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A phase-only power pattern synthesis technique for flat (aperiodic) microstrip reflectarrays with elements arranged on a non-regular lattice is presented. The approach mitigates the typical design issues of reflectarray antennas related to the computational burden and to the possible occurrence of suboptimal solutions which are here even more significant due to the non-regular element lattice. This is done by a convenient two-stage procedure for choosing the starting point of the iterations and by proper representations of the unknowns of the problem. Design constraints on the element positions are also imposed to avoid overlapping as well as too large spacings. The algorithm, accelerated by parallel programming on Graphics Processing Units, has been analyzed against the cases of a pencil-beam and of a shaped-beam involving a typical South America coverage. In order to properly characterize the performance of the synthesis algorithm, it has been applied also to the design of reflectarrays with elements located on a non-regular lattice. The results show that in the case of non-regular lattice better directivities, better coverage behavior and better side-lobe levels are achievable as compared to reflectarrays characterized by a regular lattice.

A modular technique for the analysis of a dual-reflectarray antenna (DRA) configuration is presented. The proposed analysis method has been used to design a DRA that emulates previous dual-reflector antennas in Ku- and W-bands, including a reflectarray as a sub-reflector. The results for the DRA compare very well with those of the parabolic reflector and reflectarray sub-reflector; radiation patterns, antenna gain and efficiency are practically the same when the main parabolic reflector is substituted by a flat reflectarray, the gain being reduced by a few tenths of a dB as a result of the ohmic losses in the reflectarray. The phase adjustment on two surfaces provided by the dual-reflectarray configuration can be used to improve the antenna performance in some applications requiring multiple beams, beam scanning or shaped beams.

A simple deterministic synthesis method for the design of aperiodic planar arrays with elements arranged on circular or elliptical rings is presented. Differing from other techniques presented in the literature, both the number of elements per ring, as well as the rings' spacing are synthesised, adopting only a deterministic procedure. This permits the best agreement, in terms of least mean square error, with respect to a circularly (or elliptically) symmetric reference pattern.

This paper describes a microwave directional coupler with 3-input and 3-output square-waveguide dual-polarization ports. The proposed 6-port dual-polarization directional coupler is quite attractive as building block of passive beam forming networks, as it allows higher integration with respect to known solutions based on 4-port directional couplers.

The aim of this paper is to propose a novel multibeam antenna feed for reflector based radiating structures. Said feed relies on an overlapped topology, which reduces the distance between active elements and, therefore, the angular separation between beams while maintaining large element aperture and, in this way, high-directivity characteristics. The overlapping is achieved by free-space wave coupling, this eliminating the need for a complex distribution network. By using the proposed design approach, we developed a novel antenna feed featuring well-behaved radiation pattern characteristics with reduced parasitic coupling between adjacent active elements.

A new method for optimising the directional couplers characterising a Skobelev network is presented. The method adopted succeeds in improving the performances of the related sub-array radiation patterns in terms of sidelobe level with negligible effects on the main beam.

The accurate measurement of the permittivity, loss tangent and dielectric anisotropy DC bias dependence for two different liquid crystal (LC) materials in the frequency range 140 GHz-165 GHz is described. The electrical characteristics are obtained by curve fitting computed transmission coefficients to the experimental spectral response of a new class of electronically reconfigurable frequency selective surface. The periodic structure is designed to yield bandpass filter characteristics with and without an applied bias control voltage in order to measure the tunability of the LC material which is inserted in a 705 μm-thick cavity.