How to set the ground of CPWG?

Hi,I am doing a CPWG design.

I wonder whether my ground setting is right or not.

(pic1.png)

I import the gerber file in ads layout. It has two layers, top metal and via(octangle shape).

At the em setup, I map the conductor via in the substrate, setting the hole to the hole(5) layer.
(pic2.png)

Back to the layout, I select all the octangle via and set them to the hole:drawing layer.

Is my setting right??


I find there is a tab Insert ground on the toolbar.
Can I insert a ground pin and don't place via holes??

( pic3.png)

附图/附件

pic1.png

pic3.png

pic2.png

> (pic1.png)

Placing ground symbols in the layout will not have any effect. You better create a physical connection from the side grounds to the bottom ground plane (i.e. draw physical via).

> At the em setup, I map the conductor via in the substrate, setting the hole to the hole(5) layer.
> (pic2.png)
>
> Back to the layout, I select all the octangle via and set them to the hole:drawing layer.
>
> Is my setting right??

Yes, this modelling approach looks right. You can double check in the 3D EM preview to make sure the vias are indeed included in the EM model.

For the vertical line (from north side) there is no via fence over quite some length, so the side grounds can be at rather different potential than the bottom ground. But that is what you have in layout - and Momentum will show if this is causing issues or not.


> I find there is a tab Insert ground on the toolbar.
> Can I insert a ground pin and don't place via holes??

No. For Momentum you need physical (drawn) vias.

> Yes, this modelling approach looks right. You can double check in the 3D EM preview to make sure the vias are indeed included in the EM model.
>
> For the vertical line (from north side) there is no via fence over quite some length, so the side grounds can be at rather different potential than the bottom ground. But that is what you have in layout - and Momentum will show if this is causing issues or not.
>

Hi volker_muehlhaus :
I attach my em preview. Are the vias included in the EM model?
You say there is no via fence over quite some length, and is it the yellow part??

Thank you~

附图/附件

empreview.png

> I attach my em preview. Are the vias included in the EM model?

Yes, we *see* them in the 3D view, so they *are* included.
Layers that are not mapped in the EM substrate will not be visible in the 3D view.

> You say there is no via fence over quite some length, and is it the yellow part??

Yes, that is what I meant. I don't know the frequency in that part of the circuit, but for example the SMD part connected to the top ground there has no direct connection to the bottom ground. Also, for the input to that line, the PCB does not connect top and bottom grounds. This means that griund current flow there can require a long path until it can flow from top to bottom. This can (will) cause trouble, depending on frequency.

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