2.4 Ghz Antenna Help

[AmaanSingh]

I'm trying to create a 2.4ghz antenna on a 4 layer JLCPB 3313 stackup. I'm using this design. https://www.ti.com/lit/an/swra117d/swra117d.pdf
Right now I used to gerber2ems to convert my kicad pcb to geometry.xml and trying to get the s11 and zin and paraview simulation files. I'm new to this and don't know if what I'm doing is right or wrong. I think the port is misplaced and this is why I'm getting really bad results. I'm not sure if the port should be touching the the feed line or it should be directly on it or really close to it. Also whether if orientation matters, like face into feed line or facing toward into ground plane. Or how big the port should be. I know the antenna would not be tuned compared to the one from ti but I was going to run a script for that optimization afterwards for this particular stackup. Also for stackup, I should consider the soldermask or no? Also need to add via to connect all ground planes.

antenna.1.mp4

[VolkerMuehlhaus]

I'm not sure if the port should be touching the the feed line

Yes, sure, the lumped port must be drawn between the antenna feed and the ground metal. Each port has two terminals. One terminal of the port must touch the feed metal, the other terminal of the port must touch the ground metal. Only then, current can flow.

[AmaanSingh]

How does the ground on the second layer get touched by the ground trace on the antenna or how is the ground on the second layer connected to the first layer. Do i need to connect a via. I connected a via in kicad and then imported into using the freecad export openems macro. And the graph is completely different from creating the geometry in freecad and then in the csxcad adding a via.
So I'm not sure if the kicad one is wrong. Because for the kicad one using the same antenna params for both, I'm getting -23db at the 2.441 frequency and for the one with the via in csxcad, Im getting something like -5. So which one should I trust.

[VolkerMuehlhaus]

It is difficult to understand what you show and what you actually modelled.

• In general, you need to model what you create in hardware. The metal paths in openEMS must be the same as in hardware.
• For the PCB antenna that you show, additional ground layers might have little effect on antenna performance, if the top layer with F antenna + port has large ground already.
• If your model with vias gives wrong results, something is wrong with your model. There are many possible mistakes.

It is important to carefully check the model and mesh in AppCSXCAD, to make sure all (relevant) conductor paths are included properly.