Seminar 40, Tuesday 04 May 2021, 14:00 (London Time)
Title: Conceptual-based design of ultra-broadband microwave metamaterial absorber
Speaker: Ping Sheng (Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China)
Abstract: By introducing metallic-ring structural resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged -19.4 dB reflection loss from 3-40 GHz. The overall thickness of the sample is 14.2 mm, only 5% over the minimum thickness dictated by the causality limit. The measured performance is polarization-independent at normal incidence, while absorption at oblique incidence remains considerably effective up to 45 degrees. We provide a conceptual basis for our absorber design, based on the magnetically-excited, two-dimensional capacitive-coupled (electrical) dipolar resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, we use a metallic boundary to split the dipolar resonance into two resonances, and add resistors so as to maximize dissipation over the frequency range in-between the two split resonances. To further extend the absorption spectrum to an ultra-broadband range, we employ a double-layer self-similar structure, in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The resulting microwave absorber pushes the overall performance close to the causality limit, while simultaneously possesses a large relative absorption bandwidth.
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