Ken Morishita

Coupling Analysis of PCB-Chassis Systems with Signal Lines and Via Structures using SPICE

This paper describes the SPICE modeling of printed circuit boards (PCBs) with signal lines and via structures electrically connected to a metal chassis. First, a PCB model is proposed considering the coupling between signal lines and the power bus due to via structures. Next, the model is expanded to include the chassis and grounding posts. The calculated results using SPICE are shown to be consistent with experimental data. Furthermore, positioning of the grounding posts near the edges of the PCB is shown experimentally and numerically to reduce radiated emissions.

Calculation of Optimal Ground Post Resistance for Reducing Emissions from Chassis-Mounted Printed Circuit Boards

When a printed circuit board (PCB) is mounted to a metal chassis, the cavity formed between the circuit board ground and the chassis can resonate at certain frequencies resulting in unintended radiated emissions. The cavity resonances can be effectively suppressed by using conductive mounting posts and adding a resistance in series with the connection between one or more of these mounting posts and the PCB ground plane. This paper derives a simple closed-form expression for determining an optimal series resistance for damping these cavity resonances over a wide range of frequencies. This analysis was done for rectangular boards mounted on four posts located near the corners. A similar analysis could be done to determine the optimal resistance values for other board shapes and mounting post locations. For the four-post configuration, shorting one or more of the posts does not affect the optimum resistance value for the remaining posts.

Modeling Radiated Emissions Due to Power Bus Noise From Circuit Boards With Attached Cables

A two-step technique for modeling the radiation from circuit boards with attached cables is developed and applied to various board-cable structures. The technique divides a complex source geometry into two components. One component consists of differential-mode sources and the pieces of the structure that contribute to the differential-mode radiation. The other component consists of common-mode sources at cable attachment points and the parts of the structure that play a role in the radiation due to common-mode cable currents. The two component geometries are much easier to model than the complete structure. This modeling approach also provides the modeler with insight regarding the design parameters that most influence one type of radiation or the other.

Analysis of EBG structures using SPICE models of multiple planes

Compared to measurements, SPICE models of multiple planes are demonstrated to be effective for analyzing electromagnetic band gap (EBG) structures where unit cells are parallel waveguides coupled to stacked cavities through via posts.