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