Keep high-speed traces at least 5x the trace width away from the board edge. Stitch a "guard ring" of vias around the perimeter. Stack-up Strategy: The Foundation of EMC Your layer stack-up is not a cost negotiation; it is an EMC decision. For a 4-layer board, the classic "signal - GND - power - signal" stack-up is excellent. The critical detail: the power and ground planes must be tightly coupled (thin dielectric, < 5 mils) to create a high-frequency decoupling capacitor across the entire board.
Your next PCB will emit noise. The question is: will you design it to, or will you tame it? Design for compatibility. The spectrum is a shared resource. emc for printed circuit boards
Terminate all unused pads, keep test points in-line, or remove stubs longer than 1/10th of the signal’s rise time edge length. 3. The Unfiltered I/O Cable Your board may be perfectly quiet internally, but every cable connected to it—USB, Ethernet, power input—acts as a monopole antenna. Common-mode noise on the internal ground plane couples onto the cable shield or the signal wires, turning the cable into a broadcast tower. Keep high-speed traces at least 5x the trace