Numerical homogenization and synthesis of wave polarizers through the Material-by-Design paradigm
A Material-by-Design (MbD) strategy is introduced for the design of multi-layer wave polarizers based on metasurfaces with arbitrarily-shaped unit cells. Following the MbD paradigm, the design is carried by integrating a solution-space exploration block, an electromagnetic simulation block (exploiting a full-wave Method-of-Moments with periodic boundary conditions), a homogenization block, and a cost function evaluation block. Numerical example showing the effectiveness of the proposed strategy is presented.
Generalized QCTO for Metamaterial-Lens-Coated Conformal Arrays
The use of inhomogeneous metamaterial lenses is proposed to enable suitable radiation properties for arbitrary-shape antenna arrays. Towards this end, the Quasi-Conformal Transformation Optics (QCTO) methodology is generalized to allow an arbitrary physical arrangement coated with a suitable lens to exhibit the same radiating features of an arbitrary reference virtual array in free space. A representative numerical example, concerned with a two-dimensional layout, is presented to assess the effectiveness of the proposed method as well as the enhanced features of the resulting metamaterial-coated arrays with respect to standard conformal arrangements.
Design and Implementation of a Closed Cylindrical BFN-Fed Circular Array Antenna for Multiple-Beam Coverage in Azimuth
This paper describes a beamforming network well adapted to produce evenly distributed multiple-beam coverage over a full 360° angular range in azimuth. This structure is very simple, flexible, and compatible with low-cost manufacturing processes such as printed technology. The proposed design is based on balanced power dividers and combiners arranged in such a way to feed a sector of a circular array antenna with Gaussian amplitude distribution and in-phase signals. The first characteristic provides control on the radiation pattern shape, including main lobe shape and sidelobe level, while the second ensures stable beam pointing over a wide frequency range. The proposed azimuth beamforming network is described, and a specific design in microstrip technology is presented with a center frequency at 6 GHz. Simulation results are supported by the measurement of several prototypes. In particular, two designs including the circular array antenna are compared to investigate the impact of the circular array antenna radius on radiation patterns. Despite the assumptions, good correlation is found between simulation and measurement results, thus confirming the properties of the proposed beamforming network concept. Integration of phase controls in the feeding network and its impact on the overall antenna efficiency are also discussed.