Active Microwave Cloaking Using Parity-Time-Symmetric Satellites

Abstract

In this paper, we present and study the dynamics of an active microwave cloaking technique that alleviates the trade-offs between loss, bandwidth and size, inherent to passive approaches. The presented cloak consists of a finite number of satellite antennas loaded with parity-time symmetric lumped admittances, which, without external control, can track in real-time the amplitude, frequency and phase variations of the impinging signals and generate the required current distributions at the antennas to totally suppress the scattered waves, including reflections and shadows. We analytically derive the optimal density and frequency dispersion of the antenna satellites surrounding the object, in order to achieve substantial reduction in the scattering crosssection over a wide bandwidth. We also investigate the conditions to maintain the cloak stability and study its transient response for excitation with pulsed signals.

Topological Metamaterials

“…EPs are of great interest for various applications. EPs enable unidirectional light transport, leading to the observation of anisotropic transmission resonances, ,,, and directional power flow in microlaser cavities. − The accidental coalescence of eigenmodes offers rich topological features, enabling dynamic chiral-mode conversion, ,, and advanced optical sensing. ,,− scriptP scriptT -symmetric systems hold great promise for imaging, ,− lasing, cloaking and transformation optics, , new mechanisms of wave transport, − topology, light scattering engineering, ,, and wireless power transfer. ,, …”

“…1190−1192 The accidental coalescence of eigenmodes offers rich topological features, enabling dynamic chiral-mode conversion, 1180,1193,1194 and advanced optical sensing. 548,549,1195−1197 -symmetric systems hold great promise for imaging, 705,1198−1202 lasing, 1184 cloaking and transformation optics, 1203,1204 new mechanisms of wave transport, 1205−1207 topology, 1208 light scattering engineering, 543,1209,1210 and wireless power transfer. 1171,1211,1212 -symmetric systems also exhibit various intriguing topological properties.…”

Progress and perspective on advanced cloaking metasurfaces: from invisibility to intelligent antennas

“…For instance, in [107], non-foster devices have been used to broader the cloaking bandwidth. In [108], parity-time cloak with balanced loss and gain have been discussed to cloak electrically large cylinders. Unidirectional mantle cloaks have been proposed to relax some cloaking constraints and, thus, achieve better performances [109].…”

Metamaterials and Metasurfaces—Historical Context, Recent Advances, and Future Directions

“…In the context of active media, a particularly interesting class of metamaterials is the one satisfying parity-time symmetry in the context of non-Hermitian physics, opening the way to a plethora of exotic phenomena of great interest [63]- [67]. Parity-time symmetry requires a balanced distribution of gain and loss in a geometrically asymmetric structure, supporting quite unusual responses, including negative refraction [68], [69] and cloaking [70], [71] without the bandwidth and efficiency limitations of passive metamaterial structures.…”