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A planar electromagnetic bandgap configuration of a compact common mode filter that is laid out on printed circuit board is studied. This filter is used to mitigate the common mode noise traveling on high-speed differential signal traces. These differential signal lines may be connected to I/O connectors and cables and small amounts of common mode noise can result in significant electromagnetic emissions. The filter is obtained by a very simple planar geometry based on the electromagnetic bandgap structures. A cavity made by a rectangular/square patch (together with a solid plane underneath) has a well known and predictable resonant behavior; the coupling between the differential pair routed on top of the patterned plane and the patch cavity, occurring when the traces cross the gap between adjacent patches, is used to reduce the energy associated with the propagation of the common mode noise. The properties of this filter are studied taking into account the layout of a real differential microstrip and the number of gap crossings. A compact configuration is proposed. Time domain simulations validate the suggested layout approach.

In this paper, a simple synthesis procedure to design planar electromagnetic bandgap (EBG) structures is proposed. It is based on the consideration of the excess of inductance of a patterned plane with respect to a solid one. The planar EBG structure is sized from the bandgap starting and ending frequencies, and few others specifications employing a closed form formulation. The proposed method is also suitable for the design of embedded planar EBG. The procedure is validated by using measured and numerically computed results.

In this paper, an embedded electromagnetic bandgap structure is proposed for harmonic filtering of differential signal's undesired common mode components. Rather than use lumped circuit components and likely causing some degradation to the intended high speed differential signal, the embedded planar common mode filter causes no degradation to the intended signal, and enhances the signal integrity and electromagnetic compatibility performance of the system. Single ended and differential traces are considered and the impact of the common mode filtering is measured in terms of mixed mode scattering parameters and eye diagram metrics. The systematic procedure to design such a structure is outlined, and its design robustness is also verified.

This paper investigates the power integrity behavior of planar electromagnetic bandgap (EBG) structures embedded between two solid layers within the stack-up of a multilayer printed circuit board. The bandgap generation and power integrity performance of the embedded EBG can be achieved only by placing vias shorting the solid planes above and below the patterned layer. The vias inhibit the resonances of the cavity made by the two solid planes, ensuring the designed bandgap, as if the planar EBG was laid out on an outer stack-up layer. The impact of the stitching vias' number and location is addressed and the concepts of regular, global, random, or local via placement are introduced.