Browsing by Author "Wang, Xu Chen"
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Item Graphene-Based Tunable Metasurface for All-Angle Perfect Absorption(2018-11-13) Wang, Xu Chen; Tretyakov, Sergei A.; Department of Electronics and Nanoengineering; Sergei Tretiakov GroupMotivated by the idea of »smart» metasurfaces, we will demonstrate a graphene-based tunable absorber in which perfect absorption can be achieved for all angles of incidence, only by tuning the Fermi level of graphene. We place an unpatterned graphene sheet on a mushroom-type high impedance surface whose resonant frequency is stable for all incident angles. For TM-polarization, perfect absorption can be realized from normal to grazing incidence at the same frequency when modulating the Fermi level of graphene from 0.18 eV to 1 eV.Item Microwave and millimeter-wave characterization of conductive ink film in rectangular waveguide(2017-12-19) Wang, Xu Chen; Díaz-Rubio, Ana; Tretyakov, Sergei; Department of Electronics and Nanoengineering; Sergei Tretiakov GroupAn accurate approach to characterize the sheet impedance of thin conductive ink in rectangular waveguide is reported. This method allows retrieval of the sheet impedance without prior characterization of the supporting dielectric substrate. The ink sample is positioned between two waveguide flanges, introducing a discontinuous gap. The effect of the physical discontinuity can be removed by an additional measurement of the sample without ink layer. We have examined the extraction accuracy of the proposed method within the operating band of the waveguide, and also for various substrate thicknesses. Experimental results demonstrate the applicability of the proposed approach for sheet impedance measurements of ink films on both thin or thick (up to about quarter wavelength) substrates.