An innovative inverse scattering (IS) technique for the simultaneous processing of multifrequency (MF) ground-penetrating radar (GPR) measurements is proposed. The nonlinear IS problem is solved by ...profitably integrating a customized MF version of the particle swarm optimizer (PSO) within the iterative multiscaling approach (IMSA) to jointly exploit the reduction of the ratio between unknowns and uncorrelated data with a pervasive exploration of the multidimensional search space for minimizing the probability that the solution is trapped into local minima corresponding to false solutions of the problem at hand. Both numerical and experimental test cases are reported to assess the reliability of the MF-IMSA-PSO method toward accurate GPR tomography as well as improvements with respect to the competitive state-of-the-art inversion approaches.
A generalized formulation is derived for the analysis of the field manipulation properties of electromagnetic skins (EMSs) in the working regimes of interest for wireless communications. Based on ...such a theoretical framework, a unified method for the design of anomalous-reflecting and focusing EMSs is presented. Representative results, from a wide set of numerical experiments, are reported and validated with full-wave HFSS simulations to give the interested readers some insights on the accuracy, effectiveness, and computational efficiency of the proposed analysis/synthesis tools.
A novel probabilistic sparsity-promoting method for robust near-field (NF) antenna characterization is proposed. It leverages on the measurements-by-design (MebD) paradigm, and it exploits some a ...priori information on the antenna under test (AUT) to generate an overcomplete representation basis. Accordingly, the problem at hand is reformulated in a compressive sensing (CS) framework as the retrieval of a maximally sparse distribution (with respect to the overcomplete basis) from a reduced set of measured data, and then, it is solved by means of a Bayesian strategy. Representative numerical results are presented to, also comparatively, assess the effectiveness of the proposed approach in reducing the "burden/cost" of the acquisition process and mitigate (possible) truncation errors when dealing with space-constrained probing systems.
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.
A dual-band reflection-mode wide-bandwidth and wide-angle scanning circular polarizer is designed. The proposed polarizer can convert linearly polarized waves into right- and left-hand circularly ...polarized (RHCP and LHCP) waves in the two separate nonadjacent receiving and transmitting K/Ka frequency bands. The polarizer is based on dual-layer dipole arrays printed on both sides of a dielectric substrate separated by a second substrate from the ground plane. An analytic model based on transmission line equivalent circuits is developed. Closed-form expressions are derived to demonstrate the operating principle providing a simple design procedure. The proposed model can be used to optimize the converter for a specific propagation angle of the incident wave. Finally, a system-by-design (SbD) strategy is proposed to improve the performance of analytically synthesized devices. Toward this goal, a computationally efficient "digital twin" of the accurate full-wave model is built to speed up the solution space exploration and efficiently reach the global optimum. A prototype is designed for the incident angle <inline-formula> <tex-math notation="LaTeX">\theta _{0} = 30^{\circ } </tex-math></inline-formula> and it is shown that the axial ratio lower than 3 dB is maintained for a wide-angle field of view of <inline-formula> <tex-math notation="LaTeX">\Delta \theta = 60^{\circ } </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">{\theta }_{min}=0^{\circ },{\theta }_{max}=60^{\circ } </tex-math></inline-formula>) in both frequency bands.
An innovative and computationally efficient compressive sensing (CS) inversion scheme is proposed for the prediction of the 2-D distribution of the electromagnetic (EM) field strength (FS) in a ...region of interest (RoI) starting from a limited set of FS measurements, but without any information on the EM radiating source. Toward this end, the inverse problem at hand is recast to the minimization of the augmented Lagrangian function, and then it is efficiently solved by means of a novel accelerated total-variation CS (ATV-CS) approach. The ATV-CS, which is based on a smart implementation of the involved matrix-vector multiplications, is exploited to remarkably reduce the computational cost of the standard total variation (TV)-CS so that a reliable and efficient prediction of the FS is enabled in realistic applications concerned with wide areas, as well. A set of representative test cases, from a wide numerical assessment concerned with different sources and propagation scenarios, is reported to assess both the reliability/effectiveness and the computational efficiency of the proposed approach in comparison with competitive state-of-the-art sparseness-promoting techniques, as well.
In this paper, a demand-side energy management scheme is proposed to minimize the electricity cost and the peak-to-average ratio. A particle swarm optimization strategy is integrated with a ...game-theoretical approach in order to solve a nonconvex problem of appliance scheduling. The unknowns of the optimization problem are modeled from the user perspective taking in consideration the real-world constraints of appliances, which impose an almost constant power consumption during predefined working time periods and within time windows constrained by the users. The performance of the proposed method has been assessed with different user time constraints. The obtained results outperform a state of the art solution based on convex programming, especially when stringent user requirements are imposed. The peak-to-average ratio is reduced more than twice respect to the convex programming technique.
A novel approach for reliable and effective antenna measurements in cylindrical near-field (NF) setups is presented. Starting from a limited set of NF samples acquired on a finite cylindrical probing ...surface and by exploiting some a priori information on the class of antennas under test (AUTs) to build an overcomplete dictionary of field bases, the proposed method allows one to accurately extrapolate the data well beyond the physical extension of the NF measurement area. Afterward, a compressive sensing (CS)-based method is successfully applied to retrieve a sparse representation of the actual field distribution over the redundant dictionary at hand. Selected results from a wide numerical analysis are shown to assess the effectiveness and the potentialities of the proposed measurement technique.
In this paper, the design of a novel horizontally polarized single‐layer antenna for 77 (GHz) automotive radar applications is4 addressed. An innovative non‐uniform zig‐zag parametrization of the ...antenna layout is considered to enable a more flexible control on both the impedance matching in the working frequency band and the shaping of the radiated beam pattern with respect to a standard (uniform) one without compromising the linear (horizontal) polarization of the radiated field. Such a polarization guarantees a lower back‐scattering from road pavements, resulting in a reduced amount of clutter and thus allowing a more robust target detection. Moreover, the single‐layer layout has several advantages in terms of fabrication simplicity/costs and mechanical robustness to vibrations. The design of the proposed non‐uniform zig‐zag antenna (NZA) is performed through a customized implementation of the System‐by‐Design (SbD) approach that fruitfully combines machine learning and evolutionary optimization to efficiently deal with the computational complexity at hand. An extensive numerical validation, dealing with designs of different lengths, verifies the high performance of the NZA in terms of beam direction deviation (e.g., BDD < 1 (deg)), sidelobe level (e.g., SLL < −18.2 (dB)), and polarization ratio (e.g., PR > 20 (dB)) within the working frequency band B=76:78 $\mathcal{B}=\left76:78\right$ (GHz), as well as its superiority over competitive designs. Finally, the realization of a prototype and its experimental test, validate the proposed NZA concept for automotive mm‐wave radar applications in advanced driver assistance systems and autonomous vehicles such as, for instance, adaptive cruise control, collision avoidance, and blind spot detection.
Key Points
The non‐uniform zig‐zag antenna (NZA) PCB‐based layout enables an effective control of antenna performance for fulfilling a set of conflicting project requirements within automotive radar framework
The proposed SbD‐based optimization method is an effective and efficient tool for addressing the computational complexity of the design problem at hand
The realization and the measurement of a prototype prove also experimentally the suitability of the NZA layout for mm‐wave radar applications
The synthesis of compact metamaterial-loaded sectoral or conical horn antennas matching the radiation properties of larger layouts is addressed. Unlike state-of-the-art strategies, the metamaterial ...lens that fills the miniaturized horn is designed so that the radiated field coincides with that of the reference arrangement both in amplitude and phase. To this end, the synthesis is first recast as a 3-D transformation electromagnetics (TE) problem, then mapped into an equivalent 2-D one. This latter is numerically solved by means of a recently introduced 2-D quasi-conformal TE algorithm. Selected examples from a wide numerical validation and representative comparisons with state-of-the-art methodologies are illustrated.
