On the Use of Nonlinear Metasurfaces for Circumventing Fundamental Limits of Mantle Cloaking for Antennas

Abstract

The aim of this Communication is to investigate and demonstrate the possibility to overcome the fundamental limitations of mantle cloaking for antennas by exploiting non-linear metasurfaces. First, we recap and give additional physical insights about the fundamental bounds that apply to the electric properties of an antenna that is made invisible at its own resonance frequency. Then, an innovative strategy is proposed to circumvent these limits through the introduction of non-linear elements that are able to dynamically transform the geometry of the cloaking metasurface depending on the power level of the impinging field. Different non-linear designs are discussed, and their effectiveness is assessed through the relevant benchmark example of a half-wavelength dipole antenna able to efficiently transmit high-power signals while being invisible to low power ones. In addition, the capability of such non-linear mantle cloaks to enable the shaping of the radiation pattern of an antenna array depending on the power level of the received/transmitted signal is demonstrated. These innovative cloaking devices may find applications in different radiating systems enabling unprecedented functionalities.

Intelligence Enabled by 2D Metastructures in Antennas and Wireless Propagation Systems

“…As a first example of metasurfaces featuring advanced functionalities [20], we focus our attention on non-linear structures and, in particular, on the possibility to make the behaviour of a metasurface sensitive with respect to the level of the impinging power [21]- [26].…”

“…respectively. The effectiveness of this simple modeleven considering commercial electronic elementshas been checked through a proper full-wave co-simulation routine in [24], while appropriate metasurface geometries for obtaining similar effects for inductive metasurfaces have been described in [26].…”

“…This can be achieved using inductive metasurfaces based on vertical strips and slightly correcting the original geometry to engineer the flow of the currents. More details can be found in [26].…”

“…However, the reduction of the scattering cross section is also accompanied by an important mismatching of the antenna with its source (Fig. 2(b)), as dictated by the optical theorem [26].…”

“…The power threshold at which this transition appears strictly depends on the choice of the non-linear element used to load the metasurface (e.g., for this example, we have considered a Hitachi HVM14S diode and the transition can be observed between 0 and 10 dBm). More details on the co-simulation scheme exploited for performance evaluation can be found in [24], [26].…”