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The design of miniaturised linear arrays by using isotropic lenses with reduced complexity is addressed. The problem at hand is formulated as a global optimisation one, then solved by means of a computationally-efficient customisation of the system-by-design (SbD) paradigm suitably integrated with the quasi-conformal transformation optics method. To yield arbitrary transformation geometries with a limited set of degrees-of-freedom and to reduce the lens complexity, while guaranteeing the same radiation performance of a larger reference aperture, a spline-based description of the lens shape is adopted. Representative numerical results are reported to assess the effectiveness as well as the computational efficiency of the proposed SbD-based approach.

Within the transformation electromagnetics (TE) framework, an innovative approach, based on the System-by-Design paradigm, is proposed for the synthesis of isotropic nonmagnetic metamaterial lenses. Selected numerical results, concerned with an application of the SbD-QCTO approach, are reported to give some insights on its advantages and current limitations in terms of computational efficiency, effectiveness, and flexibility.Index Terms-Conformal arrays, metamaterial lenses, metamaterials, quasi-conformal transformation optics (QCTO), system-by-design (SbD).

In this work, we present a procedure to design mantle cloaking devices made of multi-layered metasurfaces. If properly engineered, such covers are able to individually cancel several modes contributing to the scattering from a given object and, differently from traditional mono-layer mantle cloaks, reduce the observability of objects that cannot be considered electrically small. The analytical formulation for cylindrical and spherical geometries is outlined and some examples are provided. Moreover, we propose a potential application of multi-layered mantle cloaks to reduce the blockage effect on antennas due passive supporting structures, without affecting their mechanical characteristics