In this letter, we investigate the possibility of using the mantle cloaking approach to reduce mutual blockage effects between two electrically close antennas. In particular, we consider the case of two dipoles resonating at different, close frequencies and separated by an electrically short distance ( λ ₀ /10 at 3 GHz). We show that by covering the two antennas with properly patterned metasurfaces printed on realistic substrates, it is possible to make each antenna invisible to the other and preserve their individual operation as if they were isolated. This new cloaking application is confirmed by realistic full-wave numerical simulations.

So far, the environment has been considered as a source of fading, clutter, blockage, etc., with detrimental consequences for the efficiency and robustness of communication systems. However, the intense research developed toward beyond-5G communications is leading to a paradigm change, in which the environment is exploited as a new degree of freedom and plays an active role in achieving unprecedented system performances. For implementing this challenging paradigm, it has been recently proposed the use of intelligent surfaces able to control almost at will the propagation of electromagnetic waves. In this framework, metasurfaces have emerged as a promising solution, thanks to their field manipulation capabilities achieved through low-cost, lightweight, and planar structures. The aim of this paper is to review some recent applications of metasurfaces and cast them in the scenario of next-generation wireless systems. In particular, we show their potentialities in overcoming some detrimental effects presented by the environment in wireless communications, and discuss their crucial role towards the practical implementation of a smart electromagnetic environment.

We present the design and realization of anisotropic mantle cloaks operating, at the same frequency, for both TM and TE incident polarizations. Starting from the analytical model of metasurfaces available in the literature, we first explore the potentials and limitations of the most common metasurface geometries for their application as mantle cloaks. Then, we introduce new types of patterned surfaces aimed at improving their polarization response. We demonstrate that, only by using four metasurface topologies, it is possible to obtain all required combinations of positive and negative reactance values in order to design effective mantle cloaks for planar, cylindrical, and three-dimensional (3-D) objects. We also show that the accuracy of the analytical formulas commonly used to design such metasurfaces is not necessarily sufficient for cloaking purposes. Therefore, we introduce and validate a numerical procedure to refine the analytical design and optimize the cloak performance. The effectiveness of the designed covers is checked with full-wave simulations. Finally, some antenna applications of dual-polarized mantle cloaks are proposed and several experimental measurements conducted on fabricated prototypes are also provided.

We show that properly designed mantle cloaks, consisting of patterned metallic sheets placed around cylindrical monopoles, allow tightly packing the same antennas together in a highly dense telecommunication platform. Our experimental demonstration is applied to the relevant example of two cylindrical monopole radiators operating for 3G and 4G mobile communications. The two antennas are placed in close proximity, separated by 1/10 of the shorter operational wavelength, and, after cloaking, are shown to remarkably operate as if isolated in free-space. This result paves the way to unprecedented co-siting strategies for multiple antennas handling different services and installed in overcrowded platforms, such as communication towers, satellite payloads, aircrafts, or ship trees. More broadly, this work presents a significant application of cloaking technology to improve the efficiency of modern communication systems.

We theoretically and experimentally explore the use of mantle covers to cloak dipole antennas and reduce their blockage on nearby antennas. The proposed structures allow reducing the observability in a given frequency range and overall scattering of conventional dipole antennas operating in a different frequency band, ideally suited to reduce the mutual influence among antennas placed in close proximity to each other. We prove this concept in the case of a low-band (LB) dipole antenna placed in close proximity to a high-band dipole antenna, and study several thin cover designs that are shown to be effective in reducing the LB blockage, without disrupting the performance of both antennas in terms of radiation pattern and impedance matching. An optimized cover is proposed to strongly reduce the interference and shadowing over a large bandwidth targeted for one polarization, and we also experimentally demonstrate the operation of dual-polarized covers for near-field horn and log-periodic antenna excitation.