Closed-form Harmonic Contrast Control with Surface Impedance Coatings for Conductive Objects

The problem of suppressing the scattering from conductive objects is addressed in terms of harmonic contrast reduction. A unique compact closed-form solution for a surface impedance $Z_s(m,kr)$ is found in a straightforward manner and without any approximation as a function of the harmonic index $m$ (scattering mode to suppress) and of the frequency regime $kr$ (product of wavenumber $k$ and radius $r$ of the cloaked system) at any frequency regime. In the quasi-static limit, mantle cloaking is obtained as a particular case for $kr \ll 1$ and $m=0$. In addition, beyond quasi-static regime, impedance coatings for a selected dominant harmonic wave can be designed with proper dispersive behaviour, resulting in improved reduction levels and harmonic filtering capability.Comment: 6 page

Dual-Circularly Polarized Single-Element Patch Antenna with Compact Multi-Port Feeding

A circularly polarized (CP) S-band patch antenna that makes use of a multi-port setup to improve its radiation efficiency and compactness is presented. The design highlights a single-element patch with eight-port feeding, by using compact slot meandering. To the best knowledge of the authors, no earlier literature discloses a similar single-element patch with eight feeding points made compact by slot meandering whilst demonstrating comparable performances, BW, agility, and polarization purity. In addition, our design utilizes eight, 50- Ω microstrip ports to set and excite the orthogonal polarization states. The miniaturized feeding arrangement, directly under the patch, enables the antenna to produce both left-handed and right-handed CP (as well as other polarization states), making the design suitable for full-duplex and diversity scenarios

Single-Layer Series-Fed Planar Array with Controlled Aperture Distribution for Circularly Polarized Radiation

We propose a compact circularly polarized series-fed patch array with enhanced radiation performance at S -band. To our best knowledge, no similar single-layer structure has been designed, measured, and reported in the literature with equivalent radiation performances in terms of reduced sidelobe level (SLL) and aperture efficiency as well as compactness and simplicity. The planar array consists of a 50- Omega microstrip single feed point, offering uniform and efficient excitation of all its elements that enable a broadside beam with high-gain and low sidelobes. A feeding network for such aperture control is designed and optimized to provide good impedance matching with a two-point excitation per radiating element, which is based on 0° and 90° meander lines to enable circularly polarized radiation. A structure made by a 4!! imes !!1 arrangement of square patches is simulated, optimized, and manufactured, providing a realized gain of about 10 dBic and an SLL below -15 dB. Very good axial ratios and high efficiencies are obtained. The proposed antenna may be of interest for next-generation far-field wireless power transmission systems and other applications including target tracking, radar, and internet of things technologies requiring efficient circularly polarized radiation