Abstract
We propose a full optimization procedure for designing mantle cloaks enclosing arbitrary objects, using sub-wavelength conformal frequency selective surface (FSS). Rely on the scattering cancellation principle of mantle cloak characterized by an average surface reactance, a personal computer can achieve this design procedure. By combing a Bayesian optimization (BO) with an electromagnetic solver, we can automatically find the optimal parameters of a conformal mantle cloak which can nearly cancel the scattering from the enclosed objects. It is shown that the results obtained by our method coincide with those from a rigorous analytical model and the numerical results by full parametric scanning. The proposed methodology opens up a new route for realizing ultra-wideband illusion scattering of electromagnetic wave, which is important for stealth and microwave applications.
Highlights
A different cloaking method named scattering cancellation technique[17,18,19,20,21,22] has been proposed to overcome these issues
Supposed the size of the frequency selective surface (FSS) elements is far less than the operating wavelength, the FSS can be effectively described with an equivalent surface impendence Zs = Rs − iXs, where Rs is the surface resistance associated with losses and Xs relates to the stored energy, which can be either inductive or capacitive, depending on the FSS structure
For an infinite long cylinder or a sphere with mantle cloaks, the scattering coefficients can be analytically calculated by forcing a discontinuity of the tangential magnetic field on the surface of the cloak, and they are functions of the frequency, Xs of the cloak, the thickness and dielectric constant of the material filled between the cloak and the object[19,20,21,22]
Summary
A different cloaking method named scattering cancellation technique[17,18,19,20,21,22] has been proposed to overcome these issues. Other issues such as fabrication requirement of the devices, attrition rate of the material should be taken into account Considering all these factors, direct parametric scanning in simulations is inadvisable and some sophisticated but efficient optimization algorithms are highly demanding[26,27]. From simplistic procedures like grid or random search[28,29,30], to more sophisticated model-based approaches using random forests[31] or Gaussian process (GP)[32] Among these optimization algorithms, Bayesian optimization (BO) is a well recognized algorithm for solving global optimization problems with non-convex black-box function[33,34,35,36,37,38]. We further demonstrate that the proposed method can successfully design mantle cloaks based on metasurface for other two- (2D) and three-dimensional (3D) geometries that are impossible to be theoretically analyzed
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