Wal-Mart Seeks UHF for Item-Level

According to Diorio, Impinj has developed a tag antenna design called the Satellite, which has a small loop antenna in the center, linked to a larger antenna surrounding the loop. The Satellite is designed for both far- and near-field reading. When presented to a near-field reader antenna, it transmits in the magnetic field, and when presented to a far-field reader antenna, it functions like a far-field tag, using the electromagnetic field.

Forster says Avery Dennison has been working with Impinj to develop EPC Gen 2 inlays using near-field antennas. Exploiting a UHF tag's near-field capacity is nothing new, he explained—RFID printer-encoders such as those manufactured by Avery Dennison use near-field reader antennas to encode and verify the UHF tags embedded in smart labels. Avery Dennison also uses near-field reader antennas in its tag-testing machinery. According to Avery Dennison senior business development manager Andy Holman, two inlays in the company's recently expanded Gen 2 portfolio (see Avery Dennison Unveils New Gen 2 Inlays) use near-field antenna designs. Specifically, the AD-811 and AD-812 inlays for pharmaceutical applications contain an antenna designed solely for near-field transmissions, while the AD-820 and AD-821 inlays for apparel and other item-level applications contain an antenna designed for both near- and far-field.

If using UHF tags to track goods at the item level requires nothing more than new antenna designs, if none of the air-interface or chip specifications need to change, and if printer-encoders already use near-field to produce smart labels, then why is the concept of a near-field UHF tag for item-level tagging just now coming to the fore?

"Nobody was asking the questions," explained Diorio. "Everyone was too focused on case- and pallet-level tags. But the technology was there—it only took us about four weeks of experimentation to make our first prototype."