It is usually taught that RFID at more than one meter range is impossible under the radio regulations of most countries other than at UHF, a band of license free frequencies around 900MHz. True, longer range has always been available if there is a battery in the RFID tag, and this is a viable solution for vehicles and trailers. However, these so-called active tags have limited life and they are expensive, relatively large and with more parts to go wrong. That has meant that UHF passive tags have been standardized for pallets and cases of food and other produce at the behest of leading US and European retailers and the US Military.
UHF RFID not ideal for all food applications
However, although UHF RFID works reasonably well with nothing in the way, indeed it is starting to be adopted for ear tagging of cows as well, it can behave very unpredictably when water or metal is nearby, let alone in the way. As Hong Kong Airport (tagging baggage) and Metro (trialling tagging of food) have found, sometimes the proximity of water or metal can prevent any reads taking place. At other times, things can be unexpectedly and annoyingly sensed 50 meters away, creating confusion about what one is sensing. In Europe, the problems of UHF are compounded by the Military and other vested interests preventing UHF radio regulations permitting higher power and wider bandwidth and this is greatly restricting range and control of interference between readers in trials of pallet and case tagging of food. Improvements to UHF systems are coming along but there is also help in prospect from great advances recently in the traditional HF (13.56MHz) and microwave (2.45GHz) systems making them longer range and more suitable for traceability applications.
These advances include
- Password protected HF tags of controllable range, more tolerant of water and metal than those at UHF. The major retailers demand password protected read write tags and these had only been available at UHF where EPC standards are involved.
- New ways of extending the range of HF RFID, sometimes even to ten meters.
- Use of Surface Acoustic Wave chips to replace the silicon chips in RFID tags. These have no threshold voltage, they can sense temperature without additional sensors and they are inherently simpler to make.
Password protected HF tags
As one example, Texas Instruments has just released a password-protected, standards-compliant write mechanism for HF tag data; introduced a rigorous quality control inlay-manufacturing process; and offered a unique solution for pharmaceutical tagging that will be relevant to food.
This helps to tackle another aspect of the pharma supply chain: privacy. In stark contrast to the retail and CPG space, pharma industry players have reached a consensus that drug tags should not be deactivated ("killed") upon purchase by the consumer. Indeed, Nestle and other food companies have said that killability is neither viable nor necessary. One of the key potential benefits of drug-tagging is vastly improved recall processes, which would require returned drug bottles to have retained identification information on their tags. The problem, of course, is that not killing a tag leaves the consumer vulnerable to privacy invasion. Drug prescriptions can be highly sensitive personal information, and consumers would be loathe to accept the possibility of a hacker "skimming" the names of drugs located in their shopping bags as they leave the pharmacy.
The password-protection write functionality offers a solution. The drug's product information and serial number are stored on the tag throughout all points in the supply chain, until the bottle reaches the pharmacy. At the pharmacy, the product information is completely erased while the serial number remains untouched. Thereafter, even if a hacker succeeds in reading the tag, no identifying production information exists, only a serial number that offers no indication about what the drug actually is. Furthermore, in the event of a recall, the consumer could return the tagged bottle to the pharmacy, where the serial number would be entered into the system and reassociated with its product information to determine if it is in fact part of the recall. Eventually, item level tagging of food in the supermarket will have to involve tags staying on after the till and not being deactivated. IDTechEx finds that 30% of the potential benefits and paybacks at item level occur after the till including better recalls, fraud reduction and consumer rewards.
Longer range RFID at HF
Icelandic Fisheries successfully trialled HF for wet fish in pallets and cases because UHF did not work but range was only one meter with the usual credit card sized HF label. More would have been welcome. There are even those who argue that the total cost of ownership can be lower with an HF system working at, say two meters. For example, there are no large royalties to pay - contrary to the situation at UHF - and ten times as many HF tags have been made, giving economies of scale. (However, the volume story is changing fast in favour of UHF).
Many ways of achieving longer range at HF
There are many new ways of achieving longer range at HF without necessarily having very large tags and readers. At Metro, one of the world's largest supermarket chains, they want to tag at item level using one frequency and one standard system if possible. For short range smart shelving, HF seems best because at short range it gives the smallest tag, it is controllable (you know exactly what range you are achieving) and there is therefore no problem distinguishing one item from another. A UHF label may be looking at the wrong thing and the tag can be too big for small food items. For large items, the Metro approach is not to make the HF tag enormous but to use large interrogatory antennas rather like the anti-theft tag pedestals in stores. Maruetsu in Japan has had a similar approach with their many trails in their food stores at HF.
The large tag option
Others go for large HF tags and more modest interrogators. For example, in recent trials, the DHL postal tag covers the whole of the package. Supplied by Denstron, it was so successful in trials that an invitation to tender for one billion has been issued, dwarfing UHF pallet/ case orders to date. It will meet EPC/ ISO standards. (Another myth is that you cannot have ISO tags at HF - ASK and others happily offer them). Large HF labels for two meters range are not a new idea. For example, UPM Rafsec of Finland has long sold them at around A5 size to go on the back of the number on the chest of the marathon runner. Miyake of Japan has fitted large numbers of roughly A5 size labels on pipes that see through two meters of soil using frequencies around 13.56 MHz. These use no chip and are a "Swept RF" LC array but the large laminar coil antenna is the same.
Smaller HF tags for long range
However, these "large antenna" solutions are greedy of production capacity which is area limited in reel to reel processes. Any other approach is also therefore interesting. For example, a French company DAG System, the electronic branch of the PYGMALYON company, has been developing and manufacturing RFID systems since 1998. Holding several patents, PYGMALYON has developed a unique technology of "unconstrained" detection in the band 13.56 Mhz for which they claim long distance detection of up to 10 meters through large area or volume (2D or 3D) unlike UHF which usually approximates to a beam, often with blind spots. With antennas able to detect tags within a 60 cubic meter volume, this technology was first developed and sold for sports events. For example it was used in the Rome Marathon. The current DAG tag for many meters range is rather large but other companies have developed so-called fractal antennas to reduce the size of such tags for a given range. Energy harvesting can also be used to keep tag size small. None of these tags have any problem with the water associated with most foodstuffs.
Breakthroughs in SAW RFID
Surface acoustic wave SAW RFID has been around for some time, benefiting from reliability and cost reduction that comes from the billions of non-RFID SAW applications in mobile phones, pagers and so on. SAW RFID first appeared in non-stop road tolling in California and Norway but numbers were small and, in California, they were replaced by silicon chip based RFID tags in the car windshield. In Norway, MicroDesign continued for over a decade supplying read only passive versions. Since then it has traded as QFree selling silicon chip based active read write devices and systems for non-stop road tolling and other equipment. Indeed, to this day, no one knows how to make SAW RFID that is active or read write, though RFSAW of Dallas has done some excellent work showing how it can sense strain or temperature without extra sensors and even give position. Both functions are possible with silicon chips and separate sensors but only at considerable cost. For example, cattle and food have temperature monitoring RFID today but only in limited numbers.
Potentially lowest cost at highest volume?
However, although a disadvantage with SAW RFID is that it still employs a brittle chip like silicon, at least the processing steps are fewer and less precise, giving the promise - not yet realised in the marketplace - of lower cost than silicon chip based RFID. RFSAW has established sales of SAW RFID devices into many industries, it has also been prime mover in creating a subset of ISO 18000 to cover such devices.
- reliable reading at large separation between tag and reader
- surmounting the tendency of liquids and metals to block reading signals, and
- commercial full pallet reading which is a vitally important RFID capability.
In many applications, SAW tag read range is sufficiently large so that passive tags can replace high-cost battery-powered active tags. SAW-based RFID systems have the inherent ability to measure tag position, direction of travel, and tag temperature, which are costly or difficult to implement with competing technologies. Furthermore, SAW tags can withstand security and safety related processes that involve elevated operating temperatures, high energy x-rays, or gamma ray sterilization as is used with some food and medical supplies.
As an example, the RFSAW Global SAW tag uses an inherently lower cost chip in combination with a smaller, less costly tag antenna, which results in a cost advantage over competing IC-based tags. In addition, overall system cost is optimized by placing key signal processing functions such as multi-tag reading in the reader unit instead of the tag. It is enabled by multiple-access spread-spectrum signaling that provides the necessary high-speed reading with substantially higher interference resistance and spectrum compatibility with other radio frequency systems and RFID readers. Unlike UHF, it can operate legally worldwide today - no need to await European, Chinese and other radio regulation reviews. 256 bit versions are possible - far more than the memory demanded for item level, pallet and case tagging, let alone other conveyances and vehicles.
Other companies develop SAW RFID
These activities have led giant Samsung of Korea to announce that it had a program to develop SAW chipless RFID, apparently to get costs down against silicon chip RFID which is going to be about 12 cents per tag in highest volume in 2006 to EPC Gen2, quite unacceptable for most item level tagging. Thoronics of Germany has created a SAW design house for custom design of SAW RFID tags. Carinthian Tech Research (CTR) of Austria, has recently developed new passive RFID tags able to tolerate and monitor temperatures in engineering and industrial applications rather than the high volume low cost applications made possible by RFSAW.
Clearly the advances in RFID relevant to food and livestock traceability are coming thick and fast. The major conference Food Traceability, Dallas February 1-2 will see Abacus Biotech of new Zealand presenting on use of HF for cattle tagging, Hitachi giving new information of use of Microwave RFID for food and livestock tagging in East Asia and local company RFSAW present on SAW tags for food. There will be presentations from across the world on all aspects of RFID tagging of food and livestock, use of DNA, temperature dependent barcodes and other exciting new technologies for these purposes. Also located in Dallas are Texas Instruments and Maxim Dallas Semiconductors, which is shortly launching a time temperature recording RFID label for food. IDTechEx can make appropriate introductions so a visit to the Dallas area can be particularly fruitful. For more information, see www.trackingfood.com