Hello people,
Just a general question. I was looking at some PCB NFC antenna design from NXP and I have noticed that they go in an interesting fashion.
Lets say I have a 3 loop NFC PCB antenna. It looks like NXP route half of the first loop before jumping into the second with a via and half of the second before jumping to the third by via, the third loop is finished before returning to the second half of the second loop and then it return to the second half of the first loop [Something like this photo
http://www.entras.cz/images/foto/microcontroller/IMG_1440_up.jpg ]. Why is it routed like this, I was expecting something like it finish the first loop and jump to the second without any via and then finish the second loop and jump to the third without any via and then finish the third and return to the beginning with two vias something like this
https://b2bsol.panasonic.biz/semi-spt/apl/en/tool/nfcdesignnavigator/image/Caution_Gerber.JPGApparently both approaches are widely used but I see the former more, what is the reason of doing that. What advantages does it have, any reference when designing the shape of an NFC antenna.
Also I have seen some commercial NFC antenna where the middle of the tracks is connected to GND, why is that so like when it goes through half of the antenna, the track is connected to GND using a VIA before returning to the start, why is that.
I would really appreciate if anybody helped with these two question. A referenced answer where I can read more from the sources would be great, as I am having trouble finding a good source for general practises used when designing NFC antenna.
Thanks !.