Aug 29, 2012The latest annual report on ultrahigh-frequency (UHF) tag performance published by the European EPC Competence Center (EECC)—known as the UHF Tag Performance Survey (UTPS) 2012/2013—finds that radio frequency identification tags are becoming considerably more effective in high-proximity reading scenarios (in which multiple tagged items are packed closely together), and have also become highly sensitive to forward RF transmissions (from a reader to a tag). When these sensitive tags are interrogated from a long distance, however, the backward, or backscatter, transmission range (from the tag back to the reader) is decreased, and thus may require more sensitive fixed readers. Currently, according to the EECC, there are no handheld devices that can consistently read such tags when they are located at the far end of their interrogation range.
The results, the EECC reports, indicate that tag manufacturers have been quick to address perceived shortcomings in passive EPC UHF tags, by increasing tags' read effectiveness when in close proximity to many other tags, or when far away from an interrogator. Reader sensitivity issues, on the other hand, may be the next challenge for RFID hardware manufacturers, to ensure that these more sensitive UHF tags can be read, when in either distant or high-proximity scenarios, such as those found when tagged items, such as DVDs, textiles or books, are tightly packed in boxes.
EECC has been publishing some of the most comprehensive tag benchmark reports since it began conducting studies in 2007 (see European EPC Competence Center Releases UHF Tag Study). For this year's report, the organization included a greater number of tag models and tag suppliers than ever before—191 altogether (86 of which were on-metal tags), from a total of 25 manufacturers, versus 118 tags in total in 2011 (see RFID News Roundup: EECC Delivers Updated Study on UHF Tag Performance). This was the result of a greater number of tags being produced by the Asian market. "There are new suppliers with good tags," says Conrad von Bonin, EECC's general manager. What's more, he adds, companies are producing more specialty tags, such as those designed for tracking laundry. The first study included 20 passive UHF tag models from six manufacturers.
The EECC was founded in 2005 by GS1 Germany and German retailer Metro Group, with a goal of supporting the implementation of EPCglobal's standards for RFID. Its reports are aimed at systems integrators and RFID solutions providers, rather than end users, and its plan is to develop reference materials indicating which type of tag is best suited for a particular application, as well as which reader may be most effective with that tag. Ten EECC researchers spent approximately five months studying the tags during tests performed in the center's lab in Neuss, Germany, focusing on technical limitations and methods for overcoming them. The team simulated testing that adhered to U.S., E.U. and Japanese regulations specified by, respectively, the Federal Communications Commission (FCC), the European Telecommunications Standards Institute (ETSI) and the Association of Radio Industries Businesses (ARIB).
Throughout the past two years, the study has included a Proximity Stability Indicator (PSI) to test RFID tag reads in bulk. During the study, a stack of 11 tags are placed 1 centimeter (0.4 inch) apart, so the 10-centimeter (3.9-inch) stack is read in order to determine the read range not only of the tags on the outside of the stack, but also those inside, where density can reduce read range. The ranges decrease by 40 percent or more for transponders packed densely with other tags, the study reports; past tests have found that tag orientation could affect read range.
Proximity testing conducted in 2011 found that only a single tag could be read within a highly dense environment (such as in a load of tagged CDs or garments), with the tag and reader situated 4 meters (13.1 feet) apart. This year, however, a total of seven tags from six manufacturers using three different types of RFID chips were able to be read at that distance within a dense environment. "That is really enormous," von Bonin states. The six vendors offering tags that reached 4 meters in read range were Alien Technology, Avery Dennison, Checkpoint Systems, Invengo, Smartrac and Trace-Tech ID Solutions. Each tag was tested in a horizontal position, in order to replicate its orientation in a typical real-world deployment, such as attached to CDs stacked on a store shelf.
The tags that performed well had a variety of form factors and used chips supplied by Alien Technology, NXP Semiconductors and Impinj, von Bonin says. He adds that the results show there was not one specific new design or chip that increased read performance.
When it comes to providing greater tag sensitivity, von Bonin says, "All tags in the new generation seem to be moving in this direction." Tags may become activated by a reader located 10 meters (32.8 feet) or more away, but an interrogator may not be able to pick up the tag's lower-energy backscatter signal.
These more sensitive tags, EECC reports, require readers of greater radiating power, or decibels per milliwatt (dBm). Readers operating at -70 dBm or -75 dBm operate well with the more sensitive new tags. To put those numbers in perspective, most handheld readers operate at -50 dBm.
Von Bonin speculates that companies manufacturing handheld readers, as well as systems integrators that install fixed interrogators, may begin working on a solution, with antenna arrays and readers that can better capture low-energy transmissions. Much of this, he says, may involve improving reader antennas. "I think the next wave (of technology improvements) will come out of the antenna market," he states.
The full UTPS 2012/2013 report is available at EECC's Web site, at a cost of €995 ($1,246) for a one-time purchase, or €495 ($620) as part of a five-year subscription.
