Broadband Antireflective Properties of Inverse Motheye Surfaces

A new method for synthesizing broadband antireflective (AR) surfaces at microwave and millimeter wave frequencies is demonstrated. The AR surface, we call an inverse motheye, was formed by machining a multi-layer grating of subwavelength circular holes into a non-absorptive dielectric. This created low reflected energies (<; - 30 dB) over reasonably large bandwidths and incidence angles. An optimization algorithm, based on a direct pattern search, integrated with a rigorous electromagnetic model was used to design the grating geometries. Experimental results are provided at Ka-band demonstrating the validity of the method.