infinite ground plane

Hi

i am just wondering why there is infinite ground plane assumption in some of EM simulators like ansoft designer or Zeland's IE3D.

as a result we cant get accuarate results for structures with finite ground planes.

what benefits these software vendors get when they use this assumption?

i will appreciate any comments on this topic.


regards

hello guys


no one is commenting on this question.

is it too simple or too difficult?

any comments welcome


regards

Shahid:

The infinite ground plane assumption is implicit in the planar EM simulators that operate in an "open" simulation environment. The MoM solution that they use is based on the assumption of an infinite ground plane, so it's part of the math that they are using. You can model finite ground planes in them, but you have to explicitly draw the finite ground plane and simulate it as a separate meshed conductor. So these finite ground plane problems can sometimes require a large amount of memory to solve.

However, if you have an antenna element that is very near the truncated edge of a substrate, the planar simulators cannot model this unless you use one of the simulators that models dielectric blocks or bricks to simulate air along the edge of the dielectric. This might work for simple models, but I don't think you can push it too far.

I would probably look for a full 3D time-domain simulation approach for finite ground plane simulations. I think they are a bit more efficient for antenna problems--especially for wideband analysis.

In Ansoft products you can have finite ground, by un-checking the related box in the assign excitation dialog box. In fact infinite ground for electrically large antenas is some what real. the small size over large ground, with high conductivity, that is a perfect mirror for EM radiation.

mtu:

Is that true for the planar solver in Ansoft Designer?

In many cases, you can consider a finite ground plane to be infinite for large antenna systems. However, I think a thorough antenna designer wants to make sure that edge currents flowing on even large ground plane areas are not adversely affecting the antenna pattern. This can be especially true for phase array antenna systems.

I agree that infinite ground planes are sufficient as a first-order approximation.

Shahid

I am using HFSS, and not sure about designer but think it should be there.

Irfan

infinite ground plane is an assumption that you assume a face as infinite plane and this cause that fields will be different from ungrounded face .and for perfect e you only can assign tree infinite ground plane.

In Designer Planar EM, any layer specified as a Ground layer is infinite in x-y extents. If you specify a layer as a Signal, then you can draw the ground pattern on this layer, ant it becomes part of the MoM mesh. Otherwise, for Ground Layers, if nothing is drawn on them, then they don't add any triangles to the simulation. Anything drawn on a Ground layer will be treated as a aperture, or opening in the ground metal.