A two-step methodology for predicting the radiated fields from lines radiating in the presence of conductor-backed substrates is presented. The method employs the use of transmission line theory to find the current distributions on the lines forming the interconnects of a circuit. These currents are used to evaluate the far-fields of the circuit through the use of dipole theory and superposition. The method was tested and validated by comparison to full-wave models. Investigations established that radiation from common-mode currents, which are not accounted for by the circuit analysis, are found to be dominated by the radiation due to differential mode currents, and thus EMI prediction based on the two-step methodology is found to have good engineering accuracy. A full-wave method based on the Finite-Difference Time-Domain (FDTD) is presented for the evaluation of radiation from structures of such geometrical complexity that the transmission line model is not applicable. The Perfectly Matched Layer truncation scheme is implemented in the FDTD and investigated for radiating structures found in printed circuit boards (PCBs). Proximity effects of the PML dictate careful attention to the proper implementation of this absorbing boundary condition. Also, the FDTD subcell model for thin wires is investigated for modelling thin microstrip interconnect lines. To evaluate the far-fields from radiating structures found in multilayer electronic packages, a novel near-to-far field transform at a single frequency is developed and implemented for sources in stratified medium. This transform is validated and investigated with regard to PML and structure proximity. The near-to-far field transform is also implemented in a methodology for obtaining the radiated emissions from a radiating structure. This methodology is used to address important concerns regarding the grounding of heat sinks, "floating" conducting planes, and the electromagnetic behavior of split ground planes.
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