If an RFID tag is placed on a metallic object, does it absorb RF energy from a reader and reflect it, resulting in a reduced read range? I need to have a clear idea about how RFID tags are affected when they are placed on metal.
If you were to take an ordinary passive RFID transponder and place it on a metal object, the metal would detune the antenna. This is similar to what happens when you take an AM or FM radio and touch the antenna with a piece of metal. The antenna is no longer tuned to the frequency of the incoming radio waves, so you don’t get good radio reception. Similarly, the RFID tag antenna will no longer be tuned to receive radio waves from the reader, and will be rendered unreadable or have an extremely short read range.
RFID tag providers have gotten around this problem by designing tags with tiny spacers that lift the antenna off the metal object. There are many different types of on-metal tags, but I think it is fair to say that tagging metal objects with passive RFID is not difficult. Marks & Spencer, a British retailer, is tagging many metal objects, including pots and pans (see Marks & Spencer Embraces Change). And Age Steel is tagging sheets of steel in a laydown yard (see RFID-Reading Drone Tracks Structural Steel Products in Storage Yard).
—Mark Roberti, Founder and Editor, RFID Journal
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