Active Microwave Cloaking Using Parity-Time-Symmetric Satellites

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 in 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 necessary to maintain the cloak stability and study its transient response for excitation with pulsed signals.