I have two passive ultrahigh-frequency readers, one fixed and the other mobile, and I want to use the value of RSSI and reference tags to obtain the accurate position of a tag. Can you suggest a way to do such a thing?
It would be very difficult to locate a passive UHF RFID tag precisely within a 3D space using the received signal strength indicator (RSSI), because passive UHF radio waves bounce off walls, ceilings, floors and objects in a room and arrive at the reader at different times. Most handheld readers use RSSI to determine a tag's relative proximity. The handheld reader beeps more often or more loudly as the tag's signal gets stronger. But detecting a stronger or weaker signal is different than determining a tag's precise location.
It might be possible to combine RFID and other technologies, such as reflected laser light, to determine a tag's precise distance from the reader. If you use RFID to locate the object and then hit it with a beam of light, you could probably calculate the distance based on the amount of time it takes for the light to hit the object and then return to the reader.
—Mark Roberti, Founder and Editor, RFID Journal
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