Microstrip crossover - QuickField simulation example

Crossovers in the digital circuit design cause parasitic capacitance, resulting in high frequency cross talk.

How to find PCB microstrip crossover capacitance?

Answer
Set up a 3D QuickField Electrostatics problem for a PCB microstrip crossover and evaluate capacitance from computed field results.

Simulation problem

Problem Type electrostatics.

Geometry 3D extrusion.
microstrip crossover model

Equivalent electric circuit:
microstrip crossover 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.

Task
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 = 1.76e-12 C.
The capacitance is C12 = 1.76e-12 / (0.5 - (-0.5)) = 1.76e-12 F.
microstrip crossover simulation