A monolithic numerical model to predict the EMI shielding performance of lossy dielectric polymer nanocomposite shields in a rectangular waveguide: Design of an absorption-based sawtooth-shaped layer

A three-dimensional numerical model is constructed to predict the EMI shielding performance of a polymer nanocomposite shield in a rectangular waveguide. The Helmholtz wave equation for the electric field is implemented in component form and the set of coupled equations is solved via the finite element approach. Mesh convergence and model verification is performed by comparing free space model predictions for a flat, uniform layer to benchmark solutions calculated via transfer matrix theory. The capability of the model is showcased by exploring the role of geometry on the shielding performance of a sawtooth-shaped composite layer in a rectangular waveguide. Increasing the inclusion angle of the sawtooth, which is proportional to the ratio of the sawtooth amplitude and repeat unit width, reduces the transmitted power through the shield and increases the ratio of absorption to reflection of wave power by the shield. Thus, a rational design of this sawtooth geometry allows to overcome the typical trade-off between total shielding effectiveness and wave absorption contribution, thereby resulting in highly performant absorption-dominated shields.