A Theoretical Investigation of the Resonance Damping Performance of Magnetic Material Coating in Power/Ground Plane Structures

Abstract

Power bus structure, consisting of two parallel solid power and ground planes separated by an insulator, behaves as a cavity resonator at high frequencies. Noise on the power bus, due to a sudden change in the current drawn by an active component, can appear as an undesired spatial fluctuation in the voltage between power and ground, especially at resonant frequencies of the resultant cavity, which may lead to problems in signal integrity, excessive delays, false switching, and radiated emission. These resonances can be suppressed by introducing high-frequency loss into the structure. This paper investigates a simple method to reduce self-/transfer impedance of power/ground planes for mitigating power/ground bounce in high-speed printed circuit board design by adding a thin layer of magnetic material coating to the insidefacing surfaces of copper power and ground plates to increase their effective high-frequency surface impedance. The increased surface impedance will increase the attenuation constant of the propagating wave inside the cavity that benefits reduction of cavity's quality factor (Q factor). The simulation results obtained from a modified cavity resonator model show that increasing surface impedance can dramatically reduce self-and transfer impedances at board resonant frequencies.Index Terms-Cavity resonator model, ground bounce, magnetic material coating, self-/transfer impedance, simultaneous switching noise (SSN), surface impedance.

Resonance suppression and electromagnetic shielding effectiveness improvement of an apertured rectangular cavity by using wall losses

“…Earlier studies have shown that by using lossy materials to absorb the electromagnetic energy in the resonant cavity, the resonance phenomenon could be damped to some degree and the SE near resonant frequencies could be improved. [15][16][17][18] In Ref. [15], it was experimentally verified that the SE near resonance frequencies could be enhanced by placing a layer of lossy dielectric material in the back of an enclosure.…”

“…[15], it was experimentally verified that the SE near resonance frequencies could be enhanced by placing a layer of lossy dielectric material in the back of an enclosure. Reference [16] shows that the resonance noise from a power bus structure can be suppressed by coating the power and ground planes with a thin layer of lossy magnetic material. In Ref.…”