Giorgio Gottardi

Codesign of Unconventional Array Architectures and Antenna Elements for 5G Base Stations

An innovative methodological paradigm is proposed for the design of unconventional antenna systems for future 5G base stations. In such a codesign strategy, the antenna element (a spline-shaped patch embedded in a finite-array model) and the overall irregularly clustered-array layout are simultaneously synthesized through a multiobjective antenna-shape optimization combined with a subarraying technique based on a new single-objective integer-coded genetic algorithm able to intrinsically handle constraints on the cluster shapes/types. Selected numerical examples, drawn from an exhaustive design process, are presented to assess the advantages and the effectiveness of the proposed co-design scheme in view of the final manufacturing of 5G base stations thanks to its capability to take into account the impact of mutual coupling, nonideal antenna patterns, and implementation limitations.

Sparse conformal array design for multiple patterns generation through Multi-Task Bayesian Compressive Sensing

The design of a sparse conformal phased array with elements located on a truncated cone shape is addressed. The antenna, supposed to be a fully-digital receiver of an air traffic control system, has to simultaneously generate multiple receiving beams along the elevation plane in order to cover a desired angular region. The synthesis problem is carried out by means of the Multi-Task Bayesian Compressive Sensing (MT-BCS) in order to define the positions of the array elements and the set of complex excitations for each individual beam. A preliminary numerical result is reported to validate the effectiveness of the proposed method.

Performance enhancement of linear active electronically scanned arrays by means of MbD-synthesized metalenses

Abstract The key problem of improving the radiation performances or enabling additive functionalities of linear active electronically scanned arrays (AESAs), without increasing the number of radiating elements nor requiring a re-design of the radiators and/or the feeding network, is addressed by means of a suitably formulated Material-by-Design (MbD) approach. The quasi-conformal transformation optics (QCTO) technique and a customized source inversion (SI) strategy are jointly exploited to synthesize enhanced architectures, composed by a metamaterial lens and a tapered version of the original feeding network, able to match the radiation characteristics of significantly larger and/or different (from the original one) apertures. A set of representative benchmark results is reported to assess the effectiveness of the proposed MbD-designed architecture as well as to highlight the existing trade-off between achievable improvements and the complexity of the arising architectural solution.

Innovative optimization-based design of UWB planar arrays for grating lobes reduction

UWB planar phased arrays with inter-element spacing greater than half-wavelength suffer from the presence of grating lobes in the radiation pattern. An innovative approach to mitigate this problem, based on the optimization of the array elements positions along the broadside direction (z-direction) is presented. The main innovation of the proposed new design methodology is related to the fact that the positions of the array elements are left unchanged in the xy-plane, thus not affecting the planar dimension of the array aperture. Selected numerical results are shown to validate the proposed methodology.

Tiling optimization of orthogonal-polygon shaped aperture for phased array antennas

This work presents an innovative tiling optimization strategy for arbitrary orthogonal-polygon shaped apertures. An exhaustive search approach, together with a multi-objective strategy, has been used in order to obtain optimal tiling configurations, jointly optimizing two different pattern features of interest. A simple example validating the proposed method has been finally reported.

Wideband phased arrays synthesis with maximum bandwidth through iterative convex optimization

This paper presents a novel technique for the synthesis of wideband arrays subject to upper bound constraints on the far field pattern defined through an arbitrarily shaped power pattern mask. A convex programming-based method has been iteratively applied in order to find the optimal excitations satisfying the given radiation requirements over the widest admissible bandwidth. A numerical result is reported for a preliminary assessment of the proposed methodology.

A novel analytic beam steering approach for clustered phased array architectures

The synthesis of the sub-array phases for multi-beams scanning applications is here addressed. A hybrid analog/digital architecture is considered in which analog element excitations are used to generate a reference beam, while a digital sub-arrayed beam-forming network (BFN) is used for steering a secondary beam within a limited scan cone. The digital phases are obtained through an innovative analytic method, jointly optimized with the sub-arrays configuration. A simple numerical assessment has been reported to validate the proposed approach.

Advanced time-modulated array synthesis for directional modulation optimization

The harmonic radiations generated by time-modulated arrays (TMAs) are controlled through the optimization of the on/off behavior of the array elements in order to send the signal undistorted towards desired multiple directions for directional modulation purposes. By using the similarity factor (SF) as an indicator of distortion level, a customized binary Genetic Algorithm (GA) is exploited to optimize the pulse sequence and fit the user constraints defined through a desired SF mask. A preliminary numerical example is included to show the behavior of the proposed method.

Design of notch-enhanced compact printed antennas for 5g communications

The design of a frequency notched antenna for 5G base stations is presented in this paper. In particular, given the considerable number of constraints on the antenna performance, the problem can be defined as a multi-objective problem. The reduction of such complex problem into a single-objective one allows the use of well known optimization strategies like evolutionary algorithms, capable of determine a set of valuable tradeoff solutions. Preliminary numerical results are discussed in order to validate the proposed design procedure.

Innovative array architectures for 5G communications

An innovative iterative scheme which combines parametric optimization techniques and convex programming strategies is proposed as a design tool to assess feasibility and limitations of next generation phased array architectures for 5G backhauling applications. The proposed design technique is aimed at (i) identifying the lattice geometry and minimum array aperture (complying with bandwidth, directivity, and steering range requirements) and (ii) computing the optimal excitation coefficients (to satisfy sidelobe constraints) for a 5G backhauling scenario. Preliminary numerical examples are shown to validate the proposed methodological approach and architectures in 5G backhauling scenarios and to deduce relevant applicative guidelines.