I would like to simulate a rectangular transmitter coil created in KiCad. Do you know a tool with which I can simulate electromagnetic fields? Preferably free of charge.
Criteria that the program should meet.
Import the coil from KiCad into the program as a 3D file, or it should be as simple as possible.
I agree with @eelik - not simple. You might want to look at https://openems.de/start/ which is a nice EMS solver.
I have not tried this but if I recall correctly, openEMS can read Hyperlynx files which i believe are available as an export option from recent KiCad versions.
EDIT
I have just checked and I think the HyperLynx export is only available in 5.99
You can use fcad_pcb in FreeCad to get step model of board and copper. With geometry in de facto standard interchange format you should be able to use a number of different simulation models
You could also use part of code from Spiki so you could generate geometry for FastHenry. And maybe the Spiki is exactly the tool that you need. But from the sparse description I would guess you want to know the mutual inductance between two coils and I don’t know if you can get that with FastHenry