ATLC (http://atlc.sourceforge.net/) appears to be good #opensource tool to design unusual PCB (micro)strip lines. But slow. P.s. Images of simulated 100 Ω edge coupled embedded #microstrip included.
@vovanium What's shown in the pictures?
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@sunny_qad There are microstrip cross-section (different materials shown in different colours) and its simulation output made by atlc: electric potential and x, y components of electric field.
On first image red and blue are positive and negative conductors respectively, green is ground counductor, yellow is fiberglass, magenta is prepreg, white is air. On other images red is simply a positive value and blue is negative.
