# method of properly replacing continues wall with VIA rows in STRIPLINE

#### yef smith

Joined Aug 2, 2020
364
Hello, I have a stripline T junction as shown bellow.
there are walls (red ) for absorbind coupling between lines in the network.
the wall goes from top ground to bottum ground as shown in side view bellow.
In real life we need to replace the IDEAL WALL with VIAS.
What are the proper guidelines for VIA RADIUS,the distance between VIAS,distance between VIA and the trace?
I'll be happy to know also the physical logic behind the guideline ,if someone knows.
or some article name i can read to understand the subject.
Thanks.

#### yef smith

Joined Aug 2, 2020
364
Hello drjohsmith,yes i have found your avice in the article you attached.
But the article did not say about reccomended VIA radius ,and the distance between the via and the signal trace.
do you know something about these Via guidlines ?
Thanks.

#### Delta Prime

Joined Nov 15, 2019
1,311
Hello there I hope this helps it helped me.

Last edited:

#### yef smith

Joined Aug 2, 2020
364
Hello Delta Prime,very good manual.
but they dont say the guidelines regarding radius of the VIA.
Thanks.

#### drjohsmith

Joined Dec 13, 2021
423
Hello Delta Prime,very good manual.
but they dont say the guidelines regarding radius of the VIA.
Thanks.
Vias are round, they are drilled .
so the normal is to refer to via diameter.

Think about the "reason" for the vias,
I'd say they are there to electrically connect the grounds together,
There size is thus determined by the current they must take.
The current flowing between the ground planes is caused by the pick up from the signal trace,
which is going to be "next to nothing"
thus the via diameter does not matter,

But

back to the first point
if you put the via fence too near the trace,
then its presence will interfere with the fields around the trace,
and affect the traces impedance
If you put the via fence away from the trace, then it has "no" effect on the trace
as the fields are minimal at that distance
but then, the via fence is doing nothing
apart from adding cost to the board.

If you are using a via fence,
then on the layer the conductor is on,
the fences should be joined by a track to minimize the circulating currents.

To note,
I have only seen via fences used on High power systems,
with many 10's watts of power being transmitted at very high frequency

You are much better off, minimising the gap between the transmission track and the ground plane