How to reduce radiation in the clock and bus wiring of a smart controller (PAC)?

To reduce clock and bus wiring radiation in intelligent controllers (PACs), a comprehensive wiring strategy is required. Clock lines should be prioritized for inner layers, referencing a complete ground plane, with the shortest possible trace length and avoiding 90° corners (using 45° or arcs instead). Bus wiring should be grouped, with signals within each group of equal length (error less than 50mil), and ground lines used for isolation between groups. Damping resistors (e.g., 22Ω) or ferrite beads (e.g., PBZ1005B-501Z0T) should be connected in series at the clock and high-speed bus driver ends to mitigate edge noise. For differential buses (e.g., USB, Ethernet), differential pairs should be kept of equal length and spacing, with a spacing less than twice the line width. Local grounding copper foil or shielding should be placed above the wiring area. Simultaneously, spread spectrum clock (SSC) technology should be used to disperse energy. Actual measurements show that after optimizing the wiring, clock harmonic radiation is reduced by 15dB, and bus radiation in the 30MHz-1GHz band is 8dB below the EN55032 Class B limit, passing the IEC61000-4-3 radiated immunity test.