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Matching circuit required for HF RFID? Fundamental difference between NFC and RFID antennas at 13.56MHz?

Jay Jang
Intellectual 915 points

I have a question about HF RFID.  Do we need a matching circuit for HF RFID?  NFC antenna needs a matching circuit and it is at the same frequency 13.56MHz.  So I’m wondering if it is needed for HF RFID.  But LF RFID at 125KHz or 134.2KHz doesn’t need it.  If a matching circuit is not necessary for RFID regardless of the operation frequency, then is the fundamental difference between NFC and RFID antennas at 13.56MHz?

Thank you,

Jay

  • 0
    TI__Mastermind 44140 points
    Hi Jay,

    For HF transceivers, you typically need to have a matching network. In the case of the TRF79xxA devices, the TX pin is 4 ohms, so we use the matching network to impedance match the 4 ohm impedance to a 50 ohm antenna. See the TRF7970ATB for a example of the matching network recommended. In the case of a transponder(tag), there is not impedance matching required since the transponder only uses load modulation, therefore just a capacitor in parallel to the antenna coil will achieve resonance.