University of Kansas Lab Develops Foam-Attached Tag

By Beth Bacheldor

June 24, 2008—The Information & Telecommunication Technology Center (ITTC) at the University of Kansas (KU) has developed a new passive ultrahigh-frequency (UHF) tag technology known as Agility, designed to perform well when placed near metal or conductive liquids, which can often interfere with RF waves.

The technology follows ITTC's KU-Tag technology, announced in 2006 and also designed to work with metals and liquids (see University of Kansas' Tag for Metal, Liquids). Both the KU-Tag and Agility were developed by Dan Deavours, an ITTC research assistant professor and principal inventor. A KU-Tag inlay has a rigid solid core containing a rectangular microstrip (patch) antenna and a foil ground plate, with a plastic substrate separating the foil from the antenna in the middle.

Dan Deavours

The foil ground plate is a thin metal sheet that serves to isolate the antenna from any other metal or fluid that can lower a tag's read range. Because the antenna cannot make contact with the foil ground plate, the substrate must be thick enough to fully separate the two. A KU-Tag inlay's thin design differentiates it from other comparable tags on the market. On average, an RFID tag with a metal ground plate for isolating the antenna is approximately 5 millimeters (0.20 inch) thick—nearly four times thicker than a KU-Tag inlay, which measures about 1.5 millimeters (0.059 inch).

An Agility inlay, on the other hand, is a foam-attached tag (FAT), which Deavours describes as "simply an inlay, possibly converted to a label, with foam that has adhesive and a release liner on the back. That's it—no ground plane." The inlay has a 2/16-inch-thick foam layer, thinner than that of other FAT tags on the market, such as MetalCraft's, which measures 3/16 inch in thickness. (According to Deavours, ITTC is considering developing a FAT tag as thin as 1/16 inch.) The Agility inlay's antenna is designed so that when the tag is placed on metal, the antenna offers approximately the same read distance as it does in free space—typically, 15 to 20 feet.

"Unlike all other known FAT tags, our antenna design allows the antenna to work perfectly in free space and work extremely well when placed on metal," Deavours says. "There is conventional wisdom in the industry that tag performance degrades when the tag is near metal, and that's just the way it is—the laws of physics dictate it to be so. The big deal is that we demonstrate that conventional wisdom is wrong. We don't change the laws of physics; we're just clever in how we apply the laws of physics. This tag can be used like any other tag. It also happens to be a very good general-purpose tag, and it's a very good metal tag."