
Crossovers in the digital circuit design cause parasitic capacitance, resulting in high frequency cross talk.
Problem Type:
3D problem of electrostatics.
Geometry:
Equivalent electric circuit:
Given:
Relative permittivity of air ε = 1,
Relative permittivity of substrate ε = 10,
Strip1 potential U1 = 0.5 V,
Strip2 potential U2 = +0.5 V.
Problem:
Find the mutual capacitance between strips C12.
Solution:
To find the mutual capacitances C12 we should switch off all voltage sources and apply opposite potentials on stip1 and stip2.
QuickField simulation gives charge q distribution. The capacitance then can be calculated as C = q / (U2  U1).
Results:
The measured charge q = 1.76e12 C.
The capacitance is C12 = 1.76e12 / (0.5  (0.5)) = 1.76e12 F.
See the microstrip_crossover.pbm problem in the Examples folder.