Antenna Array Geometry Research Articles

A Generalized Array Factor for Time-Modulated Hexagonal Based Antenna Array Geometry with Novel Trapezoidal Switching

A Generalized Array Factor for Time-Modulated Hexagonal Based Antenna Array Geometry with Novel Trapezoidal Switching

ReLoki: A Light-Weight Relative Localization System Based on UWB Antenna Arrays.

Ultra Wide-Band (UWB) sensing has gained popularity in relative localization applications. Many localization solutions rely on using Time of Flight (ToF) sensing based on a beacon-tag system, which requires four or more beacons in the environment for 3D localization. A lesser researched option is using Angle of Arrival (AoA) readings obtained from UWB antenna pairs to perform relative localization. In this paper, we present a UWB platform called ReLoki that can be used for ranging and AoA-based relative localization in 3D. To enable AoA, ReLoki utilizes the geometry of antenna arrays. In this paper, we present a system design for localization estimates using a Regular Tetrahedral Array (RTA), Regular Orthogonal Array (ROA), and Uniform Square Array (USA). The use of a multi-antenna array enables fully onboard infrastructure-free relative localization between participating ReLoki modules. We also present studies demonstrating sub-50cm localization errors in indoor experiments, achieving performance close to current ToF-based systems, while offering the advantage of not relying on static infrastructure.

A Theoretical Design of Angular-Phased Broadband Antenna Array for Submillimeter Wave Applications

In this article, a broadband semicircular antenna array geometry was examined, along with its design and configuration in the submillimeter wave range (9.35-42.89 GHz). The work has been divided into two prime phases; in the first phase of work, an innovative angular-phased 1 : 4 broadband power divider has been presented in which its isolation, insertion, and return losses are investigated. In the next phase, the proposed power divider was used to configure a 4-element antenna array, and its theoretical analysis was carried out. The angular path difference in the array was used to introduce phase difference in between the antenna elements to minimize the mutual coupling and to optimize the narrow beamwidth. Using geometry and fundamental array theory, the array factor of a novel broadband array configuration has been derived and analytically investigated.

Sparse Tiled Planar Array: The Shared Multibeam Aperture for Millimeter-Wave Joint Communication and Sensing

Multibeam planar arrays are investigated as shared apertures for dual functionality in millimeter-wave (mmWave) joint communication and sensing (JCAS), providing time division duplex communication and full-duplex sensing with steerable beams. The conventional uniform planar arrays (CUPA)s have limited angular resolution, whereas the sparse planar arrays (SPA)s are often very costly to implement. In order to have a low-cost aperture with high angular resolution, we propose to design a sparse tiled planar array (STPA) shared aperture. Our proposed solution is modular tiling and uniform at the subarray level but sparse at the aperture level. The modular tiling and sparse design of a planar array are non-convex optimization problems; however, we exploit the fact that the more irregularity of the antenna array geometry, the less the side lobe level (SLL). In a JCAS scenario, we compare the performance of STPA, CUPA. and SPA, regarding the spectral efficiency of a line-of-sight (LoS) included communication link, detection loss rate, and detection accuracy rate for sensing, and the blockage time in case of an overlapping communication and sensing beam. The SPA for comparison has the same size and beamwidth as STPA, but less average SLL and less modular design. The results show that the same spectral efficiency is achieved in the communication link for CUPA, SPA, and STPA. The effect of a smaller beamwidth of the STPA and SPA is reflected in the lower detection loss rate of them compared to that of the CUPA, but the side lobes of these sparse solutions result in errors in the association of the detected and true targets and hence a reduction in the detection accuracy. In such a multibeam solution for JCAS, it is critical to study blockage time, and we show that the STPA and SPA have a 40% shorter blockage time compared to the CUPA when a blocker moves across the LoS of the communication link. Therefore, STPA is a trade-off solution between CUPA and SPA, since it has uniformly distributed antennas within the subarrays as in CUPA, but a sparse solution in the whole aperture as in SPA, which guarantees the same beamwidth and sensing performances as a SPA.

Two-Step Decoupling Design of a Microstrip Antenna Array by Using Waveguided Complementary Split-Ring Resonators and a Fully Connected Neural Network

To suppress the mutual coupling between closely-spaced patches, we propose a two-step decoupling design approach for a microstrip antenna array with the dimensions of 44.9 × 30.495 mm2. The first step is designing a decoupling unit on the basis of waveguided complementary split-ring resonators (WCSRRs) to improve isolation. The second step is presenting an optimization method by using a fully connected neural network (FCNN) to enhance design efficiency. By inserting WCSRRs structure between two patches with the edge-to-edge distance of 0.24λ0 (port-to-port distance with 0.66λ0), where λ0 is the wavelength of free space at a resonant frequency of 9 GHz, the mutual coupling can be reduced to −29.38 dB, which is confirmed by the EM simulation. We use the simulation results of the array geometries and EM performances to train FCNN at first and then use the trained FCNN to predict the array geometric parameters for the optimal EM response when the edge-to-edge distance between patches is further reduced to 0.21λ0 and 0.18λ0 (port-to-port distance reduced to 0.60λ0 and 0.56λ0). The measured isolation of the predicted microstrip antenna array is increased to 41.05 dB and 52.33 dB, respectively. Compared to the EM simulation, our FCNN approach has a higher accuracy and lower computational complexity. Therefore, the proposed array predicted by FCNN has a better decoupling performance. All the simulated and predicted results are validated via the measurement to demonstrate the effectiveness of our design scheme. The advantages of our work include the good decoupling performance of the proposed WCSRRs and the convenient optimization of the FCNN from physical response to optimal antenna array geometry design.

DOA Estimation Based on Convolutional Autoencoder in the Presence of Array Imperfections

Array imperfections may exist in an antenna system subject to non-ideal design and practical limitations. It is difficult to accurately model array imperfections, and thus complicated algorithms are usually inevitable for model-based methods to estimate the direction of arrival (DOA) with imperfect arrays. Deep neural network (DNN)-based methods do not need to rely on pre-modeled antenna array geometries, and have been explored to handle flawed array models because of their better flexibility than model-based methods. The DNN autoencoder (DAE) method has been proposed for the array imperfection problem, which decomposes the input into multiple components in different spatial subregions. These components have more concentrated distributions than the original input, which avoid a large number of connections and nodes used in the layers to realize DOA estimation classifiers. In this paper, we study the convolutional AE (CAE) method that substantially focuses on the learning of local features in a different manner from the previous DAE method. The advantage of the convolutional operation using a kernel in CAE is to capture features in a more efficient manner than the DAE, and thus be able to reduce the number of parameters that are required to be trained in the neural networks. From the numerical evaluation of DOA estimation accuracy, the proposed CAE method is also more resistant to the noise effect than the DAE method such that the CAE method has better accuracy at a lower signal-to-noise ratio.

Direct Conversion of Hybrid Precoding and Combining From Full Array Architecture to Subarray Architecture for mmWave MIMO Systems

Hybrid precoding and combining for millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems with subarray (SA) architecture is a promising technology for 6G because of their low complexity, cost, and power consumption compared to the full array (FA) architecture. This paper proposes an iterative algorithm for designing hybrid precoding and combining for the SA architecture. It is called direct conversion of iterative hybrid precoding and combining from FA to SA (DCIFS). The proposed algorithm involves an iterative process that begins by designing a hybrid precoding and combining matrix for the FA structure and then converts it into an SA matrix by setting certain entries to zero while achieving better performance. It does not depend on the antenna array geometry, unlike other techniques such as the orthogonal matching pursuit (OMP) hybrid precoding and combining approach. We investigate the proposed algorithm with two scenarios. In the first scenario, we use the proposed DCIFS scheme only at the base station (BS) and the iterative FA hybrid scheme at the mobile station (MS), whereas in the second, we use the proposed DCIFS scheme at both the BS and the MS. Simulation results demonstrate that the proposed design approach achieves a spectral efficiency comparable to that of the FA hybrid design counterpart, especially for a large system, while maintaining low complexity. For example, when SNR= 0 dB and the number of transmitted streams ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_s</i> ) = 2, the proposed algorithm provides about 1.5 bps/Hz spectral efficiency gain compared to the OMP hybrid design for the first scenario. Moreover, when the number of iterations is low and the number of BS antenna and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_s</i> is high, the proposed approach outperforms the conventional SA hybrid design in terms of spectral efficiency with the same hardware complexity.

Multi-antenna 3D pattern design for millimeter-wave vehicular communications

The transformation of the automotive industry towards ubiquitous connection of vehicles with all kind of external agents (V2X) motivates the use of a wide range of frequencies for several applications. Millimeter-wave (mmWave) connectivity represents a paramount research field in which adequate geometries of antenna arrays must be provided to be integrated in modern vehicles, so 5G-V2X can be fully exploited in the Frequency Range 2 (FR2) band. This paper presents an approach to design mmWave vehicular multi-antenna systems with beamforming capabilities considering the practical limitations of their usage in real vehicular environments. The study considers both the influence of the vehicle itself at radiation pattern level and the impact of the urban traffic on physical layer parameters. Connectivity parameters such as Signal-to-Interference-plus-Noise Ratio (SINR) and outage probability are optimized based on the array topology. A shaped beam in the vertical plane based on three preset radiating elements is proven to be robust enough against self-scattering effects on the vehicle body. Regarding the horizontal geometry, four panels on the roof's edges provide good coverage and link quality. The number of horizontal antennas per panel tightly depends on the required values of the link quality metrics, potentially leading to a non-uniform geometry between sides and front or back panels.

Минимизация нижней границы Крамера-Рао для построения антенных решеток с направленными излучателями для повышения точности оценок угловых координат радиосигналов

The use of antenna arrays equipped with digital signal processing units is a promising way to increase the throughput, noise immunity of modern wireless information transmission systems. The spatial diversity of the antenna is the main advantage of this approach which makes it possible to estimate the spatial coordinates of radio signals with subsequent beamforming. It is well known that the insufficient knowledge of the influence of the array geometry together with various types of antenna elements (such as a dipole, a patch, etc.) may be a cause reducing the accuracy of such systems. The article describes an approach aiming at reducing direction-of-arrival estimation errors of radio signal sources by means of optimal antenna array geometries. In particular, the Cramer-Rao lower bound is used for the task. The quantity sets a limit below which one or another algorithm for estimating the spatial coordinates of signal sources cannot descend for a particular geometry of the antenna array. The expressions based on the Cramer-Rao lower bound are derived which describes the dependence of the variance of direction-of-arrival estimation errors on the location of the array elements in the Cartesian coordinate system, i.e. along the x, y, z axes. In addition, the function of the radiation patterns of individual antennas is taken into account in the obtained formulas. Additionally it is considered that the antenna elements are directional. Therefore, the proposed technique is aimed at reducing the variance of direction-of-arrival estimation errors of statistical algorithms with superresolution by minimizing the obtained new formulas. As a result, the optimal locations of antenna elements along the x, y, z axes are calculated. In the paper, new geometries of antenna arrays have been obtained according to the proposed approach. In particular, two- and six-element arrays are researched, which are compared with equally spaced cylindrical ones. Graphs of the error variance of the Cramer-Rao boundary are presented, as well as a statistical study of the MUSIC method. It is shown that the magnitude of errors is reduced by new antenna arrays in all the researching scenarios. Thus the antenna arrays geometries obtained in this paper allow improving the accuracy of algorithms for estimating the angular coordinates of radio signals with superresolution.

Robust adaptive beamforming based on covariance matrix reconstruction via correlation coefficient of steering vector

Traditional adaptive beamformers are sensitive to model mismatch and they have poor performances when the input signal-to-noise ratio (SNR) is close to or more than interference-to-noise ratio (INR). In this letter, a novel robust adaptive beamforming (RAB) algorithm based on twice interference-plus-noise covariance (INC) matrix reconstruction is proposed. Firstly, the desired signal (DS) steering vector is estimated by the alternating projection algorithm based on the antenna array geometry and angular sector prior information. Then, the proposed method obtains the eigenvalue corresponding to DS by correlation coefficient and takes the place of it by noise power to obtain the first INC matrix. Furthermore, the second precise covariance matrix is reconstructed based on the theoretical INC matrix expression. The interferences powers are estimated by the theoretical formulation of the interference covariance matrix (ICM), which is derived from the first INC matrix. The simulation results demonstrate that the proposed algorithm achieves good performance especially when the input SNR is high, and its performance is close to the optimal beamformer in the case of look direction error.

RETRACTED ARTICLE: Circular antenna array optimization using modified social group optimization algorithm

Antenna arrays have potential applications in Radar, mobile, broadcasting, astronomy and other defense and commercial platforms. The design of antenna arrays is essential as they are capable of controlling the radiation pattern in terms of sidelobe level (SLL), beamwidth (BW), nulls and beam steering. Among several geometries of antenna arrays, the circular antenna arrays have the advantage in terms of inherent capability to control the phase implicitly. In this paper, circular antenna array synthesis is presented using novel metaheuristic techniques like the Social Group Optimization Algorithm (SGOA) and Modified SGOA (MSGOA). The main objective of the synthesis process is to synthesize radiation patterns with suppressed SLL while the BW being equal to the uniform distribution. A comparative study is performed to analyze the performance of various synthesis techniques like amplitude only, inter-element spacing only, and amplitude spacing. The MGSOA and SGOA have proved to be performing well in accomplishing the objective. Further, the CAA synthesis problem is translated into single-variable and multivariable optimization problems following which the obvious advantage associated with the inclusion of additional variable as an additional degree of freedom is demonstrated. The simulation is carried out in Matlab®, and results are analyzed using the plotted radiation patterns.

Direction finding and beamforming using cylindrical array of dipole antennas in the presence of cylindrical scatterer/reflector including the mutual coupling effect

Three-dimensional dipole arrays are normally used at the proximity of a reflective structure. Filamentary short-circuited dipoles are proposed to model the effect of the reflector structure. The computational burden is significantly reduced by using mutual impedance matrices. An analytical method of modelling the effect of the cylindrical reflector in a three-dimensional cylindrical geometry of dipole antenna arrays is introduced both for direction finding and beamforming applications in the presence of mutual coupling. The results of the implementation of the MUSIC (multiple signal classification) direction-finding algorithm show that the proposed model for accounting the cylindrical reflector, in the presence of a mutual coupling effect, has the required efficiency and reduced root-mean-square-error (RMSE). Monte-Carlo simulations for the beamforming algorithm are conducted to evaluate the signal-to-interference ratio (SIR) values in the presence of a cylindrical reflector and the results show that the model has the desired performance. The whole process of beamforming and pattern generation has been verified through high-frequency structural simulator (HFSS) simulation. The simplicity, adequate precision and low computational cost of this method can be appropriately used in the cylindrical reflector/scatterer in three-dimensional geometries, especially for base station applications.

Arraymetrics: Authentication Through Chaotic Antenna Array Geometries

Advances in computing have resulted in an emerging need for multi-factor authentication using an amalgamation of cryptographic and physical keys. This letter presents a novel authentication approach using a combination of signal and antenna activation sequences, and most importantly, perturbed antenna array geometries. Possible degrees of freedom in perturbing antenna array geometries affected physical properties and their detection are presented. Channel estimation for the plurality of validly authorized arrays is discussed. Accuracy is investigated as a function of signal-to-noise ratio (SNR) and number of authorized arrays. It is observed that the proposed authentication scheme can provide 1% false authentication rate at 10 dB SNR, while it is achieving less than 1% missed authentication rates.

Flower Pollination Heuristics for Parameter Estimation of Electromagnetic Plane Waves

For the last few decades, the parameter estimation of electromagnetic plane waves i.e., far field sources, impinging on antenna array geometries has attracted a lot of researchers due to their use in radar, sonar and under water acoustic environments. In this work, nature inspired heuristics based on the flower pollination algorithm (FPA) is designed for the estimation problem of amplitude and direction of arrival of far field sources impinging on uniform linear array (ULA). Using the approximation in mean squared error sense, a fitness function of the problem is developed and the strength of the FPA is utilized for optimization of the cost function representing scenarios for various number of sources non-coherent located in the far field. The worth of the proposed FPA based nature inspired computing heuristic is established through assessment studies on fitness, histograms, cumulative distribution function and box plots analysis. The other worthy perks of the proposed scheme include simplicity of concept, ease in the implementation, extendibility and wide range of applicability to solve complex optimization problems. These salient features make the proposed approach as an attractive alternative to be exploited for solving different parameter estimation problems arising in nonlinear systems, power signal modelling, image processing and fault diagnosis.

Low Complexity Hybrid Precoding and Combining for Millimeter Wave Systems

In millimeter-wave (mmWave) systems, hybrid precoding/combining architectures are an attractive low-complexity alternative to the use of fully digital precoding. This is because of the reduction in the number of Radio-Frequency (RF) and mixed-signal hardware components. Hybrid precoding/combining design involves a combination of analog and digital processing that enables both beamforming and spatial multiplexing gains in mmWave systems. This paper presents an algorithm for hybrid precoding and combining designs in mmWave systems. The proposed design does not depend on the antenna array geometry, unlike the orthogonal matching pursuit (OMP) hybrid precoding/combining approach. Moreover, this algorithm allows hybrid precoders/combiners to perform close to the known optimal performance of unconstrained digital precoders and combiners. Simulation results verify that the proposed hybrid precoding/combining scheme outperforms the previous methods in the literature in terms of bit error rate (BER) and achievable spectral efficiency with lower complexity.

Design and Analysis of Phased Array System by MATLAB Toolbox

An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services. In this paper toolboxes of MATLAB will use for the phased array system for different purposes of extraction of information about a validate results for antenna array and a comparison is made between different antenna array geometries, also this paper provides the background of the newly developed MATLAB Phased Array Toolbox. So, some effective parameters like the changing element spacing and the number of elements and the geometrical shape of the array on the antenna array radiation pattern along with the gain have been studied. The Phased Array Toolbox of MATLAB has also been used to validate the results.

AoD-based localization with cots millimeter-wave devices

Radio frequency-based localization techniques have undergone rapid development in recent years. However, existing localization systems on commercial Wi-Fi devices are either impractical or inaccurate. The newly emerging WiGig devices use millimeter-wave signals to communicate. As they have much more antennas than Wi-Fi devices, and they also have a higher angular resolution. However, because of cost limitations, commercial WiGig devices use analog beamforming, and the channel response of each antenna is unavailable. In this work, we propose WiGLoc a system for WiGig devices that provides accurate localization. To achieve this goal, we model the RSS of the antenna array, from which the CSIs of individual antennas are recovered. Then, the antenna array is calibrated, and the array geometry is obtained. WiGLocestimates AoDs from WiGig APs to the target with antenna CSIs and array geometry to localize the target. Experimental results show that the average 3D tracking and 2D localization errors of WiGLocare only 6 and 27 cm, respectively; whereas those of the state-of-the-art beamforming approach are 11 and 44 cm, respectively.

On the Impact of Antenna Array Geometry on Indoor Wideband Massive MIMO Networks

Multi-user massive multiple-input-multiple-output (massive MIMO) will play a key role in future wireless communication networks. Since spatial channel diversity is the fundamental merit of this technique, high channel correlation may significantly restrict its abilities. This study investigates the impact of channel correlation on a prototyped massive MIMO network with the objective to identify an antenna array geometry which has reduced mutual coupling and channel correlation. To this end, a highly efficient directional wideband single antenna element was designed for the antenna arrays and the user equipments (UEs). The designed array geometry is tested in an experimental indoor wideband massive MIMO setup. Important system parameters, such as channel correlation, power delay profile, and average received power from the UEs, are studied by analyzing the measured channel data. Furthermore, system-level simulations and network capacity calculations are performed based on the measured channel data to evaluate the performance of the prototyped antenna arrays. A regular array was also fabricated and used for benchmarking comparison. Moreover, a power control algorithm is introduced for the uplink, which was shown to improve the network capacity by up to 3 dB. The results demonstrate that the introduced antenna array outperforms the uniform antenna array in terms of mutual coupling and channel capacity.

Optimal Design of Aperiodic Reconfigurable Antenna Array Suitable for Broadcasting Applications

An aperiodic reconfigurable microstrip antenna array is designed to serve as a DVB-T base station antenna operating in a single broadcasting channel. The antenna array is optimized at 698 MHz (center frequency of DVB-T channel 49) to concurrently achieve a particular radiation pattern shaping with high forward gain, main lobe tilting and null filling inside the service area, as well as low sidelobe level outside the service area, and low standing wave ratio at the inputs of all the array elements. To concurrently satisfy all the above requirements, both the geometry dimensions and the array feeding weights (amplitudes and phases) are optimized, thus leading to a complex multi-variable and multi-objective problem. The problem is solved by applying a recently developed particle swarm optimization (PSO) improved variant, called PSO with velocity mutation, in conjunction with the CST software package, which is employed by the PSOvm every time a full-wave analysis is required. Furthermore, all the optimization methods found in the CST environment are compared with the PSOvm. The results show that the PSOvm is capable of producing an antenna array geometry, which is closer to the predefined requirements than the geometries derived by the rest of the optimizers, in the least amount of computational time.

Aerial Access and Backhaul in mmWave B5G Systems: Performance Dynamics and Optimization

The use of unmanned aerial vehicle (UAV)- based communication in millimeter-wave (mmWave) frequencies to provide on-demand radio access is a promising approach to improve capacity and coverage in beyond-5G (B5G) systems. There are several design aspects to be addressed when optimizing for the deployment of such UAV base stations. As traffic demand of mobile users varies across time and space, dynamic algorithms that correspondingly adjust the UAV locations are essential to maximize performance. In addition to careful tracking of spatio-temporal user/traffic activity, such optimization needs to account for realistic backhaul constraints. In this work, we first review the latest 3GPP activities behind integrated access and backhaul system design, support for UAV base stations, and mmWave radio relaying functionality. We then compare static and mobile UAV-based communication options under practical assumptions on the mmWave system layout, mobility and clusterization of users, antenna array geometry, and dynamic backhauling. We demonstrate that leveraging the UAV mobility to serve moving users may improve the overall system performance even in the presence of backhaul capacity limitations.