Equivalent circuit for coupling between two wire

[zionico90]

Hi guys,

i would try to simulate (in easy way in order to have only an approximate value) the coupling between two wire. The distance is set to 30mm, the diameter is 35um and the length 130mm. I have calculate an inductance equal to 230nH and a capacitance equal to 0.1 pF.
These two wires are grounded on a different reference plane with capacitance 0.5pF. In order to taking into account the isolating between the reference plane i have introduce a higher resistance.
R=500ohm is the source output and R=10Kohm is the external load.

The equivalent model is shown in attachment; is the correct way to simulate this system?

Thank you

p.s: is my first equivalent model circuit

View attachment eq.bmp

 

[FvM]

These two wires are grounded on a different reference plane with capacitance 0.5pF.

Means what? Please clarify the geometry with a picture. The equivalent circuit with 230 H inductors can't be right, also the physical nature of the resistors is dubious.

And don't post uncompressed bitmap images.

 

[zionico90]

Sorry for the bitmap images. The 3D structure is the following:

 

[FvM]

The equivalent circuit is wrong in several regards. The inductance is a series rather than a parallel element. There will be an inductive coupling of both wires.

As a first order estimation, I would use three ideal transmission lines, two single ended modelling the wires above a groundplanes and a differential representing the coupling. It's parameters can be derived from extracted partial L and C elements.

A 2-D electrostatic respectively AC magnetic simulation can be used to extract the L and C elements. I would assume both ground planes shorted for simplification. otherwise a fourth differential TL has to be used in the simulation.

Of course a true 3D EM solver can handle the problem, but the thin wire involves a large meshing effort.

 

[zionico90]

Thank you for the answer. Yes, for the inductance it's a my mistake :shock:

I have also the results by 3D EM simulation but as you have say, the effort for the mesghing is very expensive. I would try to reproduced a first order estimation in order to try to reduce the coupling and finally use the 3D EM to fine simulation.

I try to realize the circuit with 3 TL as you have suggested.

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Can you make a sketch of the circuit?There are some aspect that i don't understand. Thank you