An investigation of the effect of chassis connections on radiated EMI from PCBs

Abstract

Abstract-This paper investigates the effect of grounding posts when printed circuit boards are mounted near and parallel to a metal plate or chassis. Specifically, experimental data showing changes in radiated emission levels are explained by means of coupling phenomena between a power bus, a chassis cavity including grounding posts, and a cable connected to the power bus. This coupling is modeled using SPICE and the results are combined with an equivalent magnetic current source model to estimate the radiated emissions from various printed circuit board configurations. The calculated results are shown to be consistent with the corresponding experimental data.

Analysis of a PCB-chassis system including different sizes of multiple planes based on SPICE

“…via structures in a PCB or grounding posts connecting a PCB to a metal chassis) were proposed to investigate coupling inside a PCB or radiated emissions from PCB-chassis systems [1][2] [3]. Although the calculated results from these models were shown to be consistent with the corresponding experimental data, these models only handle multiple plane structures where the sizes of the inner layer planes are the same as the outer layer planes.…”

“…Procedures for modeling multiple planes with vertical connecting conductors (vias or grounding posts) are introduced in [1][2] [3]. These procedures are based on a radial/coaxial line junction model [7].…”

“…the power bus in a PCB or the space between a PCB and metal chassis) [1]. Injected noise may resonate in the cavity or couple to neighboring cavities resulting in radiated emissions.…”