Transline5: simulating coplanar waveguide with microstrip ground

[wernerb]

Hi all

I tried to simulate a CPW with additional microstrip ground (backside ground) using the newly introduced free cross section simulator (“Beliebiger Querschnitt”). This produces wrong results, if the gap between hot conductor (center) and topside ground gets small. The formula-based model (“Koplanar-Leitung mit Rückseite”) yields reasonable results.

This is the simulation model:

% Microstrip with CPW ground

unit mm

@h=0.5 %substrate height

@h1=0.25 %lower substrate height

@h2=0.25 %upper substrate height

@w1=0.52 %conductor half width

@w2=0.62 %upper ground opening half width

@t=0.02 %conductor thickness

@a=10 %air space above substrate

@b=10 %structure half width

Air: 1 0 azure -b/h1+h2 -w1/h1+h2 -w1/h1+h2+t w1/h1+h2+t w1/h1+h2 b/h1+h2 b/h1+h2+a -b/h1+h2+a

Conductor: signal 1e-8 red -w1/h1+h2 w1/h1+h2 w1/h1+h2+t -w1/h1+h2+t

Substrate2: 3.66 4e-3 yellow -b/0 b/0 b/h1+h2 -b/h1+h2

Ground1: gnd 1e-8 orange -b/0 b/0

Ground2: gnd 1e-8 orange -b/h1+h2 -w2/h1+h2

Ground3: gnd 1e-8 orange w2/h1+h2 b/h1+h2

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