Browsing by Subject "Multi frequency"

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    Decoupling of multifrequency dipole antenna arrays for microwave imaging applications
    (Hindawi Publishing Corporation, 2010) Saenz, E.; Guven, K.; Özbay, Ekmel; Ederra, I.; Gonzalo, R.
    The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S -parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.
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    Non-ideal cloaking based on Fabry-Perot resonances in single-layer high-index dielectric shells
    (Optical Society of American (OSA), 2009) Serebryannikov, A.E.; Usik P.V.; Özbay, Ekmel
    Strong reduction of the scattering cross section is obtained for subwavelength dielectric and conducting cylinders without any magnetism for both TE and TM polarizations. The suggested approach is based on the use of Fabry-Perot type radial resonances, which can appear in single-layer, high-ε, isotropic, and homogeneous shells with the properly chosen parameters. Frequencies of the minima of the scattering cross section, which are associated with the cloaking, typically depend on whether TE or TM polarization is considered. In some cases, large-positive-ε and largenegative-e objects can be cloaked. In other cases, non-ideal multifrequency cloaking can be realized. ©2009 Optical Society of America.