That’s an interesting question. If you are asking whether you can determine the orientation of any tag with any reader, the answer is no. But there are ways you could use an RFID system to determine an object’s orientation.
Let’s say you had a metal box and you put a passive ultrahigh-frequency (UHF) transponder designed to work on metal on the top of that box, and a reader antenna above it. If you were able to read the tag, you could determine that, for instance, the box was sitting upright. If the box was upside down, the tag would be blocked by the metal and would not be readable. You could put multiple tags on the sides of the box to ascertain its orientation.
If you were to use a UHF transponder with a dipole antenna and a linear polarized antenna, the tag could be read only when the antenna was aligned with the reader antenna. That is, if the tag antenna was vertical and the reader antenna was horizontal, then the tag would not be read. And if the tag antenna were perpendicular to the reader antenna, it would also not be read. So you could use a dipole reader and a linear polarized antenna to determine an object’s orientation in some applications.
Of course, not reading the tag might be a bad thing, so you might need to have two tags, one with an orientation-insensitive antenna and one with a dipole. The orientation-insensitive tag would identify the object, while the dipole would be used to determine its orientation. If any of our readers have examples of systems that can be used to identify an object’s orientation, they are invited to please post a description below.
—Mark Roberti, Founder and Editor, RFID Journal
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