It's been a few years since I looked for free software. I assume you have used it and will have a look. Which tools did you use with it?
So far I've been using openEMS only through
QucsStudio, which automatically generates the 3D model and simulation script, and runs it. However, this limits you to microstrip structures, i.e., planar copper over a solid ground plane. But it has the benefit that the EM simulation is integrated in a circuit simulator, so you can add lumped elements and other structures very easily. I've been using it to tweak microstrip filters, bias tees and couplers, which works very well. Up to now this has been covering all my needs.
To simulate waveguide structures and devices, or antennas, with openEMS you would need a 3D cad like
FreeCAD, and Octave to write and run the simulation scripts. If you only want frequency domain data like S-parameters, you could use Octave's own plotting functions, or dump the S-parameter data to a file, e.g. in Touchstone format, by setting up a script to do that. If you want animated field visualizations it is my understanding that you need something like
ParaView, as has been shown in the videos.
Some time ago I've been looking at openEMS's documentation and examples. It is my impression that if you know some Matlab/Octave, the scripting part is not rocket science. You have to gain some understanding of FDTD simulations though, in order to set up things like the mesh and the excitation (frequency range, decay energy, etc.), as well as material properties, to get reliable results in finite time. But that is already the case for microstrip with QucsStudio, even though there are far less degrees of freedom.
If I were to venture into this area, I would have to learn some 3D CAD first.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
To get started with openEMS it would probably be a a good idea to get some of the examples on the homepage working and then tweak them. Too bad it is down at the moment, there is only the Github stuff available. But there is certainly a steep learning curve involved, as with many things related to electronics, and there is never enough time in life (I'm currently trying to get my head wrapped around Verilog and Lattice FPGAs).
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