The following article on nested or cascading RFID tags was published Dec. 23, 2003 on IP.com as Article 21112D, available at https://priorart.ip.com/viewPub.jsp?pubID=IPCOM000021112D.
Related articles at JeffLindsay.com on radiofrequency identification (RFID) technology:
In pilot trials done by Gillette and Wal-Mart, several problems in implementing RFID technology have been encountered. In a warehouse or distribution center, some tags fail to be read by scanners due to shielding of radio signals resulting from radio frequency (RF) blocking materials (e.g., metal and liquids), interference between multiple tags, nodes in the distribution of emitted radio signals, distance between tags and scanners, and other factors. For example, in a pallet with multiple stacked cases of product, products in the center may not be read easily, while those on the outer portions of the pallet may be readily detected by scanners. Failure to scan and read all products in a case, on a pallet, in a truck, or in a warehouse can result in inefficiencies and loss. An improved system is needed to ensure that products are detected even when there is RF shielding or other problems that cause some tags in a group of products not to be read.
In general, 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.
A related concept to the cascading RFID system has been proposed by Savi Technology (Sunnyvale, California), which announced a collaborative effort with Matrics Technology to combine short- and long-range RFID tags for "nested visibility" in the supply chain, as reported in the news item, "Passive, Active RFID Tags Linked," RFID Journal, July 24, 2003, available at http://www.rfidjournal.com/article/articleprint/512/-1/1/, as viewed July 25, 2003. In the past, the article notes, Savi Technology's customer would write information scanned from bar codes on individual boxes and write the summary information to a read-write active tag (Savi's EchoPoint tag). By replacing the barcodes on boxes with passive RFID chips, the contents of a container or trailer having multiple boxes will be more visible, allowing the RFID tags to be scanned within the container or trailer for comparison to the written information on the active tag. This comparison can enable detection of missing items or point out possible tampering. Savi proposes replacing barcodes at both the carton and pallet level with passive tags.
The concept of nested or "cascading" RFID systems can be extended even further, or offered in other combinations. Here we propose a number of additional variations that might be of benefit to the supply chain and other applications.
By using tags with two or more technologies, it may be possible to read macro tags only--without interference from product tags--or to read tags at only one level of the hierarchy. Reading tags at a high level can be used to reliably extract information at lower levels, or to verify the accuracy of the information obtained from lower level scans. Again, the scans at different levels of the hierarchy may employ differing frequencies or signal strengths to simplify the scanning process and keep it targeted at the level of interest.
Further, the various levels of the system need not all employ RFID tags or rely exclusively on RFID tags for identification. Any one or more of the labels may, for example, use bar codes or other vision-based identification systems instead of or in addition to RFID technology.
In some cases, the cascading structure may not be truly nested. For example, one macro tag may describe the contents of two or more related shipments on two or more pallets that are not physically joined, while each pallet may further have macro tags describing the contents of the pallets, in a nested relationship with the cartons and products of the pallet.
The active/passive characteristic is not all that can be varied. Whether they are active or passive, the tags in the nested system can also vary in terms of other features, such as frequency, writeability, and range (e.g., antenna size). Thus, one or more levels of a nested system may operate at UHF frequencies (e.g., 920 MHz, 2.45 GHz, or 5.48 GHz), while other levels operate at, for example, 13.56 MHz, which would allow differentiation of levels by using different readers or coordinated systems within the same reader. Writeable tags could be used for one or more levels, if desired, or the entire system could be based on passive RFID tags.
In addition to considering a combination of active and passive tags, semi-active tags could be used at any level as well. For example, PowerPaper's Power ID semi-active tag system could be used for improved sensitivity to RFID reading.
For example, if an RFID tag on one level contains or is associated with all the information from the RFID tags at the next lower level, a scan of the higher-level tag can provide the same information as a scan of the previous level tags, and conducting both scans can be used to verify the accuracy of the scan, or possibly to identify missing or damaged items. Scanning of items at multiple levels, such as three or more, for comparison of redundant information can also be done as a check on the accuracy of scanning or as a means of identifying other problems.
www.idtechex.com, 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.Examples of potential applications for smart chips attached to products and wireless communication systems are described by C.R. Schoenberger in "The Internet of Things," Forbes, March 18, 2002, pp. 155-160. Further information on these technologies is provided at http://www.mccombs.utexas.edu/news/magazine/01f/alien.asp and http://www.mindfully.org/Food/The-Code.htm, and more technical information has been provided by MIT's Auto-ID Labs (formerly the Auto-ID Center), Cambridge, Mass. Useful information from the Auto-ID Labs can be accessed from www.autoidlabs.org/ and other information can be obtained at http://archive.epcglobalinc.org/aboutthetech.asp. See also "Toward the 5¢ Tag" by Sanjay Sarma, Auto-ID Center, Nov. 2001, available at http://www.autoidlabs.org/whitepapers/mit-autoid-wh-006.pdf, and "Integrating the Electronic Product Code (EPC) and the Global Trade Number (GTIN)," by David L. Brock, Auto-ID Center , Nov. 2001, available at http://www.autoidlabs.org/whitepapers/mit-autoid-wh-004.pdf.
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.
An overview of the history of RFID is given by Jeremy Landt in "Shrouds of Time: The History of RFID," AIM (Association for Automatic Identification and Data Capture Technologies), Pittsburgh, Pennsylvania, Oct. 1, 2001, available at http://www.aimglobal.org/technologies/rfid/resources/shrouds_of_time.pdf.
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:
Examples of low-cost technologies for producing chip-based RFID systems listed by Raghu Das (2003) include:
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.
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 http://www.rfidjournal.com/article/articleview/586/1/1/) 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 http://www.rfidjournal.com/article/articleview/556/1/1/. 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 http://www.rfidjournal.com/article/articleview/393/1/1/.
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 (http://www.research.ibm.com/journal/rd/451/shaw.html). 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 www.lumation.com 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 http://www.rfidjournal.com/article/view/94) 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 http://www.rfidjournal.com/article/articleprint/613/-1/6/, 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.
Finally, an alternative to typical low-range readers is to use long-range readers with directional antennas that sweep selected areas 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, available online at http://www.rfidjournal.com/article/view/182. Such ultra-sensitive radio frequency receivers rely on filtering systems to separate the RFID signal from background noise.
One antenna technology that may be particularly 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 (see www.arraycomm.com/Company/spatial_division.pdf); 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 www.arraycomm.com/Company/white_papers.html. 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 www.antenova.com/).