PCB microstrip line capacitance

QuickField simulation example

This is an example of the microstrip line simulation, performed with QuickField software.

Problem Type
Plane-parallel problem of electrostatics.

Geometry

Given
Relative permittivity of air ε = 1;
Relative permittivity of substrate ε = 10.
Shield is grounded U = 0 V.

Task
Determine the capacitance of the microstrip transmission line.

Solution
The capacitance is the ratio of stored electric charge to potential difference between the strip and the shield. We apply electric potential of 1V to the strip.

Result
Microstrip capacitance is 1.77e-10 [C] / 1 [V] = 0.177 [nF] per 1 meter of strip line length.

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