Identification and Characterization of Internal and External Sources of Electromagnetic Compatibility (EMC) Issues in Complex Circuits

Abstract

Electromagnetic compatibility challenges are persistent in increasingly dense electronic platforms where mixed-signal, power conversion, and wireless subsystems coexist. As integration rises, coupling paths multiply across conductors, dielectric volumes, and free space, while device-level switching edges sharpen and spectral content broadens. In this context, distinguishing internal and external sources of disruption and attributing observed emissions or susceptibility to specific mechanisms is necessary for practical design iteration. This paper investigates internal sources such as digital edge transitions, clock-distribution skew, switched-mode power converters, and substrate or ground-network resonances, as well as external sources including intentional radiators, conducted disturbances on harnesses, and ambient impulsive fields. A modeling framework is developed that links field-theoretic representations, circuit reductions, and measurement artifacts to a common set of parameters that can be extracted with moderate effort. The analysis emphasizes bandwidth-aware decomposition of interference, the role of impedances seen by aggressors and victims, and the influence of geometry on modal content. A measurement and diagnostics section discusses probing strategies, calibration drift, and fixture parasitics, with attention to reconstruction of equivalent sources from partial observations. A final section translates the characterization into layout and filtering strategies, power distribution design, and shielding tradeoffs. The objective is to provide a neutral, technically grounded account of identification and characterization practices that scale from board to small system level without presupposing a single numerical method or instrument, thereby supporting reproducible reasoning from root-cause hypotheses to mitigation decisions.