Matching network circuitry for NFC in NRF52840-QIAA-T

RE: Matching network circuitry for NFC in NRF52840-QIAA-T

Simonr — Wed, 30 Sep 2020 13:17:48 GMT

The only thing that's necesary is the tuning caps, and the rest is built onto the chip. EMC filtering for instance, is only necessary for a NFC reader, which the nRF52 devices don't support.

The inductance in the antenna is what matters for the NFC antenna. Since the antenna is differential, it's better to use a two pin connection instead of U:FL which is a single ended connection.

The inductance of the antenna together with the NFC antenna tuning capacitors forms a resonant circuit that is tuned to the NFC frequency, 13.56 MHz. Any change in the connection wires to the antenna can be compensated with the tuning caps.

Best regards,

Simon

RE: Matching network circuitry for NFC in NRF52840-QIAA-T

Sing Yew Chan — Wed, 30 Sep 2020 09:14:20 GMT

Hi Simonr, I have checked out the whitepaper before posting the question here. Since only the LC tank available to tune for the frequency in the whitepaper, i am wondering is there any EMC filtering circuitry needed and any circuitry needed to control the Q factor or the NFC chip is smart to do all the filtering inside the chip ?

Besides that, I also wondering about the characteristic impedance of the NFC antenna traces and any impedance matching network needed ?

Regards,

Sing Yew ( Jason)

RE: Matching network circuitry for NFC in NRF52840-QIAA-T

Simonr — Wed, 30 Sep 2020 08:43:27 GMT

Please check out our NFC antenna tuning whitepaper, which should provide all the information you need on the NFC antenna tuning process for the nRF52 series.

Best regards,

Simon