Abstract-In this paper a compact antipodal Vivaldi antenna with dimensions of 40 × 85 mm 2 for Ka band is presented. To enhance the antenna gain epsilon near zero metamaterial (ENZ) unit cells are embedded at the same plane of the Vivaldi flare aperture. These ENZ unit cells have the advantage of confining the radiated fields with additional compact size. The obtained antenna exhibits an ultra-wide bandwidth from 23 GHz to 40 GHz with a reflection coefficient less than −10 dB. This is suitable for 5G applications at both 28 and 38 GHz. The antenna gain in this frequency band is found in the range from 14 to 17.2 dBi. The proposed antenna is designed by using CST-MW Studio, and the results are verified with experimental measurements.

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Cloaking refers to hiding a body from detection by surrounding it with a coating consisting of an unusual anisotropic nonhomogeneous material. The radially-dependent spherical cloaking shell can be approximately discretized into many homogeneous anisotropic layers, provided that the thickness of each layer is much less than the wavelength, and this discretization raises the level of scattering as the number of layers decreases. Each anisotropic layer can be replaced by a pair of equivalent isotropic sub-layers, where the effective medium approximation is used to find the parameters of these two equivalent sub-layers. In this work, the scattering properties of cloaked perfectly conducting sphere is investigated using a combination of approximate cloaking, where the conducting sphere is transformed into a small sphere rather than to a point, together with discretizing the cloaking material using pairs of homogeneous isotropic sub-layers. The back-scattering normalized radar cross section, the scattering pattern are studied and the total scattering cross section against the frequency for different number of layers and transformed cloaking radius.

In this paper, we develop a multi-band circularly polarized planar antenna operating at 28 GHz and 60 GHz for 5G and WiGig applications. The antenna is composed of a square slot antenna fed by a proximity coupled microstrip line and loaded by grounded square loop and three tilted angle strips. Grounded square patch introduces resonance at 60 GHz frequency while the strips introduce resonances at 28 GHz. The square slot is designed as a wide-band antenna which can support these two resonances.