I am new to wireless communication and am trying to use a CR95HF to create a NFC reader/writer. How do I decide the geometry and size to make the trace antenna for the CR95HF?

[KFran.2]

The external antenna being read is circular (32mm in diameter). During use the external antenna will be within 6in from the reader/writer circuit I am creating.

[Brian TIDAL]

Hi,

for new reference designs, we recommend to use the ST25R95 (see Differences between ST95HF and ST25R95), except if you plan to use the UART communication mode.

For the design of the RF part, you can refer to the AN5248 ST25R95 transceiver antenna tuning circuit with EMI filter 1.1 Application Note for the matching circuit and to https://eds.st.com/antenna for the design of a rectangular antenna. As you plan to use a circular antenna, I need to check for specific support.

Rgds

BT

[KFran.2]

Hi BT,

Thank you for the quick reply and reference documentation! Do I need to use a circular antenna for my design? Can I create a rectangular antenna on my reader/writer circuit and still communicate with DUTs that has a circular NFC antenna? Or do I limit myself to use only DUTs that have the same antenna geometry as my NFC antenna?

Thank you,

KF

[Brian TIDAL · Accepted solution]

Hi,

on my side, I have different setup (such as X-NUCLEO-NFC03A1) with rectangular or square antennas and I am able to communicate with tags having different antennas including circular antenna. Do not hesitate to order a X-NUCLEO-NFC03A1 + NUCLEO-L476 kit to assess the reading capability with your tag.

Rgds

BT