What kind of RFID reader can be used to design a smart shelf able to read the tags of books placed upon it?
You could use either passive high-frequency (HF) or ultrahigh-frequency (UHF) tags for a smart shelf. Which choice is better would depend on many different factors. Here are a few to consider:
Read field: It's easier to create a well-defined read field with HF tags, rather than UHF tags. A coiled antenna in the HF reader creates an electromagnetic field with the coiled antenna in the HF tag. You could limit the read field so nothing beyond, say, 1 foot would be interrogated. With UHF systems, the reader typically emits energy that can excite a tag beyond the area in which you want to read tags. You can take steps to address this, such as powering down the reader antenna to reduce the depth of the read field, or filtering out reads you don't want via software. But generally speaking, HF is better if you want a clearly defined read field (that is, if you want to interrogate only tags on one shelf, and not also on the one above or below it).
Cost: If you have a lot of books, then tag costs can be significant. In general, HF tags cost more than UHF. So this might be an important factor to consider.
Other applications: If you are only building a smart shelf and plan to utilize RFID in other ways for other applications, then you should consider that as well. For example, if you planned to read tags on boxes stored within a warehouse containing high shelving, then you would likely require UHF, which has a longer read range than HF. You would probably want to stick with UHF for the smart shelf as well, to avoid having to deal with two different systems. If, on the other hand, you intended to employ HF tags for a checkout kiosk, then you would want to stick with HF for the smart shelf.
There might be other factors to consider, including ease of integration with your existing back-end system, the availability of qualified RFID professionals to install the systems, and so forth. If you need a consultant or systems integrators to help you sort through these issues, feel free to e-mail me directly at firstname.lastname@example.org.
—Mark Roberti, Founder and Editor, RFID Journal
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