Optically Transparent Ka‐Band Absorber With Multi‐Fractal Rings and a Metal Mesh Ground Plane

An optically transparent absorber based on multi‐fractal ring resonators and a metal mesh ground plane is presented for Ka‐band applications. By merging multiple resonances, the proposed absorber maintains an absorption bandwidth from 25.8 to 31.1 GHz. The metal mesh ground plane provides 89% optical transparency while exhibiting only a 0.11‐dB difference in the referenced reflection loss compared to a continuous metal ground at 28.0 GHz. Measured results confirm good agreement with simulations and demonstrate angularly stable absorption under oblique incidence. This proposed structure can be integrated onto glass surfaces to suppress window‐induced reflections in dense millimeter‐wave propagation environments.