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I'm currently working on a design who involve a NFC chip (ST24DV) who need to be on the board as it's used to communicate with a smartphone. Here is the picture of the antenna: enter image description here

There is a LED on the right (yellow circle) I can't move due to mechanical compatibility. When this board is alone, I have no problem communicating with the NFC chip with my smartphone. But this board is supposed to be connected through wires to satellite boards who share the same GND. When these other boards are connected, impossible to detect the NFC chip with my smartphone.

I would like to know if someone have advices about how to overcome this difficulty. Maybe by pushing cooper pour away... but the LED need to stay here.

Another thing is I can't move the antenna too much because it need to be in front of an opening in a case.

Thank you for reading.

Prof_Sims
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  • It sounds like the satellite boards may be generating too much local magnetic noise. – Andy aka Jan 20 '21 at 15:11
  • how exactly are the other boards connected to the NFC board? how are they arranged physically? are they in some kind of stack? could they be interfering with the NFC circuit due to proximity? FWIW I recently completed a project using NFC (different chip though) and once it was working, it was pretty robust. – danmcb Jan 20 '21 at 15:42
  • The wires and gnd plane may be cancelling externally the effects of the antenna. Did you use coax or twisted pairs? Also what fraction of a wavelength is the separation of gnd planes? – Tony Stewart EE75 Jan 20 '21 at 16:15
  • @danmcb The other boards are connecter through 3 meters cables (3 pairs) RJ11 style. Tony so yes, twister pairs because of differential link. I use one pair for the differential link, one wire for 3.3V and 3 others for ground. The distance between the side of the antenna and the ground plane is 3mm. – Prof_Sims Jan 22 '21 at 10:14

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