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The optimal planning of electromagnetic skins (EMSs) installed on the building facades to enhance the received signal strength, and thus the wireless coverage and/or the Quality-of-Service (QoS) in large-scale urban areas, is addressed. More specifically, a novel instance of the System-by-Design (SbD) paradigm is proposed toward the implementation of a smart electromagnetic environment (SEME) where low-cost passive static reflective skins are deployed to enhance the level of the power received within selected Regions of Interest (RoIs). Thanks to the ad hoc customization of the SbD functional blocks, which includes the exploitation of a digital twin (DT) for the accurate yet fast assessment of the wireless coverage condition, effective solutions are yielded. Numerical results, dealing with real-world test beds, are shown to assess the capabilities, the potentialities, and the current limitations of the proposed EMSs’ planning strategy. [ABSTRACT FROM AUTHOR]

The modular design of planar phased arrays (PAs) arranged on orthogonal polygon-shaped apertures is addressed and a new method is proposed to synthesize domino-tiled arrays fitting multiple, generally conflicting, requirements. Starting from an analytic procedure to check the domino-tileability of the aperture, two multi-objective optimization techniques are derived to efficiently and effectively deal with small and medium/large arrays depending on the values of the bounds for the cardinality of the solution space of the admissible clustered solutions. A set of representative numerical examples is reported to assess the effectiveness of the proposed synthesis approach also through full-wave simulations when considering nonideal models for the radiating elements of the array. [ABSTRACT FROM AUTHOR]

This article presents the complete design of a hybrid metal-plasma transmit-array antenna with beam-scanning capabilities. The antenna operates at 1.07 GHz and consists of an active metallic dipole, a metallic ground plane (GP), and a set of cylindrical plasma discharges arranged in a 2-D lattice. The main lobe of the antenna can be tilted toward different directions simply by turning on/off specific subsets of plasma discharges. Toward this aim, a two-step optimization strategy based on the combination of a particle swarm optimization (PSO) and of a genetic algorithm (GA) is adopted. A realistic model of the antenna has been simulated in CST Microwave Studio. To derive plasma parameters, a prototype plasma discharge has been realized and tested. Each plasma bar included in the numerical setup comprises not only the plasma material, but also the glass envelope and the metallic electrodes used to confine and generate the plasma, respectively. An analysis has been carried out to evaluate the effects of adding the electrically long metallic cables to each discharge needed to ignite and sustain the plasma. The radiation properties of the array can be maintained thanks to the insertion of inductances between the electrodes and the cables. Finally, a sensitivity analysis has been conducted to identify intervals of plasma density and neutral gas pressure within which the beam-scanning capabilities of the antenna remain unaffected. [ABSTRACT FROM AUTHOR]

An innovative method for the design of time-modulated arrays (TMAs) is presented in this letter. The time-domain switching sequence and the parameters of the radio-frequency diodes implementing the time modulation are simultaneously synthesized in order to optimize the features of multiple harmonic beam patterns generated by the TMA. In the proposed codesign strategy, the analysis of the dynamic linear and nonlinear phenomena occurring during a time-based radiation is accurately carried out, including the mutual coupling effects between the radiating elements. A set of representative examples, drawn from an exhaustive numerical validation, is reported and discussed to assess the advantages and the effectiveness of the proposed codesign strategy. [ABSTRACT FROM AUTHOR]

The design of phased arrays able to generate arbitrary-shaped beams through a sub-arrayed architecture is addressed here. The synthesis problem is cast in the excitation matching framework, so as to yield clustered phased arrays providing optimal trade-offs between the complexity of the array architecture (i.e., the minimum number of control points at the sub-array level) and the matching of a reference pattern. A synthesis tool based on the $k$ -means algorithm is proposed for jointly optimizing the sub-array configuration and the complex sub-array coefficients. Selected numerical results, including pencil beams with sidelobe notches and asymmetric lobes as well as shaped main lobes, are reported and discussed to highlight the peculiarities of the proposed approach also in comparison with some extensions to complex excitations of state-of-the-art sub-array design methods. [ABSTRACT FROM AUTHOR]

The design of isophoric phased arrays composed of two-sized square-shaped tiles that fully cover rectangular apertures is dealt with. The number and the positions of the tiles within the array aperture are optimized to fit desired specifications on the power pattern features. Toward this end, starting from the derivation of theoretical conditions for the complete tileability of the aperture, an ad hoc coding of the admissible arrangements, which implies a drastic reduction of the cardinality of the solution space, and their compact representation with a graph are exploited to profitably apply an effective optimizer based on an integer-coded genetic algorithm. A set of representative numerical examples, concerned with state-of-the-art benchmark problems, is reported and discussed to give some insights on the effectiveness of both the proposed tiled architectures and the synthesis strategy. [ABSTRACT FROM AUTHOR]

The modular design of planar phased array antennas with hexagonal apertures is addressed by means of innovative diamond-shaped tiling techniques. Both tiling configuration and subarray coefficients are optimized to fit user-defined power-mask constraints on the radiation pattern. Toward this end, suitable surface-tiling mathematical theorems are customized to the problem at hand to guarantee optimal performance in case of low/medium-size arrays, while the computationally hard tiling of large arrays is yielded thanks to an effective integer-coded GA-based exploration of the arising high-cardinality solution spaces. By considering ideal as well as real array models, a set of representative benchmark problems is dealt with to assess the effectiveness of the proposed architectures and tiling strategies. Moreover, comparisons with alternative tiling architectures are also performed to show to the interested readers the advantages and the potentialities of the diamond subarraying of hexagonal apertures. [ABSTRACT FROM AUTHOR]

A complete framework for the accurate design of time-modulated arrays is presented in this letter. The proper control sequence synthesis originates, for the first time, from the deep knowledge of both the signal level and the switches dynamic, i.e., of the nonlinear regime of these complex radiating systems. The adopted two-nested loop approach relies on the Harmonic-Balance technique and a stochastic algorithm for the accurate estimation of the actual array regime and for an efficient optimization of the time-dependent design parameters, respectively. The effectiveness of the proposed tool is demonstrated through the control of a realistic 16-planar-monopoles array for maximum instantaneous directivity performance. [ABSTRACT FROM AUTHOR]

The problem of designing simplified and cost-effective versions of large phased arrays for a preliminary, but meaningful, experimental testing of a selected set of radiation requisites of the final/complete layouts is addressed. With reference to an array architecture composed by a wide set of equal (or different, even though limited to a finite number of sizes) functional blocks, each one containing the feeding network and the control line for a cluster of elements having independent transmit-receive modules, a novel and ad-hoc method is proposed for determining and selecting the minimum set of blocks of the fully populated array and the excitations of their elements to guarantee the fulfilment of a requested subset of performance of the final/complete arrangement. Representative results are shown and discussed to point out the peculiarities and the potential impact on the active electronically scanned array production cycle of the topic at hand as well as the effectiveness and the potentialities of the proposed design methodology. [ABSTRACT FROM AUTHOR]

The synthesis of time-modulated arrays (TMAs) for physical layer secure communications is carried out in this paper. The problem is cast as the transmission from the TMA of a signal undistorted within a desired angular region, while the signal distortion is maximized elsewhere. Toward this aim, a customized optimization strategy based on a binary genetic algorithm is proposed to define the optimal ON–OFF sequence controlling the radio-frequency switches modulating the signal transmitted by the elements of the TMA. Anad hocfidelity factor metric is used to quantify the signal distortion as a function of the angular direction. A set of numerical examples is reported and discussed to illustrate the behavior of the proposed synthesis approach as well as to give some insights on its potentialities and achievable performance. Moreover, this paper shows, for the first time, the results of an experimental validation when considering a real TMA. [ABSTRACT FROM AUTHOR]

The design of subarrayed planar phased arrays characterized by an irregular organization of domino-shaped tiles is addressed. Starting from optimal tiling theorems drawn from mathematical theory, an enumerative approach able to retrieve the optimal clustering providing the maximum aperture coverage and the best radiation performance is proposed to deal with the synthesis of low-/medium-size rectangular arrays. Based on the same optimal theorems and still exploiting the algorithmic procedures at the basis of the enumerative approach, an innovative schemata-based optimization method is introduced for designing large arrays, as well. A set of representative results, concerned with ideal as well as real radiating elements, is reported and discussed to highlight the features and the potentialities of the proposed analytically based design framework. [ABSTRACT FROM AUTHOR]

The synthesis of frequency diverse arrays (FDAs) able to achieve time-invariant spatial focusing performance in the short-range is addressed. Two time-modulated optimized frequency offset schemes are presented that allow focusing the energy at a single target location and multiple target locations, respectively. A set of numerical examples is reported and discussed to validate the effectiveness of the proposed solutions also in comparison with the already proposed FDA design approaches. [ABSTRACT FROM PUBLISHER]

An inverse method and measurement setup for profile and constitutive parameters reconstruction from monochromatic phaseless information is presented. The method is based on the minimization of a cost function that relates the measured field with the one scattered by a model of the object under test (OUT), where the position, contour, and constitutive parameters are the unknowns. As a result, phaseless information is directly related to the inverse problem unknowns, thus avoiding the need of an intermediate phase retrieval step. Due to the nonlinear nature of the cost function, global optimization techniques, such as the particle swarm optimization and differential evolution algorithms, have been considered for cost function minimization. An exhaustive analysis of the cost function behavior as a function of the electric size of the OUT is presented, discussing the optimal OUT size where the proposed methodology provides accurate profile and constitutive parameters reconstruction. The proposed methodology is conceived to use it together with a simple, low-cost measurement setup for fast characterization of perfect electric conductor and dielectric objects. Measurement examples are presented aiming to prove the feasibility of the described measurement setup. [ABSTRACT FROM PUBLISHER]

A new approach to the power synthesis of fixed-geometry reconfigurable planar arrays radiating sum and difference patterns is presented. The proposed design technique allows to maximize the radiation performance (field slope, amplitude, or even directivity) of both beam patterns over assigned directions subject to completely arbitrary masks for sidelobe bounds. Whatever the elements disposal and the array boundary, the overall problem is solved through a convex (quadratic) programming procedure. Moreover, if centrosymmetric antenna layouts are adopted, the synthesis is reduced to an even more powerful linear programming routine which preserves the solution uniqueness and optimality guaranteed by quadratic programming codes while dramatically decreasing their computational weight (and hence enabling the design of much larger planar arrays). The proposed approach also takes into account the need of reducing the complexity of the beam forming network (BFN), which is fulfilled by sharing part of the excitation amplitudes between the two radiation modalities. A set of numerical examples is reported and discussed to show the versatility and effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]

An approach for the optimal design of linear arrays in the presence of tolerances on the amplitude weights is presented. Starting from the knowledge of the maximum deviations from the nominal values of the amplitude coefficients of the beam-forming network (BFN), an analytical tool based on interval analysis (IA) and integrating a convex programming (CP) method is exploited to maximize the minimum peak value of the main beam of the radiated power pattern along the boresight direction, while fitting an arbitrary user-defined bound on the secondary lobes in a globally optimal fashion. In order to analyze the behavior of the proposed approach also assessing its effectiveness, a set of representative numerical examples regarding arrays of ideal and realistic radiating elements is reported where different sidelobe constraints, array configurations, and tolerance errors are considered. [ABSTRACT FROM PUBLISHER]

Time-modulation (TM) in four-dimensional (4-D) arrays is implemented by using a set of radio-frequency switches in the beam forming network to modulate, by means of periodic pulse sequences, the static excitations and thus control the antenna radiation features. The on–off reconfiguration of the switches, that can be easily implemented via software, unavoidably generates harmonic radiations that can be suitably exploited for multiple channel communication purposes. As a matter of fact, harmonic beams can be synthesized having different spatial distribution and shapes in order to receive signals arriving on the antenna from different directions. Similarly, the capability to generate a field having different frequency and spatial distribution implies that the signal transmitted by time-modulated 4-D arrays is direction-dependent. Accordingly, such a feature is also exploited to implement a secure communication scheme directly at the physical layer. Thanks to the easy software-based reconfigurability, the multiple harmonic beamforming, and the security capability, 4-D arrays can be considered as an enabling technology for future cognitive radio systems. In this paper, these potentialities of time-modulated 4-D arrays are presented and their effectiveness is supported by a set of representative numerical simulation results. [ABSTRACT FROM PUBLISHER]

In this paper, the synthesis of simultaneous multibeams through time-modulated linear arrays is studied. Unlike classical phased arrays where the antenna aperture is usually shared to generate multiple beams, the periodic on-off sequences controlling the static excitations are properly defined by means of an optimization strategy based on the Particle Swarm algorithm to afford desired multiple patterns at harmonic frequencies to make practical application of these harmonic beams which are typically regarded as an undesirable effect in time-modulated arrays. The synthesis of simultaneous broadside sum and difference patterns, flat-top and narrow beam patterns, and steered multibeams is enabled as assessed by a set of selected results reported and discussed to show the potentialities of the proposed method. Comparisons with previously published results are reported, as well. [ABSTRACT FROM PUBLISHER]