Waveguide Tubes Coated With Inhomogeneous Lossy Materials for Superior Shielding Above and Below Cutoff Frequency

A new approach for enhanced electromagnetic interference shielding of metallic waveguide (WG) tubes coated with inhomogeneous lossy materials is proposed based on numerical simulation. Shielding enhancement is achieved by using stepped variations of complex permittivity and complex permeability coating materials along the WG transverse direction. Such variation in the coating layer provides multiple wave reflections below and above the WG cutoff frequency. The underlying principle is applied to a rectangular WG operating in the dominant TE₁₀ mode. Simulation examples of rectangular WGs coated with uniform and stepped lossy materials are demonstrated. The proposed approach shows remarkably better performance when compared with WGs coated with uniform lossy materials.