# 3D EM interface to electrical circuits

1. ## 3D EM interface to electrical circuits

The amount of energy that a wire receives (or emits) depends on its impedance. This impedance is a function of the environment around the wire. A wire laid out above the ground plane is an example of this dependency. If we change the distance to the GND plane, the current flowing in the wire (i.e. during emissions) will change. This impedance is generally different from antenna's impedance. CST microwave/DS does not show this impedance, at least explicitly. Is there any 3D EM simulation that can give this impedance? I want to use it directly in pspice.

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2. ## Re: 3D EM interface to electrical circuits

Originally Posted by JalalTN
The amount of energy that a wire receives (or emits) depends on its impedance. This impedance is a function of the environment around the wire.
This is a very simplified view. It is not clear what you are looking for. Are you looking at transmission line impedance basics? Radiation resistance of an antenna?

3. ## Re: 3D EM interface to electrical circuits

Originally Posted by volker@muehlhaus
This is a very simplified view. It is not clear what you are looking for. Are you looking at transmission line impedance basics? Radiation resistance of an antenna?
I'm not interested in the emissions. It is a complicated EM system, not a transmission line. The system goes to a strong unwanted oscillation, at RF frequency! Seems that the oscillation is due to a combination of EM and the detail parameters of the semiconductor. Pspice is needed to address detail of semi.

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4. ## Re: 3D EM interface to electrical circuits

Not sure whether this would be what you need, however my suggestion is to look for sigrity or momentum tool.

5. ## Re: 3D EM interface to electrical circuits

Originally Posted by JalalTN
It is a complicated EM system, not a transmission line. The system goes to a strong unwanted oscillation, at RF frequency! Seems that the oscillation is due to a combination of EM and the detail parameters of the semiconductor. Pspice is needed to address detail of semi.
You mentioned wire, that is why I mentioned distributed circuit parameters (line impedance) rather than nodal parameters.

I think there is no simple "this impedance" value (or concept) that will solve your analysis problem. It's really more involved than that.

Your oscillallation might be from parasitic coupling (positive feedback across multiple stages -> EM analysis) or negative impedance (combined analysis of active + passive circuit + EM).

Originally Posted by Dominik Przyborowski
Not sure whether this would be what you need, however my suggestion is to look for sigrity or momentum tool.
Agreed, but the key issue is the actual use of the EM tool. It seems that JalalTN isn't experienced with using EM results in circuit simulation, and looks for one magic parameter that he can plug into SPICE simulation.

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6. ## Re: 3D EM interface to electrical circuits

I believe CST and another software were tried with no success.

7. ## Re: 3D EM interface to electrical circuits

Originally Posted by JalalTN
I believe CST and another software were tried with no success.
That means nothing. Unexperienced users often don't know how to apply EM tools properly. That's a typical mistake by many groups starting to do EM: they think they just need to buy the tool and have accurate results with no training and no experience.

What you describe sounds like a typical problem that many other have solved successfully.

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