How do I calculate physical distance between RFID reader and TAG

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I have UHF tags and ATID reader, i want the physical distance of reader to tag.. i have RSSI values, But i am unable to measure physical distance. Is there any way to calculate physical distance from tag to reader

What I have tried:

used RSSI to calculate distance but it is changing its value contineously

Posted 11-Jun-16 2:48am

Madhuri Gamane

Updated 11-Jun-16 8:37am

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George Jonsson 11-Jun-16 9:45am

Do you mean that the RSSI value changes even if the tag is at a constant distance?
How much does the RSSI value vary? (In, for example, percent)

Sergey Alexandrovich Kryukov 11-Jun-16 12:55pm

I think that the idea of getting any acceptable accuracy via RSSI is quite hopeless. Please see Solution 1 for some discussion and links.
—SA

George Jonsson 11-Jun-16 20:46pm

You are probably right.
Too many factors that can effect the RSSI value. If the tag is on the front or back on a box, for example.

Sergey Alexandrovich Kryukov 11-Jun-16 21:04pm

Not only that. Interfering waves from several obstacles, which move in to the scene or move out of it as you change the distance — what to talk about? To measure distances, the machinery should have some of the radar's features (please see Solution 1).
—SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2016-06-11T06:51:00

General-purpose RFID physical operation is unsuitable for measuring distances.
The only thing I could think of is this, which you can use with RSSI, but you hardly can hope to get any acceptable accuracy. In radio domain, the principles of measurements are that of radar:
Radar — Wikipedia, the free encyclopedia.

See also these articles:
Readers That Sense Distance — RFID Journal,
RFID-radar — How it works.

—SA

Dave Kreskowiak · Answer 2 · 2016-06-11T08:37:00

Solution 2

No, there is no way for you to measure distance to the tag with any accuracy and/or reliability at all.

The consumer grade RFID technology is just not setup to do that.

Posted 11-Jun-16 8:37am

Dave Kreskowiak

Updated 11-Jun-16 8:39am

v3