What are the effects of PCB routing on radiated emissions in edge computing boxes?

Edge-box PCB routing is a decisive factor in radiated emissions. Poor routing makes the microstrip antenna effect significant. Specific effects include: excessively large high-frequency signal loop area; discontinuous reference plane; lack of return path for via layer changes; and non-equidistant differential lines leading to increased common-mode radiation. Taking Gigabit Ethernet as an example, the PHY to RJ45 differential line must meet 100Ω impedance control and be connected in series with a common-mode inductor CMZ2012A-900T. Its naming is CM common-mode Z impedance 2012 size 2.0×1.2mm 900T impedance 90Ω 100MHz, and no traces are allowed below the inductor. The power layer and ground layer are tightly coupled. The ferrite bead layout should be close to the chip pins. For example, DDR power uses PBZ1608E600Z0T ferrite beads, named PB ferrite bead Z ordinary 1608 size 1.6×0.8mm E600 impedance 60Ω Z tolerance 0 internal code T packaging to convert high-frequency noise into heat. A good PCB should ensure 20H regularity. The ground spacing of critical signal packets is 3W. Actual measurements show that optimizing PCB routing can reduce overall radiated emissions by 10-15dB.