Broadband Millimeterwave Metamaterial Absorber Based on Embedding of Dual Resonators

Metamaterial based electromagnetic wave absorbers provide perfect absorption only over a narrow bandwidth.In this paper, broadband response is achieved through embedding of one resonator inside another in each unit cell of the metamaterial absorber lattice.These two resonators are oriented in the same direction to achieve reduced coupling between them realizing two absorption frequencies close to each other in order to broaden the effective bandwidth.The paper presents such an absorber at 77 GHz with a bandwidth of 8 GHz and peak absorption of greater than 98%.The absorber is fabricated on 125 µm thin and flexible polyimide substrate by patterning gold thin film in the shape of two split ring resonators as the metamaterial unit cell.The bandwidth is enhanced by more than a factor of two compared to what could be achieved from a metamaterial with single resonator structure. INTRODUCTIONMetamaterials are made by the inclusion of sub-wavelength metallic structures in host dielectric medium, engineered to achieve unusual properties not found in the nature.Recently, metamaterials has enabled design of thin electromagnetic wave absorbers [1].Absorbers have many applications in radars, imaging [2], wireless communication [3], thermal imagers [4], and possibly in the solar