Design for compatibility. The spectrum is a shared resource.
High-frequency currents love the edge of a ground plane. If a signal trace runs near the board edge, its return current crowds the boundary, radiating directly into the environment. emc for printed circuit boards
At its core, EMC is about interrupting the triad of electromagnetic interference (EMI): the Source, the Path, and the Victim. On a PCB, the source is often a high-speed clock, a switching power supply, or a fast-rise-time driver. The victim is a sensitive analog input, a reset line, or a nearby radio receiver. The goal of EMC design is to sever the path between them. Design for compatibility