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* = 1.76e-12 C.

The capacitance is *C12* = 1.76e-12 / (0.5 - (-0.5)) = 1.76e-12 F.

See the *microstrip_crossover.pbm* problem in the Examples folder.