Ground definition in CST

Hello:
usually the gound on lower side of the substrate is of thickness .03-.05mm. But if in the tutorial of CSt "rectangular patcha antena", ground is about 3mm.
It seem that thickness of ground plane has no effect on the result or i am missing somthing.

Another quesiton:
What should be the length of coaxial feed in CST

Hi,
The 3 mm thickness for ground plate assumed suporrting (Aluminum) plate for it, and I believe that it is not important, if ground is large.

Regards
KMPA

Dear KMPA:
The material used for ground is PEC. The manual of CST says that it need atleast three time steps before it excite the patch.

Hi KMPA:
Yes you r quite right, "Thickness of Ground plane do not effect the results much", Althoug it increases the simulation time.

Theoretically, you are wrong.
The thickness should be ? λ, otherwise surface currents on the thick face will radiate and deform the radiation pattern.

I guess in this case the thickness is ? λ, and that is why you see no difference in the results.

P.

for perfect electric conductor, the current would flow/concentrate on the surface.

Hi Lousy:
Can u explain it bit more

for perfect electric conductor, the current would flow/concentrate on the surface.



Thanks

It should be at least three time steps and <<lamda.

the reason for the thickness is to make the solve time quicker for the tutorial.

As mentioned before, CST needs at least 3 homogenous cells in the direction of the propogation of a port, therefore for a coax feed it needs to be long. If you constructed a full connector with a thin wall etc then you would have small cells --> small time step. This is why a 3mm groundplane is used in this example.

Hope this helps.

Hi

here is latest on ground plane with MICROSTRIPES, 3D EM Solution version 7.5

In version 7.5, ground planes can also be used for models without meshing all of the space between the system and ground plane. A specific algorithm accounts for the effects of the ground plane outside of the simulation domain, substantially reducing solution time.

hope this helps
AW