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The evolution in wireless radio communication systems has fueled the development of array antenna designs toward the direction of inventive, economical, and outcome-driven solutions. This article explored unorthodox techniques for designing array antennas for multiple radiation pattern synthesis by eradicating the required attenuators and phase shifters. An economical alternate design model is proposed with "Time-modulated" antennas capable of scanning and steering the beam electronically. "Time" is employed as a four-dimensional antenna parameter, and hence, the "Time-modulated" antennas are referred to as four-dimensional (4D) antennas. The idea is conceptualized by controlling high-speed switches attached to the antennas in a periodic way to produce the desirable excitation and phase tapering. So, the requirement of costly phase shifters and attenuators is eliminated. This work expanded the idea of "Time-modulation" for synthesizing multiple radiating beams such as monopulse, scanned beams, and shaped beams for multifunction radar systems. An appropriate switch sequence is designed to produce a concurrent sum-difference pattern for monopulse radars. Simultaneous scanning patterns and shaped flat-top patterns are also proposed for multifunction radars. To achieve the goals, two sets of 4D linear arrays are designed and the modulation parameters switch ON time and periods are optimized with a quasi-Newton memetic GA (Genetic algorithm). All the optimal outcomes are reported and also compared with other counterpart outcomes to show the efficacies of the "Time-modulation" concept for the said applications. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-coverage Electromagnetic Skin (EM skin) based on a single-layer reflecting panel to provide coverage of blind zones and enhance 6G communications at sub-THz frequencies. The proposed EM skin is able to generate two independent reflected beams in orthogonal linear polarizations, which are pointed in different fixed directions to cover two different regions of users. The unit-cell of the EM skin is based on orthogonal groups of dipole-type elements, which provide independent phasing capability in each linear polarization. A beamforming technique has been applied to broaden the beams in the elevation and azimuth planes with respect to the reference pencil-beam design, so as to cover a wider angular region of $10^{\circ } \times 10^{\circ } $ . A 68 mm $\times 68$ mm EM-skin prototype, comprising $40\times 40$ reflecting cells, has been fabricated and tested, showing good agreement with the simulations at the design frequency of 100 GHz, low cross-polar levels, and stable gain and beamwidth performance in the 95-104 GHz band. The proposed EM skin is a low-cost and energy-efficient solution for improving wireless coverage of blind zones in sub-THz 6G systems, in those scenarios where there is no direct line of sight with the base station or hotspot.

This paper provides new designs and realizations of leaky-wave (LW) metasurface (MTS) antennas fed at multiple points. The design technique is based on the direct integral-equation solution by the Method of Moments (MoM). The unknown is no longer the current distribution, but the impedance profile itself. The method can be used to generate any shaped radiation pattern in amplitude, phase, and polarization, provided that the antenna area and the feeder illumination are consistent with the shape of the desired radiation pattern. The algorithm can also be used to design multi-functional antennas (multibeam, multiband, dual-polarizion, etc). While multiple feeds are traditionally used to implement multiple fonctionnalities, they may also be required for the efficient generation of a single shaped beam, thus leading to a higher surface-wave (SW) to LW conversion efficiency. The present paper shows for the first time, two realizations of MTS design with the integral equation formalism, which require the usage of multiple feeds: a circularly polarized sectoral conical beam and a dual-polarized broadside beam MTS antenna. The good comparison between measurements and numerical predictions shows the effectiveness of the design method.

We propose a new approach to the mask-constrained synthesis of shaped beams through generic array antennas having arbitrary layouts and element patterns. The introduced general methodology allows casting the design problem as a finite number of Convex Programming optimizations and can generate different excitation solutions all fulfilling the required specifications. Numerical examples, including planar arrays and the full-wave synthesis of an aperiodic array, are provided in support of the given theory. [ABSTRACT FROM AUTHOR]

With reference to the mask-constrained power synthesis of shaped beams, we extend the spectral factorization method to both uniformly and nonuniformly spaced linear arrays wherein mutual coupling and mounting-platform effects are present. The overall design procedure does not rely on any restriction on the nature and the shape of the fields, and it is cast as a couple of convex optimizations plus a polynomial factorization. Moreover, it allows one to ascertain the actual feasibility of the radiating system before performing the synthesis, and it is able to identify very many different array-excitation solutions all corresponding to the desired power pattern. The given theory is supported by numerical experiments concerning the full-wave synthesis of realistic arrays affected by mutual coupling and mounting-platform effects. [ABSTRACT FROM AUTHOR]

A novel hybrid approach to the power synthesis of mask-constrained shaped beams by means of concentric-ring isophoric arrays is presented. The basis of this procedure is to use the complex aperture distribution obtained by Elliott–Stern method as a starting point of an innovative algorithm that combines a classical density tapering method with a simulated annealing one. The proposed technique allows to outperform the previous procedures. [ABSTRACT FROM AUTHOR]

In this paper, a synthesis method for a shaped-beam pattern of the 2-D array antenna is proposed. The method is based on the array scanning principle and the superposition principle. The method can limit the ripple of the main beam by adjusting the sampling point interval and can easily achieve low sidelobe level (SLL). Compared to the stochastic optimization methods, this method has obvious time advantage when it is used to synthesize a large array antenna. The factors that affect the SLL, ripple, and dynamic range ratio (DRR) are discussed. Sparse array is used to reduce DRR. [ABSTRACT FROM AUTHOR]

A technique for the synthesis of shaped beam radiation patterns is proposed. The new synthesis method is based on superposition principle and Taylor method. The method may control the sidelobe level of the shaped beam. The approach includes four steps: 1) get the distribution of pencil beam array with low sidelobe by Taylor method; 2) let the beams scan as a phased array to the specific angles according to the requirement of the shaped beam, The sum pattern is close to the shaping beam; 3) determine the value of angles and weights; and 4) count the distribution of the shaped beam array according to the new array factor function. Numerical results are provided to assess the capabilities of the proposed design method. The method develops an effective approach for the synthesis of shaped beams via uniform linear arrays. Both the ripple and sidelobe level of shaped beam may be controlled by the new synthesis method. [ABSTRACT FROM AUTHOR]

We propose a new deterministic approach to the synthesis of linear arrays having the least possible number of elements while radiating shaped beams lying in completelyarbitrarypower masks. The approach takes joint advantage from compressive sensing (CS), from the multiplicity ofpowerpatterns lying in a given mask, and from the multiplicity offieldsolutions corresponding to each of these power patterns. Care is taken in order to exploit the available degrees of freedom in an effective fashion, and in optimizing parameters that affect the CS performance. An extensive numerical comparison against state-of-the-art procedures proves the effectiveness of the approach. [ABSTRACT FROM PUBLISHER]

We present a novel algorithm for the synthesis of planar (2-D) arrays subject to arbitrary pattern masks and excitation constraints (e.g., dynamic range). The algorithm is simple and deterministic, and considers the radiating element pattern. The procedure starts with a conventional constrained fixed-grid synthesis on a regular lattice, yielding a goal radiated field. Next, element locations are selected sequentially by maximizing projection on field difference to goal, while excitation amplitudes are computed using fixed-grid constrained synthesis for irregular lattices. The final result is the sparse layout and constrained excitation coefficients. The proposed method is validated against literature results; application examples are given for circular flat-top, isoflux and triangular flat-top shaped beam patterns, with constraints on excitation coefficients dynamic range, both for isotropic and patch-type element patterns. [ABSTRACT FROM PUBLISHER]

Abstract: We present a semi-analytic theory for calculating light–particle interactions in shaped laser beams even when the paraxial beam description is invalid. It requires weighting the expressions for the cross sections with a beam normalization parameter, , associated with the incident power. An analytical formula for in terms of the beam shape coefficients [1–3] is derived. We show that approximate expressions for this beam normalization parameter based on either a Parseval or paraxial type approximation are inadequate for optics involving high numerical apertures. [Copyright &y& Elsevier]

A rigorous deterministic approach is proposed for the mask-constrained power pattern synthesis of shaped beams through one-dimensional sparse arrays having uniform-amplitude excitations (and variable phases). The approach includes the well known density taper procedure as a special case. The corresponding technique, which exploits an analytical formulation of the problem and convex programming routines, results in fast computation and is able to achieve optimal solutions without recurring to any global optimization. Numerical results assessing the capabilities of the proposed design method are provided, opening the way to the development of an effective approach for the synthesis of circularly symmetric shaped beams via uniformly-excited circular ring arrays. [ABSTRACT FROM PUBLISHER]

We investigate the radiation capabilities of focal array fed dielectric lens antennas using the FDTD method. Several relevant configurations sharing the same lens architecture (namely an extended hemispherical lens coated with a quarter wavelength matching layer), but illuminated by different sub-array topologies, are compared. In particular, we study the impact of the feeding amplitude coefficients, sub-array size and location upon the radiation patterns and beam scanning performance of the lens. Our numerical results demonstrate that such lens configurations are very attractive and flexible for beam synthesis at millimeter waves (beam shaping, beam scanning and beam reconfiguration). These conclusions are confirmed successfully by several experimental results in Ka-band obtained with a 8 × λ0 lens in Rexolite illuminated by linear printed antenna arrays of variable size. [ABSTRACT FROM PUBLISHER]

A new approach to the optimal synthesis of planar arrays able to radiate mask-constrained shaped beams by exploiting the minimum number of radiating elements is presented. By taking advantage from both the recent theory of Compressive Sensing and the multiplicity of equivalent solutions available for the generation of an unique shaped-beam power pattern, the synthesis results extremely fast and effective. In particular, the overall design is reduced to a Convex Programming optimization, with the inherent advantages in terms of solutions' optimality and computational burden. [ABSTRACT FROM AUTHOR]