Analysis of Radiated Emission in Multi-Microstrip Lines above Finite Size Ground Plane

This paper presents an analytical model for the electromagnetic radiation in multi-microstrip lines covering the frequency range from 30 MHz to 1 GHz. The radiated emissions of multi-microstrip structure can be divided into the summation of radiated emissions of multi-individual microstrip structures. It is done by modelling the imperfect ground effect of the PCBs. Here we present a circuit model based on traditional transmission lines (TMLs) model. For more accurate analysis of the imperfect ground effect in multi-microstrip lines, we will divide the equivalent circuit model into N sections, based on transverse electromagnetic (TEM) assumption, to estimate the electromagnetic interference (EMI) of multi-microstrip lines. The quantitative value of induced current distribution along the ground return path depends on the physical size, geometry and length of ground trace. Measured data are presented to confirm the results of numerical analysis and the computer simulations with a software package based on the Finite Element Method. A knowledge of EMI source mechanism and their relationship to layout geometries is necessary to determine the essential features that must be modelled to estimate emissions in PCBs design.