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Wal-Mart Seeks UHF for Item-Level
During a recent webinar, the retailer's RFID solutions architect explained his company's criteria for successful item-level tagging.
The approach is simple, they said: Without altering the Gen 2 chips or the air-interface protocol, manufacturers can use tag and interrogator antennas specifically tuned for near-field operation, which uses the magnetic energy field between the tag and reader antenna to communicate data, thereby shrinking the tag's read range and making the reader's interrogation zone more targeted.
Diorio said the near-field prototype tags and readers Impinj demonstrated last month performed as well as high-frequency tags when placed on items containing water or metal—notorious for causing RF interference with conventional UHF tags designed for far-field transmissions, or those using the electromagnetic energy field. In fact, he added, Impinj has demonstrated a number of its near-field UHF Gen 2 tags being read while submersed in liquid. This is because the near-field tags transmit through the magnetic field, and their transmissions are unaffected by dielectrics—materials that cannot conduct electricity—whereas the RF signals reflected by far-field UHF tags, which use the electromagnetic field, are attenuated by dielectrics.
Many end users, especially those in the pharmaceutical industry, are testing and using HF tags in pilots because they find that HF offers better performance than the UHF tags on the market today.
ODIN Technologies, a systems integrator based in Dulles, Va., released this week the results of a benchmarking test showing that HF tags outperformed UHF tags in both lab tests and use-case scenarios involving pharmaceutical products tagged at the item level (see Study Says HF Rules for Pharma Items). During the webinar, Diorio said the ODIN report was based on a foregone conclusion because ODIN used only commercially available tags and, therefore, compared HF tags with far-field UHF tags, which are not designed to work at close range. Diorio says tags using UHF Gen 2 chips and antennas designed for near-field RF communication—which he said are months away from being commercially available—are very well suited for the item-level tagging of pharmaceutical products.
In fact, said Diorio, near-field UHF tags have an advantage over HF tags when used in the supply chain, where goods need to be interrogated while in motion, because the higher frequency facilitates faster encoding and reading than HF tags do. Moreover, he said, UHF tag antennas can be built more cheaply and quickly than HF antennas since UHF tags can contain an antenna that is a less precisely designed and conductive.
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