Design and Validation of Single-Layer Evanescent Wave Absorber in Rectangular Waveguide

In this work, for absorbing waves below the cutoff frequency of a rectangular waveguide (RWG), i.e., absorb the evanescent waves (EWs), a single-layer EW absorber with an ideal lossy capacitive metasurface (LCMS) is proposed. Based on the principle of momentum matching, the working mechanism is analyzed. Prototype is fabricated for validation, and the maximum measured absorptance reaches 97%. The EW absorber provide a new approach to reduce electromagnetic interference (EMI) caused by the evanescent modes in small metallic cavities and near-field of integrated circuits (ICs).