Can UHF Tags Be Read in Both the Near and Far Fields?

By RFID Journal

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Ask The ExpertsCan UHF Tags Be Read in Both the Near and Far Fields?
RFID Journal Staff asked 5 years ago

I am looking to buy an RFID scanner, an antenna and passive tags that can be read from a maximum of about 10 feet away and a minimum of a few inches. What would you recommend? Do I need ultrahigh-frequency tags?

—Nicholas

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Nicholas,

All passive UHF RFID tags can be read in both the near and far fields, so they can be read from a distance of 10 feet or more, as well as from only a few inches away. However, most passive UHF readers have trouble reading a tag within a few inches of the antenna. I know that vendors have talked about tag designs that would enable a UHF tag to be interrogated from a distance and then with a near-field antenna from a few inches away, but I have not seen any such tags on the market.

Impinj’s Monza 4QT chip offers full- and short-range modes, but I am unsure how short the latter mode is.

There are several tags on the market that operate using either UHF or high-frequency (HF) RFID, enabling short- and long-range operation. Bristol ID offers such a tag (see Bristol ID Announces Dual-Frequency and Asset-Tracking Tags), and EM Microelectornic introduced a chip last year that offers both Near Field Communication (NFC) and UHF functionality (see Inlay Companies Testing EM Micro’s Dual NFC and EPC Chip). To read both passive UHF and HF tags, you would need either two separate readers or one designed to interrogate both frequencies.

—Mark Roberti, Founder and Editor, RFID Journal

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