Abstract
Electromagnetic bandgap structures are considered a viable solution for the problem of switching noise in printed circuit boards and packages. Less attention, however, has been given to whether or not the introduction of EBGs affects the EMI potential of the circuit to couple unwanted energy to neighboring layers or interconnects. In this paper, we show that the bandgap of EBG structures, as generated using the Brillouin diagram, does not necessarily correspond to the suppression bandwidth typically generated usingS-parameters. We show that the reactive near fields radiating from openings within the EBG layers can be substantial and are present in the entire frequency band including propagating and nonpropagating mode regions. These fields decay fast with distance; however, they can couple significant energy to adjacent layers and to signal lines. The findings are validated using full-wave three-dimensional numerical simulation. Based on this work, design guidelines for EBG structures can be drawn to insure not only suppression of switching noise but also minimization of EMI and insuring signal integrity.
Highlights
The interests to implement electromagnetic bandgap (EBG) structures as a viable solution to reduce electromagnetic interference (EMI) and control switching noise are increasing
It is important for EMI/EMC engineers who are interested in the functionality and signal integrity aspects of EBG design to consider that an effective suppression band between two ports is not necessarily equivalent to a bandgap
Planar EBG patterning of the package or board layer reduces unwanted waves propagating through these structures in the effective suppression band, significantly minimizing the potential for switching noise
Summary
The interests to implement electromagnetic bandgap (EBG) structures as a viable solution to reduce electromagnetic interference (EMI) and control switching noise are increasing. Later studies in [5] showed that the extracted dispersion diagrams for the unit cell of infinite one-dimensional EBG array based on an equivalent circuit model and numerical simulation demonstrated the presence of propagating modes within the suppression band. We analyze the power loss and power transfer between two points in the presence of EBG structures This analysis provides a better understanding of the mechanism of radiation from EBG patterned parallel planes within and outside the bandgap regions. While we acknowledge the importance of understanding the radiation due to the placement of such traces, this study is concerned with interference and radiation caused by switching noise
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