NFC Antenna Frequency

RE: NFC Antenna Frequency

ketiljo — Tue, 04 Nov 2025 09:44:05 GMT

Yes. The reader or initiator is generating a magnetic field that is being modulated by the tag. The frequency can in theory be anything, but to adhere to the standards, the tag antenna resonates at 13.56 MHz.

The nRF52840 NFC peripheral operates the same way as passive NFC tag, like the ones you can find in key cards etc.

RE: NFC Antenna Frequency

Salokmonr — Mon, 03 Nov 2025 14:58:03 GMT

Rgarding frequency tolerance , so to get it clearly , the nRF52840 when he send back information the frequnecy 13.56MHz and tollerance is conrold by the external NFC antnna we design ?

RE: NFC Antenna Frequency

ketiljo — Mon, 03 Nov 2025 13:16:19 GMT

[quote user=""]What is the source of the 13.56 MHz carrier used for the NFC-A tag interface?
– Is the 13.56 MHz generated internally by the SoC, or does it rely on an external circuit to produce the carrier field?[/quote]

The field is produced by the reader (external)

[quote user=""]What is the frequency tolerance of the NFC-A interface as implemented in the nRF52840?
– Is there a specified range (e.g., ±7 kHz per ISO/IEC 14443-2), or does the SoC itself have an internal frequency specification for NFC operation?[/quote]

Frequency tolerance is limited by the bandwidth of the antenna.

[quote user=""]– Does it simply act as a resonant matching network at 13.56 MHz, or does it play a part in generating or shaping the carrier signal amplitude?[/quote]

It's only a resonant circuit.