Are there example antenna layouts that have been tested?

[smithderek2000]

Hello,

I am working on a system whereby I need an antenna no wider than 20mm, can be 30mm long. Rather than making my own (and possibly messing it up) I was wondering whether you had example antenna layouts that have been designed before. Currently looking at using the ST25R11 because of the automatic antenna tuning, but could be open to alternate readers. Need to read a tag 20mm in diameter at a distance of approximately 20mm.

Thanks

[Travis Palmer · Accepted solution]

Hello Derek,

dependent on the environment (e.g. metal) the antenna parameter can change. Also in order to adjust the output power a different target matching impedance might be required. This means, that it is not easily possible to specify a normal NFC antenna which can be used by any reader.

There is one exception: 50Ohm NFC antennas.

Those antennas are already equipped with damping resistor, series and parallel capacitor and tuned to 50Ohm at 13.56MHz.

Such antennas can be connected to a reader which has a matching network for 50Ohm antennas.

There is the ST25R antenna matching tool which helps you calculating all required component values.

in addition AN5276 and AN5592 are helping you finding the correct antenna.

You should also look at the antenna inductance calculation tool (https://eds.st.com/antenna/#/).

Unfortunately, the parameters required for the ST25R antenna matching tool have to be measured.

BR Travis