Progress with Next Generation RFID Technology
2006年11月15日 Dr Peter Harrop
RFID technology is moving on apace in some areas. Certainly EPC Gen2 tags have demonstrated spectacular performance improvements when tagging cases and pallets. However work is still needed.
Meeting the promises made for UHF
The original promise for passive UHF tags was that their longer range, under North American radio regulations at least, would translate into reading cases in a pallet load even if they are out of sight and regardless of their content or environment. We are still not there on that one. However, this year, Tyco ADT reported routine reading of all hidden cases in a load provided the contents are not too challenging to UHF. Accu-Sort has kept air baggage well separated at Oslo Gardermoen International Airport in order to get good reads to the IATA UHF specifications as have others at other airports, a UHF shielding shroud for one bag at a time being commonly employed by Symbol Technologies. However, San Francisco International Airport reports that it gets excellent reads at UHF on baggage by employing the new readers with focused beams from Quatrotec, a subsidiary of Alien Technology. Meanwhile, operational improvements have come along to reduce the problems such as reader to reader interference in regions with tough UHF regulations such as Europe.
So far, the uses of UHF RFID employ the Far Field to get range of at least one meter and usually several meters. Many different antenna shapes are employed depending on location so newcomers must learn the taxonomy of the flag, Excalibur, swastika, maxi squiggle, cross, frog, banjo, propeller, wave and many more weird and wonderful shapes, one of which, from Avery Dennison, is claimed to be tolerant of many types of content in a case. However, no supplier is near to offering one tag for everything, or even four. This can scarcely be considered a mature technology when there is no agreement on the best antenna even for a precisely defined location and environment but at least that means that further improvements can be made.
Item level - redrawing the battle lines
To compete with the world's most popular RFID frequency - HF - which is even favored by many drug companies for item level tagging, this year, the UHF proponents have stopped recommending Far Field UHF for item level tagging. Item level tagging is potentially the biggest RFID market of all. This year it was number three in value after cards then animal tagging and way ahead of pallet and case tagging in value, so there is a lot at stake here.
The new position of UHF proponents is to recommend Near Field UHF for item level tagging. This has never been executed in the millions but there is every reason to believe that the tag antenna will be cheaper this way because it involves one turn instead of seven in the HF version, those seven turns having to be high conductivity and of precise shape in a tuned circuit. There is every reason that, within its adequate range of 70 centimeters, Near Field UHF will be just as tolerant of water and metal as HF because both will work by inductive coupling. Further, the antenna design will be the same for almost all applications as it is with HF today.
Gradual adoption of Near Field UHF?
Progress will be gradual on Near Field because UHF readers can be more expensive than HF ones as yet and it is not yet clear what the profitable ie enduring price of a UHF chip will be, or the price of equivalent HF chips to an equivalent specification in billions. Then there is the fact that HF is a global RFID frequency whereas UHF will never be approved globally to the same frequency, power level, or bandwidth. Even the permitted signaling protocols differ around the world as yet and this impacts both performance and standardization for cost reduction. Indeed, the Near Field Communication NFC RFID enabled mobile phones that are so popular in Japan, and soon the World, will only sense HF tags. Progress is being made: that is all we can say.
We should also describe progress with HF tagging as incremental but significant nonetheless, whether it is the printing of antennas directly onto label feedstock at Hyan Label in China or the delivered achievement of HF ranges of several meters in many projects by DAG System, UPM Raflatac and others. These HF systems can easily read hidden cases on a load but the long range HF tags are expensive and the use of UHF is now a de facto standard for this application in the West at least.
Learn more in the IDTechEx report Near Field UHF RFID vs HF for Item Level Tagging.
Active RFID is now 20% of the RFID market by value and gaining share. With active RFID, we need sharp cost reduction of semi-passive time temperature and other RFID labels and cards with sensors. A breakthrough occurred with parasitic WiFi being used in volume as Real Time Locating Systems. A new chip has sharply eased the problems of power (very short battery life) and cost of the tag with WiFi tags but there is more to do because some of these systems only work 70% of the time and accuracy is sometimes poor. Disposable RTLS tags would have a huge market but none are yet in sight. Meanwhile, Wavetrend active RFID systems are now routinely monitoring assets at several kilometers and WhereNet high integrity RTLS systems now have the option of small tags suitable for typical indoor uses on assets.
Surface Acoustic Wave SAW tags have gained serious orders for logistics and military use in the USA this year. With no threshold voltage they can sometimes beat the range of passive chip tags and they can work at a wider range of temperatures. However, no one is yet offering them at low cost on the back of their simpler construction. Printed transistor circuits for RFID remain one year away and they will have to be made on inserts for some years, not directly applied. In parallel, ACREO, M-real and Somark Innovations continue to trial their ink strip RFID printed directly onto things. This approach gives 0.1 cents fitted, so there is no cost problem even for the highest volumes. Some no longer need the reader or tag to move for a read to be registered but none can give read write, multi-tag reading, active or sensor tags and the footprint is large when considered for small items like drug bottles, a problem also suffered by the transistor circuits. Printed ink stripes, whether of polyanilene or PEDOT, work at non-standard frequencies.
It is interesting that ACREO has just spun off its dry phase patterning process as a startup business. That uses metals and may be useful for several forms of next generation, directly applied RFID as well as antennas for some of today's tags.