How do you design avionics equipment for EMI/EMC compliance per DO-160?

DO-160G Section 20-22 defines EMI/EMC requirements. Design strategies: Conducted emissions - filtering power inputs (common-mode chokes, differential filters), proper grounding (single-point or hybrid), and shielded cables for sensitive signals. Radiated emissions - metal enclosures with proper sealing at seams, filtered/shielded connectors, and controlled cable routing. Susceptibility - adequate shielding effectiveness, filtering of all I/O lines, and software tolerance of transients. Specific concerns: HIRF (High Intensity Radiated Fields) from radar, lightning-induced transients, and switching power supply harmonics. Design practices: Use of multi-layer PCBs with ground/power planes, decoupling capacitors at ICs, controlled impedance traces, and proper grounding strategy (star, hybrid). Testing early in development; pre-compliance testing identifies issues. Layout and cable harness design are as critical as circuit design.