Further information on double sided NFC Antennas for ST25DV

[PSaal.1]

Dear Community,

as a hardware developer I'm working on a project with ST25DV Tag.

Now I'm facing some problems with the NFC Antenna and would like to try out some double sided ones. I have some example boards and also a list of ST approved antennas but I want to fit the antenna size to my application. That's why I need some formula to calculate.

Unfortunately, I can't find any useful information on designing double sided antennas.

Do you have any experience with it or do you know good whitepapers or tools to calculate?

Of course I know the ST Antenna calculating tool but that's only for single sided antennas.

Thank you very much!

[PSaal.1]

In February ST published AN5605 "Design of a 13.56 MHz double-layer antenna".

I followed this "cookbook" to design a double-layer antenna.

The needed formula is quite easy and works well with the eDesigns suite.

Only drawback is the missing value for the "k" factor. It is only given for PCB thickness of 0.1 to 0.8mm.

I was using standard FR4 with 1.6mm.

Thus, I took a couple of turns more than needed. It is easy to remove a couple of turns than to add them.

Indeed I needed to remove a lot of turns to match the resonance frequency.

Finally, I figured out that in my case for my antenna with 1.6mm thickness k equals approx. 0.4.

Good luck with designing double layer antennas.

[JDirk.1]

thank you very much for sharing the information