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Presently, my problem is that I have this NFC/RFID Tag, and due to the small antenna on the tag, it needs to make direct contact with the reader (presently tested using both a smartphone w/ NFC capabilities, as well as a cheap HF RFID reader module connected to an Arduino UNO).

My project requires an extremely small NFC/HF RFID tag that can be read from about 1-2mm, through a layer of material. For an easier visual understanding, it is as if the reader is in your pocket, and it would have to pick up the tag through the material. Presently, this is just thick enough that I cannot get consistent results.

So my question is - is it physically impossible for me to ever read this tag given my constraints? Or, would increasing my read range help at all? Not sure how I would amplify my range on the smartphone, but I'd imagine a different antenna on the HF Reader would do the trick there.

If it is a matter of physical limitations, is there an alternative I am not thinking of? NFC/RFID is not an absolute requirement, as I am not trying to read data off the tag. I am using the presence of the tag within the reader's field to trigger an event, and I cannot think of a better technology that could potentially identify something that is so small/discreet nearby without being within a direct line of sight. So if there are any suggestions for an alternative, I am more than willing to modify my design to accommodate. Likewise, I am not tied to this particular tag if there exists a better one of comparable dimensions.

Thanks in advance for any suggestions/references!

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  • \$\begingroup\$ It should be noted that the reason NFC is called near-field communication is because it only works with the two devices near each other. That said, reading through a pocket (which I would assume to be 1-2mm thick, not 1-2cm, is that a typo?) should be perfectly possible. \$\endgroup\$
    – Hearth
    Feb 1, 2019 at 19:10
  • \$\begingroup\$ I corrected it, I had meant to say mm, not cm, so thank you. Regardless, the tag can be read (barely) through a pocket, and the goal is to increase consistency of that read. Currently, it takes a lot of hard pressing and moving around for the tag to be identified, whereas the goal of the project is for the motion of the tag to be more fluid (not painstaking by constantly fiddling with the position). I think this may just be a limitation of the tag I have. However, I need a tag of those dimensions (or thereabout) that can be consistently read through a pocket \$\endgroup\$
    – KC Ford
    Feb 1, 2019 at 19:20
  • \$\begingroup\$ your going to probably have to look for another tag......direct quote " Note that since the antenna is so small you'll need to put the tag right up against the device that's reading it." the only other thing i can think of use a directional antenna on the reader if possible. \$\endgroup\$
    – jsolarski
    Feb 1, 2019 at 22:55

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RFID tags such as these depend on the antenna to not only receive and send the signal, but the antenna must inductively capture enough of the power from the transponder to wake up and transmit back. This means that the orientation of the antenna, which in this case is just a spiral piece of foil, must be perpendicular to the "lines of flux" of the transmitter's local magnetic field. If they are parallel, you are out of luck regardless of distance.

Depending on what you are trying to do, you might experiment with three tags glued together such that they face in three axes - chances are that one or two will be able to respond. A more powerful transmitter increases your chances when the angle is not ideal. Good luck!

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