High-Frequency Behavior Analysis and Modeling of Degraded Conductive Foams in Signal Return Path

Conductive foams are widely used in the signal return path. Exposure to harsh environments may lead to connection degradation in these foams, which may affect the signal quality of electronic devices. It is of great significance to study the high-frequency electrical and electromagnetic characteristics of degraded foams. In the present work, the impact of such degradation on high-frequency behavior was studied using model analysis and experimental testing. Based on the size and material, the electromagnetic field models of both the circuit board with complete ground conductor and the circuit board with undegraded or degraded conductive foam as part of return path were developed. Using the transmission line theory, the corresponding distributed parameter circuit models for the above three types of circuit boards were also developed. The high-frequency characteristics of degraded conductive foams were evaluated by the $S$ -parameter. The results obtained by model simulations are validated using experimental tests. In addition, the influence of the area between degraded foam and ground conductor on high-frequency characteristics was also investigated from the perspectives of both model simulation and experimental testing. The results of this investigation provide a better understanding of the influence of conductive foam degradation on high-frequency behavior and theoretical support for identifying failure features in fault diagnosis.