What frequency range would be best suited for an RFID system that needs to detect tags located between 6 inches and 5 feet away, while operating within a Faraday cage—an enclosure formed by conducting material, or by a mesh of such material, to block out external static and non-static electric fields—in a room measuring 10 feet by 10 feet by 8 feet? Should load modulation or backscatter detection be employed in such a scenario?
To achieve reads from five feet away, you would most likely need to utilize passive ultrahigh-frequency (UHF) tags, which use backscatter to communicate with readers. It is possible to extend the read range of high-frequency (HF) tags to five feet, but that would involve special reader antennas that are not really necessary. You could easily achieve 5 feet of read range via UHF.
Tags as close as six inches are sometimes a challenge to interrogate. I have been told that tag providers have designed tags able to operate both in the near field (within one wavelength of a reader) and the far field, but I am unaware of any models that have actually hit the market. These would enable you to read a tag when it is either close to a reader, or five feet away. If you can keep the tag at a distance of 1 foot to 5 feet, that might make things easier for you.
The fact that you are operating within a Faraday cage should also facilitate the process. The cage should keep out extraneous RF energy that could otherwise interfere with tag reads.
—Mark Roberti, Founder and Editor, RFID Journal
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