere in this paper, can be implemented using procedures, software, and hardware known to those skilled in the art. For example, object tracking and management systems for warehouses and other environments can be adapted for use in retail environments using the alternatives to smart shelves discussed herein. By way of illustration, one useful RFID-based system for tracking and retrieving objects in a warehouse or elsewhere is discussed in US Pat. No. 6,600,418, issued July 29, 2003 to R.C. Francis et al., entitled "Object Tracking and Management System and Method Using Radio-Frequency Identification Tags." US Pat. No. 5,689,238 to Cannon discusses an object location system and method using an electronic tag attached to an object containing a unique response code. Another useful reference is that of US Pat. No. 6,354,493, "System and Method for Finding a Specific RFID Tagged Article Located in a Plurality of RFID Tagged Articles," issued March 12, 2002 to J. Mon, assigned to Sensormatic Electronics Corporation. The abstract of the latter patent follows:

A method for operator feedback when utilizing an RFID reader to find a specific RFID tagged article located in a plurality of RFID tagged articles is provided. Specific search criteria associated with a desired article are entered into the RFID reader. To begin searching for the specific RFID tagged article, the RFID reader sends out an interrogation signal to the RFID tags. An RFID tag responds with the desired RFID tag data. A processor compares the number of RFID tags matching the search criteria to the total number of RFID tags received. A feedback signal is generated according to the ratio of RFID tags matching the search criteria to the total number of RFID tags received.
Such methods can be combined with the systems described in this paper for finding and retrieving specified objects.

Alternatives to Smart Shelves: Moving Readers

In some environments, RFID information is not needed continuously, and may only be needed for limited applications. In such cases, a small number of mobile RFID scanners may suffice for verifying inventory or for finding the location of sought-after objects. While handheld scanners could be used, it is preferred that automated systems employ mobile RFID scanners to track the location of objects. For example, one or more scanners could be mounted on overhead tracks or rails capable of traveling over shopping aisles to scan objects (rails may be single-direction rails or may be interconnected orthogonal systems capable of x-y traversing, such that one scanner may move to a position over any location on the floor of the store). In another example, RFID scanners could be attached to a fixed number of employees, shopping carts, restocking carts, janitorial carts, automated guided vehicles (AGVs) or other robots, and the like, such that the scanners pass through the aisles at possibly irregular intervals but with sufficient frequency to fulfill the limited objectives of the system. Scanners could also traverse aisles by being passed through a plastic tube through the aisle display itself (e.g., near ground level or immediately above the aisle) by a line, belt, or other means to pull or push the scanner.

In one embodiment, smart shopping carts are used that not only scan objects placed in the cart, but also provide a secondary function of scanning nearby shelves to verify the location of products. Smart shopping carts can be used from Toppan Printing (Tokyo, Japan--see Safeway, Inc. has also been testing and developing computer-assisted smart carts (see; also see Michael Liedtke, "Big Brother in the Cereal Aisle?," Associated Press, Dec. 18, 2002, available at Smart shopping cart technologies are also described by Jim Fitzgerald, "Smart Shopping Cart in Grocery Stores to Come," Associated Press, Sept. 30, 2003, available at and at

Any known motion control system can be used to assist in guiding the motion of one or more RFID scanners.

Antenna Systems for RFID Systems

The antenna system used by RFID readers can include any currently used for RFID applications and possibly many other designs as well, provided they are adapted for the frequency of the RFID system. For example, RFID systems in the UHF frequency range, such as 2.45 GHz, tend to be highly directional, making it relatively easy for a directional antenna to be used to identify RFID tags within a narrow cone. However, at lower frequency such as 13.56 MHz, conventional RFID readers tend to be less directional, though advanced antenna designs for improved directionality can be considered.

Numerous antenna configurations can be considered, including those discussed at such as square patches, the ¼-lambda spiral whip, the sub ½-lambda dipole, the ¼-lambda whip in spiral form, and the like. Antenova Ltd. (Cambridge, England), a spin-off of ActiveRF (Cambridge, England) also offers steerable directional antennas that may be of use with RFID systems.

In one embodiment, the antennas are small, such as less than 1-inch in length. Useful forms of small antennas are those associated with semiconductor devices, such as microstrip patch antennas. One form of microstrip patch antenna is described in the article, "Multimode Broad-Band Patch Antennas," NASA Tech Briefs, Vol. 27, No. 9, Sept. 2003, pp. 41-42, reporting on the work of Robert R. Romanofsky of the Glenn Research Center. Larger arrays of microstrip antennas can also be used (see "UHF Microstrip Antenna Array for Synthetic-Aperture Radar," NASA Tech Briefs, Vol. 27, No. 9, Sept. 2003, pp. 44, 46).

Any other antenna type may be considered, such as hollow-tube helix or flat patch antennas.

Antennas for the tags may be made by any method, including metal deposition, printing of conductive inks, etc. By way of example, the RFID tags may employ conductive ink technology of RCD Technologies (Bethlehem, PA) (see Antennae may be deposited or printed using any known format, and may, for example, include double-sided, interconnected coils. Any known frequency may be used, such as 100 kHz or 125 kHz ("low frequency"), 13.56 MHz ("high frequency"), 860-930 MHz such as 900 MHz or 915 MHz ("ultra high frequency" or UHF), and 2.45 GHz or 5.8 GHz (microwave frequency), or other known frequencies.

Antennas printed with conductive inks are an especially useful approach. One manufacturer of such systems in Flint Inks. (see the news item, "Flint Bets on Printed RFID Antennas," RFID Journal, Jan. 31, 2003, available online at A new business unit created by Flint Inks, Precisia, LLC (Ann Arbor, Michigan) produces conductive inks and printed electronics for RFID systems.

Carclo PLC (Wakefield, England) has announced development of new technology for printing RFID antennas with conductive inks, as reported in the news item, "New Way to Print Ink Antennas," RFID Journal, Oct. 20, 2003 (available online at, as viewed Oct. 31, 2003). According to this report:

Carclo developed a prototype printer that's about the size of a small photocopier. It can print copper antennas on polycarbonate, polyester, polyethylene and other plastic films used for RFID tags, as well as on paper and cardboard. The copper layer can be as thin as half a micron and is almost as conductive as a solid copper antenna. And unlike bulk metal antennas, the printed antenna is recyclable.

The new digital inkjet printer could reduce the cost of tags and make it economically viable to print antennas on packaging during the commercial printing process. That's because the process is fast--antennas can be printed at a rate of six feet per second--and it doesn't require any extra steps, such as curing in an oven. Boxes could have antennas printed on them and, after drying for 30 seconds, go straight to the next stage of production.

Another source of conductive inks useful in RFID antennas is Parelec of Rocky Hill, New Jersey. According to a Feb. 5, 2003 new item, "New Ink for Printed RFID Antennas," RFID Journal (available online at
Parelec Inc., a startup that makes conductive inks and pastes, says it has developed an ink that enables companies to print highly conductive RFID antennas on paper and polyester. Parmod VLT is commercially available and is being marketed as a way to produce low-cost RFID tags at high speed.

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.

Steve Ludmerer, president of Rocky Hill, NJ-based Parelec, says Parmod ink can help reduce the cost of RFID tags because the antenna can be printed and attached to the chip during the commercial printing process.

"We have demonstrated the ability to attach components to our printed circuitry in one operation," he says. "To do the same thing with RFID, we need the right metallurgy on the chip and some other developments, but the concept is clearly there."

A number of companies are working on developing techniques for printing RFID antennas using conductive inks. Flint Ink . . . recently announced it was investing millions in a new research facility for conductive inks. . . .

Ludmerer says Parmod VLT is different because instead of suspending silver and other metal particles in a polymer, Parmod uses an organic base that decomposes and leaves an antenna that is more than 99 percent metal. The company claims that because of this, its printed antennas are three to 10 times more conductive than polymer-based inks.

Greater conductivity means the tag can be read from further away than a tag with a polymer-based antenna. It also should reduce the cost of the antenna because less ink is needed to create an antenna with same performance level.

Other antenna systems can be adapted for improved RFID systems, including the active integrated antenna systems developed at the Technische Universität München by Prof. Peter Russer and others (see, for example, E.M. Biebl, "RF Systems Based on Active Integrated Antennas," AEU International Journal of Electronics and Communications, 57(3): 173-180 (2003). Low-noise amplifiers (LNAs), hollow-tube helix antennas, flat patch antennas, and the like may be used in the RFID reader, and, when needed, may also be associated with an active or passive RFID tag.

System Operation

In practice, the use of a non-smart-shelf object tracking system might begin with a request to find a particular object. A customer may request an item that is to be sought in a retail environment. For example, the customer may download an electronic shopping list identifying items to find. An in-store computer system may then determine which objects have known location and which have uncertain locations. The location of the uncertain items can then be tracked. A group of readers with long-range antennas may then scan a targeted region to find a passive return signal (or active signal or active assist signal) carrying an ID code for the targeted object. Once the presence of the object is confirmed, its location can be determined by triangulation or other means.

In another embodiment, scanning is done continuously by moving RFID scanners such as scanners in shopping carts or guided vehicles, and these are repeatedly scanning objects and allowing their locations to be recorded. Locating the object can then be as simple as retrieving the database record for its lasted canned location and going there. In other cases, more advanced triangulation may be needed to locate the object, including the use of variable strength signals and RFID beacons.

These principles can be extended to warehouse management, team management, and other business concepts. They can also be applied to inventories of any kind of object, either in a commercial or private setting. These systems can be integrated with other known retail technologies, such as vision-based systems for recognizing objects (e.g., IBM's "Veggie Vision" system--see


A variety of alternatives to the smart shelf can be used in retail environments and other settings to determine the location of an RFID-tagged article. The alternatives can include techniques for extending RFID signal range, use of active RFID tags with an inherently greater range, a limited number of moving RFID readers that scan RFID tags, and the like.

Appendix: RFID Basics

Basic principles of RFID technology are given by Raghu Das, "RFID Explained: An Introduction to RFID and Tagging Technologies," white paper from IDTechEx Ltd. available at, dated 2003, as viewed Aug. 19, 2003. The author defines RFID as follows:

Radio Frequency Identification (RFID) is the use of radio frequencies to read information on a small device known as a tag.... Radio frequency Identification (RFID) is a term used for any device that can be sensed at a distance by radio frequencies with few problems of obstruction or misorientation. The origins of the term lie in the invention of tags that reflect or retransmit a radio-frequency signal. In its current usage, those working below 300Hz and those working above 300MHz, such as microwave (GHz) tags, are included. For example, one type of chipless tag works at only a few hertz and Inkode chipless taggants operate at around 20-25 GHz. Higher frequencies such as visible and infrared devices are excluded as these systems have very different properties and are frequently sensitive to obscuration, heat, light and orientation.

The term "tag" is used to describe any small device -- shapes vary from pendants to beads, nails, labels or microwires and fibres that can be incorporated into paper and even special printed inks on, for example, paper.

RFID chips can be used to track products grouped in various hierarchies: (1) individual items or single packages containing multiple items for consumer purchase; (2) cartons or cases of multiple items; (3) pallets of multiple cartons or cases; and (4) loads (e.g., truckloads, shiploads, or railcar loads) of multiple pallets. The products at each of these levels may be assigned an RFID label that is associated with information pertaining to at least one adjacent hierarchical level. For example, an RFID label on a pallet may be associated in a database with the RFID labels for each carton on the pallet, or may be associated with data pertaining to the RFID label from the truckload.

RFID tags of any known type may be used, including:

While RFID tags typically include a semiconductor chip associated with an electronic code, chipless RFID technologies are also known.

Examples of low-cost technologies for producing chip-based RFID systems listed by Raghu Das (2003) include:

For chipless RFID, Das lists the following as available low-cost RFID technologies: Transistor-based chipless circuits can include laminar transistor circuits, including polymer film circuits such as those of Plastic Logic, Inc. or Philips Research Laboratories, thin film silicon, bioelectronics, etc. Magnetic wire and fiber systems for chipless RFID can include the products of MXT (Canada), HID (US), British Technology Group (UK), Fuji Electric (Japan), REMOSO Development (Netherlands), and Advanced Coding Systems (Israel). Laminar transistorless circuits can include diode circuits, printed electronics, EM tags of ACS, surface acoustic wave technology such as that of RF SAW, Inc., and LC arrays (swept RF) such as the devices of CWOSRFID (US) and Lintec (Japan), Miyake (Japan), Checkpoint (US), MIT Medialab (US), the rewritable chipless tag of Navitas (Japan). Thin magnetic films for chipless RFID can include conventional magnetics for non-contact reading, or the films of Flying Null (UK), 3M Intelligent Transportation Systems (US), Scipher TSSI (UK), etc. Magnetic assembly can also be used, such as the technologies of Scientific Generics (UK). The self-generation RFID technology of Siemens Roke Manor Research can also be employed.

A recent development in RFID is ultra wide band (UWB) RFID. As reported in the news item, "First Ultra Wide Band Tags Approved," Smart Labels Analyst, Issue 32, Sept. 2003, pp. 15-16, Parco Wireless (Portland, Maine) has been granted FCC approval for their UWB Precision Asset Location system that uses UWB pulses emitted by active tags to provide two- and three-dimensional location of objects to within a few inches. The system is presently being marketed for asset tracking in hospitals. Though the tags are much larger than standard RFID chips (roughly the size of a wristwatch, weighing over 40 grams each), they are said to provide several advantages, such as an indoor range of about 300 feet. Products and other objects equipped with UWB tags can also be used for the systems described in this paper.

In general, RFID chips may be read-only chips, which include a fixed electronic code, or they may be read-write chips, which allow new information to be added. The chips may also be associated with sensors to read sensor information and transmit a signal responsive to the information, such as a value from a biosensor. Exemplary smart labels including RFID technology associated with a sensor are the active labels of KSW Microtec (Dresden, Germany), including TempSens® active smart labels for measuring and recording temperature. KSW Microtec also offers smart labels produced by flip chip assembly methods.

RFID tags can take many physical formats, such as a microchip from 30 to 100 microns thick and from 0.1 to 1 mm across, joined to a minute metal antenna such as the Hitachi 2.45 GHz Mew chip, or they can be in the form of deposited alloys 0.5 to 5 microns thick on a 20 micron polyester ribbon 1 mm across as used in some banknote security ribbons. Another form is the "Coil-on-Chip" system from Maxell (Tokyo, Japan), which is a 2.5 mm square IC with a coil mounted directly on the chip. The chip is a read-write chip with 108 bytes of storage.

In addition, related devices such as the PENI tag of the University of Pittsburgh can also be considered for identifying objects wirelessly.

Exemplary RFID vendors include Matrics, Intermec, Alien Technology, Philips Semiconductor, and Texas Instruments. Manufacturing can be done by robotic techniques (e.g., "flip-chip"/"pick and place" techniques), fluidic self-assembly (FSA), the Philips "I-connect" method or the Philips "vibratory assembly" method, the Matrics PICA system (Parallel Integrated Chip Assembly, as described in the news item "New High-Speed RFID Tag Machine," RFID Journal, Sept. 19, 2003, available online for subscribers at or other known processes. (See also L. Frisk, J. Jarvinen, and R. Ristolainen, "Chip on Flex Attachment with Thermoplastic ACF for RFID Applications," Microelectronics Reliability, 42(9-11): 1559-1562 (Sept.-Nov. 2002)). Also of potential use for tracking and finding objects is the "mu-chip" of Hitachi with a built-in antenna on a sub-millimeter chip having a 128-bit serial number, as described by Jonathan Collins, "Hitachi Unveils Integrated RFID Tag," RFID Journal, Sept. 4, 2003, available at Exemplary RFID reader manufacturers include Intermec Technologies, Symbol Technologies, Matrics, AWID (e.g., their multi-protocol reader that can operate at various frequencies), and others. Software systems to support RFID systems are provided by IBM Global Services (which has acquired PriceWaterhouseCoopers), Texas Instruments, Manhattan Associates (particularly for integrated supply chain executions), SAP, and others. Printed RFID labels can be made using equipment from Zebra Technologies and other vendors.

Readers may also be integrated into or added onto a laptop, a PDA device, a cell phone, or other electronic device. Suitable readers may include the readers of AWID (see Jeffrey Jacobsen, op. cit.) or the RFID reader on a compact flash card marketed by Syscan International for reading 13.56 MHz ISO-compliant tags or for other frequencies, as described in the news item, "Get RFID Readers in a Flash (Card)," RFID Journal, April 22, 2003, available online for subscribers at

Chip-based RFID systems need not be limited to silicon chips, but can also include printed electronics, particularly polymer electronics (organic electronics) such as organic field effect transistors (OFETs), and other technologies. Principles of polymer electronics are given by J. M. Shaw and P. F. Seidler, "Organic Electronics: Introduction," IBM Journal of Research and Development, Vol. 45, No. 1, 2001 ( See also PCT publication WO 99/19883, published April 22, 1999 by S. Babinec et al. of Dow Chemical. A representative manufacturer of printed electronics technology is Precisia, LLC (Ann Arbor, Michigan), a business unit launched by Flint Ink (Ann Arbor, Michigan). Precisia, LLC produces printed electronics for RFID systems, including smart packaging, lighting, and displays. Conductive inks manufactured by Precisia, LLC including conductive particles of silver or carbon have been proposed for use in printed RFID antennas. Such inks can be applied by screen printing, flexographic printing, lithographic printing, gravure printing, ink-jet printing, and the like. Plastic Logic (Cambridge, England) is another firm producing printable electronics suitable for RFID applications.

Other components associated with RFID systems can also include polymer electronics or printed electronics. For example, display graphics can include organics LEDs (OLEDs), printed electroluminescent displays, printed organics application specific integrated circuits (organic ASICs), polymer thin film transistors (pTFTs), the light-emitting polymers (LEPs) of Dow Corporation (see and Appl. Phys. Letters, Vol. 77, 2000, p. 406), and the like.

Power sources may include printed batteries, such as those produced by PowerPaper (Einat Israel) or Cymbet Corp. (Elk River, Minnesota--see or may rely on energy harvesting techniques that convert RF energy into useful electrical energy.

RFID tags can be assembled using flip chip technology, in which chips from an RFID wafer are inverted and placed in contact with an antenna. Exemplary processes include the Matrics PICA process for chip attachment to the antenna.

The RFID system may follow the systems proposed by the MIT Auto-ID Center, including the use of an electronic product code (EPC); a Savant system to manage the codes being read with a distributed architecture and processes such as data smoothing, reader coordination, data forwarding, data storage, and task management; and Object Name Service (ONS) for matching EPC information to item information, typically using a Domain Name Service (DNS) to route computers to Internet sites; and Physical Markup Language (PML) to describe information about a product.

Other vendors of integrated RFID systems or other tools for RFID include CheckPoint Systems, Tyco Sensormatic, Escort Memory Systems, Psion Teklogix (particularly for software systems to assist in logistics), SAMSys Technologies, Savi Technology, SCS Corporation, TAGSYS, ThingMagic LLC, and others. Supply-chain software can be provided by Crimson Software, Descartes Systems, EXE Technologies, Globe Ranger, Manhattan Associates, IBM Global Services, SAP, and others. RFID readers include those of Alien Technology, Matrics, Intermec, iPico, and AWID (Applied Wireless Identification Group, Hollister, California).

For a given retail supply chain, the RFID system can operate for all products that have an RFID tag. The tag may be provided by the manufacturer, the retailer, or others, and may be embedded in the product, attached to the surface of the product by a label or adhesive means, or be otherwise physically associated with the product. The RFID tag may have a unique electronic product code or other code, or optionally may include more extensive information. As the product is received by a retailer, the product may be scanned and its code or other information from the chip can be obtained. Logged information about manufacturing, shipments, etc., may also be accessed from a database using the electronic product code as a pointer, or may be otherwise associated with the RFID tag, and this information may be screened or downloaded from a database by the retailer. As the retail product is received and stocked or shelved by the retailer, its location may also be recorded in a database, where such information can be associated with the electronic product code or with an entry for the product.

RFID-enabled products can be integrated into supply chain systems using any known tools. One exemplary software tool is Auto-ID Infrastructure (AII) marketed by SAP AG (Walldorf, Germany) for integration with SAP and non-SAP software systems, as described in the news article, "SAP Takes RFID into the Enterprise" by Bob Violino, RFID Journal, Oct. 13, 2003 (available online at, as viewed Oct. 31, 2003). According to Violino:

A key function of the infrastructure will be managing the massive amounts of data that will be generated by item-level tagging. But SAP says its Auto-ID Infrastructure will have other important functions. It will capture, filter and publish data--including product location, shelf life, price and inventory level--from many readers. It will aggregate and store information about shipping containers, pallets, cases and items. And it will receive and maintain data specifying the location and physical relationships between items, such as a particular item's location within a particular container.

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