How the GND plane affect the antenna beam direction?

[tony_lth]

Hi, Gurus,
Attachment is one antenna design of TI 77GHz demo board.
I have a question about the GND definition.
In HFSS simulation, we directly define the bottom layer as the perfect E plane.
But in real, the bottom under the antenna patches are a big plane of copper, only the edge of the plane are linked to GND with vias.
We can't place via directly under the antenna patches.
So what is the difference between the simulation and the reality?
Best,
Tony Liu

 

[PlanarMetamaterials]

One aspect of irregular bonding of the upper and lower "ground planes" is that they generally don't have the same potential, and therefore support electric fields -- i.e., propagating modes -- between them. Generally, you don't want this, so you place more vias to suppress these modes.

In patch antennas, like the ones you've shown, you do indeed want to support a mode between the upper and lower conductors -- so of course there will be no vias.

Ideally, there is no difference between simulation and reality, but of course, this this statement does not reflect reality