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[FAQ] RF37S114: I cannot read this tag with my Android device, why?

Part Number: RF37S114

If you are working on evaluation of the RF37S114 ISO15693 transponders for your application, you may have discovered the tag is not readable by Android phones, proprietary readers, or sometimes even TI's own NFC/RFID Reader kits. Why is that?

  • The RF37S114 is a very small transponder, measuring 4mm by 4mm. This creates a challenge when reading the tag due to how NFC/RFID technology functions, especially since the RF37S114 is a passive tag which must siphon its power from the RF field.

    Communication between readers (transceivers) and tags (transponders) occurs by sending data across an RF field. This RF field is generated by the reader and output from an inductive antenna coil. In order for a tag to be able to receive both power and data from the reader, the antenna coil for the tag needs to couple with the inductive coil from the reader. When this occurs, power and data can be transferred from reader to tag.

    Because the RF37S114 has a very small antenna area, getting sufficient coupling requires a small antenna on the reader as well. Ultimately, most Android phones and many over-the-counter NFC reader solutions have antennas too large to read the tag.

    Optimized antennas sizes for reading the tag are square antennas between 20-25 mm in length per side. The following Application Report covers the expected tag performance based on various antenna sizes tested: