Impact on radiated emissions of printed circuit board stitching

The use of closely-spaced vias, or "stitching", is used to reduce radiated emissions from the edge of a printed circuit board (PCB). However, this stitching, by confining the electromagnetic noise to the PCB internals instead of allowing it to radiate, causes undesirable effects by coupling to internal traces and vias. Internal traces connected to outside traces and components provide a second path for radiation, in addition to the edge radiation that stitching is intended to suppress.