it is a via fence, also called a picket fence, is a structure used in planar electronic circuit technologies to improve isolation between components which would otherwise be coupled by electromagnetic fields. It consists of a row of via holes which, if spaced close enough together, form a barrier to electromagnetic wave propagation of slab modes in the substrate. Additionally if radiation in the air above the board is also to be suppressed, then a strip pad with via fence allows a shielding can to be electrically attached to the top side, but electrically behave as if it continued through the PCB.
Is this a co-planar design? If so then the route needs a controlled distance from the layer to ground on the same layer with a side wall shield and contiguous ground under the routing. This is analogous to a coax type of wiring. here's the calculations for a top co-planar design: https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm Attaching photo of a co-planar design. Controller impedance at GHz is required.
Is this a co-planar design? If so then the route needs a controlled distance from the layer to ground on the same layer with a side wall shield and contiguous ground under the routing. This is analogous to a coax type of wiring. here's the calculations for a top co-planar design: https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm Attaching photo of a co-planar design.
I agree with Michele. But to offer a little more explanation, consider the board design in 3 dimensions like a room in your house. The top copper layer is the ceiling and the bottom copper layer is the floor. These layers isolate the antenna from the outside world from the top and bottom directions. They can prevent the signal from radiating outward and prevent outside signals from coupling to the pcb trace.
The vias are conductive barrels that stitch the top and bottom copper layers together. Because they are conductive all the way through, they work together to form the walls of the "room". The walls do not need to be solid though. The spacing and size depends on the wavelengths of interest.
Hopefully this helps explain a little more.
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lancelot
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