Array Excitation Research Articles

Optimization of Multibeam Antennas Employing Generalized Joined Coupler Matrix

Currently, there is increasing interest in analog multibeam antennas whose beams can be flexibly steered to arbitrary directions. In a previous paper, we presented the theoretical framework for synthesizing individually steerable multiple beams using generalized joined coupler (GJC) matrices. The synthesis method was to optimize the array excitation vectors to approximate known distributions. In this article, we present a more robust optimization method to optimize the multibeams directly in order to control the half-power beamwidth, the sidelobe levels, and nulls for mitigating system interference. The effectiveness of the proposed method is demonstrated by numerical examples. We reveal how the quality of the multiple beams is inherently determined by the dimensions of the GJC matrix. Experimental results of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\,\, \times10$ </tex-math></inline-formula> Nolen-like GJC matrix are presented for the first time to validate the proposed method in realizing low sidelobe multibeams.

Quantum-Inspired Equilibrium Optimizer for Linear Antenna Array

With the rapid development of communication technology, the problem of antenna array optimization plays a crucial role. Among many types of antennas, line antenna arrays (LAA) are the most commonly applied, but the side lobe level (SLL) reduction is still a challenging problem. In the radiation process of the linear antenna array, the high side lobe level will interfere with the intensity of the antenna target radiation direction. Many conventional methods are ineffective in obtaining the maximum side lobe level in synthesis, and this paper proposed a quantum equilibrium optimizer (QEO) algorithm for line antenna arrays. Firstly, the linear antenna array model consists of an array element arrangement. Array factor (AF) can be expressed as the combination of array excitation amplitude and position in array space. Then, inspired by the powerful computing power of quantum computing, an improved quantum equilibrium optimizer combining quantum coding and quantum rotation gate strategy is proposed. Finally, the proposed quantum equilibrium optimizer is used to optimize the excitation amplitude of the array elements in the linear antenna array model by numerical simulation to minimize the interference of the side lobe level to the main lobe radiation. Six different metaheuristic algorithms are used to optimize the excitation amplitude in three different arrays of line antenna arrays, the experimental results indicated that the quantum equilibrium optimizer is more advantageous in obtaining the maximum side lobe level reduction. Compared with other metaheuristic optimization algorithms, the quantum equilibrium optimizer has advantages in terms of convergence speed and accuracy.

Single-mode Lamb wave excitation at high-frequency-thickness products using a conventional linear array transducer

Lamb wave excitation at high-frequency-thickness products offers a potential solution for high-resolution guided wave testing. The method is attractive for crack imaging and corrosion mapping, especially in hidden locations where direct access is limited. However, multiple modes may propagate, complicating signal interpretation, which is undesirable. In this work, a systematic approach is presented, in an effort to determine the influence of the key parameters related to single higher order Lamb wave mode excitation using a conventional linear array transducer. Specifically, a linear time delay law is used to enhance the targeted mode, while the array's length, pitch and apodisation profile remain to be optimally selected. First, an analytical solution is derived based on modal analysis. This provides a natural decomposition of the amplitude of a guided wave mode into the product of the response of a single element and the excitation spectrum. Then, a key observation is made, associating the excitation spectrum to the directivity function for bulk wave phased array steering. This allows the application of well-established phased array analysis tools to guided wave phased array excitation. In light of this fact, minimisation of the spectrum’s bandwidth, elimination of the grating lobes and derivation of an apodisation profile are performed, to enhance the purity of the targeted mode. Finally, experiments conducted on an aluminium plate verify the above theoretical results. The Full Matrix is acquired, and all signals are reconstructed synthetically.

Efficient Radiation Pattern Prediction of Array Antennas Based on Complex-Valued Graph Neural Networks

Antenna design with the traditional numerical methods is a highly computationally expensive task. In this letter, a complex-valued graph neural network (GNN) with residual connections is proposed to efficiently predict radiation pattern for antenna arrays with different geometric structures. The model uses GNN as a backbone, and the topological structure and excitation of the antenna array are encoded into a graph representation. Complex weights and residual connections are designed to improve the accuracy of the model. Experiments are conducted on five kinds of arrays under amplitude–phase control. The experimental results show that the average mean absolute percentage error and the average root-mean-square error of the model on five types of the antenna array are 1.86% and 0.032, respectively, while the time efficiency of the model is six orders of magnitude faster than that of the traditional full-wave simulation.

Irregular Phased Array Architecture With Small Directivity Drop for Wide-Angle Scanning Application

A novel irregular phased array tiled by subarrays composed of two isolated elements (SCTIEs) is proposed in this article. At first, reasons of significant directivity drop in traditional polyomino-shaped irregular arrays in large-angle scanning scenario are investigated. To reduce the quantization errors of the excitations, the two elements in this proposed irregular array are interleaved with one element which belongs to another subarray. Second, to solve the complex double-element irregular subarray tiling problem, a new approach named Subarray Rotation Algorithm based on Monte Carlo algorithm is proposed. Since the problem is no longer regarded as a nonlinear pure integer programming problem as that in previous research but a simplified element-location transformation problem, the proposed method can dramatically reduce the optimization time to 0.07% for an array as large-scale as 36 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times36$ </tex-math></inline-formula> . Consequently, through the two steps of array tiling generation and excitation coefficients optimization, better radiation performance is realized based on the SCTIE-shaped irregular arrays compared with conventional domino-shaped arrays. In addition, the proposed irregular array achieves stable performance in a broad frequency band and in different array scales. Finally, several numerical examples are presented to verify the proposed method.

Hybrid discrete-continuous truncated Wigner approximation for driven, dissipative spin systems

We present a systematic approach for the semiclassical treatment of many-body dynamics of interacting, open spin systems. Our approach overcomes some of the shortcomings of the recently developed discrete truncated Wigner approximation (DTWA) based on Monte-Carlo sampling in a discrete phase space that improves the classical treatment by accounting for lowest-order quantum fluctuations. We provide a rigorous derivation of the DTWA by embedding it in a continuous phase space, thereby introducing a hybrid discrete-continuous truncated Wigner approximation (DCTWA). We derive a set of operator-differential mappings that yield an exact equation of motion (EOM) for the continuous SU(2) Wigner function of spins. The standard DTWA is then recovered by a systematic neglection of specific terms in this exact EOM. The hybrid approach permits us to determine the validity conditions and to gain detailed understanding of the quality of the approximation, paving the way for systematic improvements. Furthermore, we show that the continuous embedding allows for a straightforward extension of the method to open spin systems subject to dephasing, losses and incoherent drive, while preserving the key advantages of the discrete approach, such as a positive definite Wigner distribution of typical initial states. We derive exact stochastic differential equations for processes which cannot be described by the standard DTWA due to the presence of non-classical noise. We illustrate our approach by applying it to the dissipative dynamics of Rydberg excitation of one-dimensional arrays of laser-driven atoms and compare it to exact results for small systems.

An Excitation-DRR Control Approach for Wide-Beam Power Gain Pattern Synthesis

The paper maximizes the minimum power gain in a wide-beam mainlobe when satisfies both the desired sidelobe level (SLL) and the array excitation dynamic range ratio (DRR). We, firstly, set up the power gain pattern synthesis (PGPS) problem with mianlobe/sidelobe constraints and DRR constraint. With the aid of two introduced auxiliary variables, the non-convex mainlobe/sidelobe constraints are converted into linear forms. Then, these two linear constraints are written into the cost function to construct an augmented Lagrangian function of the primal optimization problem. A penalty dual decomposition based approach, which iteratively solves the primal variables in the inner loop and the dual variables in the outer loop, is proposed. The proposed algorithm estimates the power-gain-related variables and the SLL-related variables in a pseudo-analytical way while optimizing the array excitation by solving a constrained least square problem. Both linear array and planar array are simulated to assess the effectiveness and superiority of the proposed algorithm on DRR control issue by comparing it with the existing DRR reduction algorithms. Numerical results show that the proposed algorithm can obtain the highest minimum power gain in the wide-beam when satisfies both the desired SLL and the desired low DRR.

Grouping Strategies of Discrete Elements for Efficient Power Pattern Tolerance Analysis of Antennas/Radomes Using Monte Carlo Method

This work presents a simple grouping method for efficient power pattern tolerance analysis of antennas/radomes using the Monte Carlo method. The discrete elements, as antenna array elements or antenna/radome discretized meshes, are grouped into a limited number of clusters to reduce the number of independent random variables. Three grouping strategies based on Cartesian coordinates, polar coordinates, and random case are presented to group the discrete elements into eight types. A method combining two sets of results with pattern main-lobe-region and sidelobe-region optimal grouping numbers is proposed to improve the tolerance analysis precision. A 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 60 uniformly excited rectangular array antenna with excitation errors and its variants with amplitude taper or circular aperture, and a spherical radome with more than 1100 discrete meshes are considered. The results show that the proposed method can yield desirable electromagnetic (EM) performance variation ranges using 103–2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,10^{3}$ </tex-math></inline-formula> random samplings. Through grouping, the obtained EM performance interval percentages with respect to the interval analysis results are improved from 3%–6% to 47%–88% for the antenna cases and from 1%–2% to 19%–30% for the radome cases, respectively.

Optical magnetism and wavefront control by arrays of strontium atoms

By analyzing the parameters of electronic transitions, we show how bosonic Sr atoms in planar optical lattices can be engineered to exhibit optical magnetism and other higher-order electromagnetic multipoles that can be harnessed for wavefront control of incident light. Resonant $\lambda\simeq 2.6\mu$m light for the $^3D_1\rightarrow {^3}P_0$ transition mediates cooperative interactions between the atoms while the atoms are trapped in a deeply subwavelength optical lattice. The atoms then exhibit collective excitation eigenmodes, e.g., with a strong cooperative magnetic response at optical frequencies, despite individual atoms having negligible coupling to the magnetic component of light. We provide a detailed scheme to utilize excitations of such cooperative modes consisting of arrays of electromagnetic multipoles to form an atomic Huygens' surface, with complete $2\pi$ phase control of transmitted light and almost no reflection, allowing nearly arbitrary wavefront shaping. In the numerical examples, this is achieved by controlling the atomic level shifts of Sr with off-resonant ${^3P}_J\rightarrow {^3D}_1$ transitions, which results in a simultaneous excitation of arrays of electric dipoles and electric quadrupoles or magnetic dipoles. We demonstrate the wavefront engineering for a Sr array by realizing the steering of an incident beam and generation of a baby-Skyrmion texture in the transmitted light via a topologically nontrivial transition of a Gaussian beam to a Poincar\'{e} beam, which contains all possible polarizations in a single cross-section.

Compressive Sensing in Massive MIMO Array Testing: A Practical Guide

Compressive sensing (CS) has been deployed in a variety of fields including wideband spectrum sensing, active user detection, and antenna arrays. In massive multiple input multiple output (MIMO) arrays, CS has been applied to reduce the number of measurements required to verify the arrays excitation. To date, the literature has concentrated on the various methods of achieving CS and applying them to both linear and 2-D arrays, and aimed at detecting fully failed elements in an array, offering simple pass/fail testing. All follow the general approach of creating the sparsity needed for CS by subtracting the measured far field or near field of the test array from that of a “gold standard” array measured under exactly identical conditions. This article extended this work to the need for rapid but accurate reconstruction of element excitation in a production testing environment for massive MIMO arrays. The aim is to demonstrate that CS can offer accurate reconstruction of array excitation. Particularly, the work addresses the issues of optimal sampling, measurement noise, accuracy of faulty element detection, effects of beam scanning, and physical alignment of the gold standard array with the test array. We have restricted ourselves to considering production standard arrays with failure rates up to around 5% and conclude with a set of proposed modifications to the basic CS process as applied to array excitations that achieve a near 20 dB improvement in the accuracy of the reconstructed array excitation offering mean square errors (MSEs) near to −40 dB, with a sampling strategy of just 1.4% of the Nyquist rate. This is achieved with the number of measurements to array element size ratio of approximately 0.2.

Vorticity Shedding and Acoustic Resonance Excitation of a Square Tube Array: Effect of Flow Approach Angle

Abstract This paper presents an experimental investigation of the vorticity shedding and the susceptibility of acoustic resonance excitation for a square tube array with an intermediate tube spacing (i.e., pitch-to-diameter ratio (P/D) of 1.73). The tube array could be rotated about an axis normal to the flow direction so that the effect of the flow approach angle could be investigated. Various Strouhal periodicities (St) were detected, and their strength and value were dependent on the position measured within the tube bundle and the tube bundle's angular orientation. However, not all of the Strouhal periodicities measured caused self-excitation of acoustic resonance. This work illustrates the importance of considering the flow approach angle in the heat exchanger design phase to avoid the undesirable effects of acoustic resonance excitation during operation.

A compressed sensing approach for antenna array calibration

This paper presented a compressive sensing (CS) calibration technique that simultaneously measures all the element excitations of a 2×2 active phased antenna array (APAA) instantaneously. The power patterns of the rectangular 2×2 APAA element are synchronized to orthogonally cross multiplicative sub-array system applying compressive sensing in achieving an array thinning along two 1-D sub-arrays for a fixed steered beam radiation. The far field radiation pattern direction of the 2×2 APAA is examined considering the mutual effect, complex excitation of the amplitude and phase of the antenna elements placed on the x and y axes. The unwanted array excitation with errors are calibrated using minimization vector as a standard basic pursuit problem in compressive sensing technique for the 2×2 APAA calibration. The elements amplitude and phase shift variation are compared with reference state 0 in order to evaluate the faulty error array elements. The performance evaluation of this proposed technique is measured and demonstrated to validate the effectiveness of the proposed antenna calibration technique.

Synthesis of Concentric Circular Antenna Array Using Whale Optimization Algorithm

Through the ages the importance of the swarm intelligence-based algorithm has gained popularity in the field of optimization. The Whale Optimization Algorithm (WOA) is one such popular meta-heuristics nature inspired swarm intelligence-based algorithm which is well accepted for solving optimization problems, as it is simple and capable to obtain optimal results efficiently. In this paper, few benchmark functions along with radiation patterns of concentric circular antenna array are presented and their performance is optimized using WOA. Simulation results are shown by taking various benchmark functions, namely: Three hump & Six hump camel function, Ackley, Egg Crate Function, and Egg Holder Function. The capability of the WOA algorithm is also tested through pattern synthesis with respect to the thinned array as well as non-uniformly excited array for four diverse sets of CCAA geometries. When comparison is being done with respect to renowned and most popular optimization approaches like PSO, the WOA technique proves to be excellent in terms of maximum SLL suppression. Optimization results show the better capability of WOA in the field of optimization.

A Hybrid Approach for the Synthesis of Nonuniformly Spaced and Excited Linear Arrays With Strict Element Spacing Constraints

A hybrid methodology for the synthesis of nonuniformly spaced and excited linear arrays is proposed. At first, a modified genetic algorithm (GA) named linear-constraint genetic algorithm (LCGA) is discussed in this article to adapt to generalized linear-constraint optimization problems. Then, by nesting the technique of convex programming (CP) into LCGA, a hybrid optimization implementation is developed to jointly optimize the position and excitation variables. Due to the linear-constraint character of LCGA, array layouts can be exactly constrained with element spacings and the aperture size. A set of representative numerical experiments shows the effectiveness of this method to obtain very high-quality solutions.

Design for Array-Fed Beam-Scanning Reflector Antennas With Maximum Radiated Power Efficiency Based on Near-Field Pattern Synthesis by Support Vector Machine

The maximum radiation efficiency can be obtained when the feed array excitation of a reflector antenna is synthesized by the conjugate field matching (CFM) method. However, the CFM method can only get the strongly tapered feeding power distribution. This will lead to most of power amplifiers (PAs) working in low efficiency states and reduce the equivalent isotropic radiated power (EIRP) with the limited power consumption. In this work, combining the radiation efficiency and the PA efficiency, the radiated power efficiency (RPE) is defined as the new design goal and is to be raised to achieve higher EIRP. For this reason, a method based on the near-field pattern synthesis is proposed. In this method, all the ON-state PAs are required to work in the highest efficiency state. Then, with well-trained support vector machine (SVM), the ON–OFF states of the PAs are adjusted so that the reflected focal field can be better synthesized by the near-field pattern of the feed array. Thus, the loss of the radiation efficiency is minimized. As a result, the RPE is about 22% higher than that of the CFM method and about 10% higher than that of the optimum CFM truncation case.

Topological transitions driven by quantum statistics and their electrical circuit emulation

Topological phases exhibit a plethora of striking phenomena, including disorder-robust localization and the propagation of waves of various nature. While this physics is actively explored in bosonic and fermionic cases, the topological phases of anyons --- particles with fractional quantum statistics --- are largely uncharted. Here, we unveil the topological transition mediated by the particles' quantum statistics that arises for two-anyon and three-anyon excitations in a one-dimensional array described by the extended Hubbard model. As we demonstrate, the interplay of two-particle interactions and tunneling processes enables topological edge states of anyon pairs whose existence and localization at one or another edge of the one-dimensional system is governed by the quantum statistics of particles. Since a direct realization of the proposed system is challenging, we develop a rigorous method to emulate the eigenmodes and eigenenergies of anyon pairs with resonant electrical circuits.

Controlling Rydberg Excitations Using Ion-Core Transitions in Alkaline-Earth Atom-Tweezer Arrays

Scalable local control over gate operations is an outstanding challenge in the field of quantum computing and programmable quantum simulation with Rydberg-atom arrays. One approach is to use a global field to excite atoms to the Rydberg state and tune individual atoms in and out of resonance via local light shifts. In this work, we point out that photon-scattering errors from light shifts can be significantly reduced if the light shift is applied to the Rydberg state instead of the ground state, which can be realized in Rydberg states of alkaline-earth atoms using optical transitions in the ion core. As a proof of concept, we experimentally demonstrate global control of Rydberg excitations in an Yb optical-tweezer array via light shifts induced by a laser tuned near the Yb+6s→6p1/2 transition. We also perform detailed spectroscopy of the induced light shift and scattering rates of the 6sns3S1 Rydberg states and reveal the existence of satellite lines where losses from autoionization are strongly suppressed. This work can be readily extended to implement local gate operations in Rydberg-atom arrays.Received 18 October 2021Revised 27 January 2022Accepted 24 March 2022DOI:https://doi.org/10.1103/PRXQuantum.3.020326Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum information architectures & platformsPhysical SystemsRydberg atoms & moleculesTechniquesAtom & ion coolingOptical tweezersAtomic, Molecular & OpticalQuantum Information

An iPRES-W Coil Array for Simultaneous Imaging and Wireless Localized B0 Shimming of the Cervical Spinal Cord.

To develop a wireless integrated parallel reception, excitation, and shimming (iPRES-W) coil array for simultaneous imaging and wireless localized B0 shimming, and to demonstrate its ability to correct for distortions in DTI of the spinal cord in vivo. A 4-channel coil array was modified to allow an RF current at the Larmor frequency and a direct current to flow on each coil element, enabling imaging and localized B0 shimming, respectively. One coil element was further modified to allow additional RF currents within a wireless communication band to flow on it to wirelessly control the direct currents for shimming, which were supplied from a battery pack within the scanner bore. The RF signals for imaging were transferred via conventional wired connections. Experiments were conducted to evaluate the RF, B0 shimming, and wireless performance of this coil design. The coil modifications did not degrade the SNR. Wireless localized B0 shimming with the iPRES-W coil array substantially reduced the B0 RMSE (-57.5% on average) and DTI distortions in the spinal cord. The antenna radiation efficiency, antenna gain pattern, and battery power consumption of an iPRES-W coil measured in an anechoic chamber were minimally impacted by the introduction of a saline phantom representing tissue. The iPRES-W coil array can perform imaging and wireless localized B0 shimming of the spinal cord with no SNR degradation, with minimal change in wireless performance and without any scanner modifications or additional antenna systems within the scanner bore.

Design optimization of linear arrays and time‐modulated antenna arrays using meta‐heuristics approach

AbstractThis article presents an approach to design a non‐uniformly excited linear array antenna (LAA) and an alternate solution to LAAs in the form of time‐modulated linear arrays (TMLA) for optimum far‐field radiation pattern synthesis. The performance analysis of both the antenna arrays is studied, and the advantages and limitations of the proposed design approaches are presented with numerical outcomes. The far‐field radiation pattern is optimized to reduce the interference by simultaneously lowering the sidelobe levels and increasing the directivities of LAAs and TMLAs. A recently proposed meta‐heuristics computation technique called whale optimization algorithm (WOA) is employed to get the optimal results. The current excitation amplitude and the inter‐element spacing of the 16‐element LAA are optimized with WOA to attain the desired results. However, due to the large dynamic range ratios (DRRs) of excitation weights, array feed network complexities are increased, which restricts the design of typical LAAs. TMLAs can be regarded as an alternative solution where the problem of large DRRs as well as the design complexities of LAAs are eliminated. The concept of ‘time’ is vital in time‐modulation as it plays the role of an added degree of freedom realized by periodically turning ON and OFF the radio‐frequency switches with an electronic control circuit to achieve an enhanced array radiation pattern. WOA is utilized to determine the optimal switch‐ON time periods for each array element and the optimal inter‐element spacing of a 16‐element TMLA. A set of numerical results validates the advantages of TMLAs over LAAs, and the limitations of TMLAs with respect to LAAs are also indicated. The performance of both the arrays is then compared with other published literature results to establish the superiority of the proposed approach.

Pattern synthesis of linear and ring arrays with minimum number of elements using FFT and Bessel transformation

In antenna engineering, to reduce the final cost of array design, it is often necessary to design an array with the minimum number of elements. So, proper selection of the number of array elements and the location of the elements are two important factors in array design. In this work, a novel analytical approach for designing an array with optimal parameters is described. The Nyquist–Shannon sampling theorem is used to determine the number of array elements and the distance between them. The array's excitation coefficients are then determined using the recursive least square approach and the Bessel transform of the array factor. It is also demonstrated that the introduced procedure can be extended to include the concentric ring arrays. Several practical arrays are evaluated to verify the performance of the suggested approach. The results show that the introduced approach is a good candidate for designing practical arrays with acceptable accuracy.