Hello, I want to add a VIA fence to improve the signal of the microstrip shown below. I know that the distance between vias (brown arrow) is lambda/20.
1.what via diameter to use?
2.What the the vertical distance (blue arrow) between the VIAS?
3.If i will put a field monitor on the VIA fence how can i see from the electric field that the VIA fense is working well?
Thanks.

 

The via diameter is largely determined by whatever process you're dealing with (some manufacturers have set via sizes, for instance, or a minimum size) and what frequencies you're working at and what materials you're working with. If this will be manufactured by a PCB shop somewhere, then look up their minimum via size and go with something bigger than that (excluding microvias). If this is going to be on a MMIC, then your via size is probably fixed. If these are GND vias, then you don't have to be as concerned with diameter as if it were a signal via. Maybe start with lambda/40 as your via size and then change it as necessary.

The distance between vias (the gap) depends on a lot of things. If you're going for a 50-ohm line, start with a GCPW or substrate-integrated waveguide (SIW) calculator to figure out a starting gap width (because you've got an approximation of a waveguide here) and then adjust it as you see fit to improve performance (depending on what your target is).

For field monitors to verify the fence is working, there are a couple ways you can do this:
- A planar slice of the structure (the normal vector facing up) halfway down the substrate. This will show you the magnitude of the field everywhere inside and outside the fence.
- A planar slice with the normal parallel to your microstrip line, intersecting a via or between two vias (you'll see different results).

Hope this helps you get started!

 

Hello, I want to add a VIA fence to improve the signal of the microstrip shown below. I know that the distance between vias (brown arrow) is lambda/20.
1.what via diameter to use?
2.What the the vertical distance (blue arrow) between the VIAS?
3.If i will put a field monitor on the VIA fence how can i see from the electric field that the VIA fense is working well?
Thanks.



View attachment 298119

out of interest
why do you think you need to improve the signal with a via fence, and how much do you want to improve what by

 

Any "Gain-Increase" not related to better Impedance-Matching of the "System"
will result in a loss of Gain in some particular direction of RF-Radiation.

This might be a bonus,
but in certain situations it may also be a detriment.

Extensive testing is required to determine if the change will be beneficial, or a disaster.
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