Large Antenna Research Articles

Beamspace Modulation for Near Field Capacity Improvement in XL-MIMO Communications

The spatial degrees of freedom (DoFs) greatly increase in the near-field region of millimeter wave or terahertz multiple-input multiple-output communications with extremely large antenna arrays (XL-MIMO). To employ the increased spatial DoFs, a beamspace modulation (BM) strategy is introduced to the near field of XL-MIMO. BM can work with a fixed small number of RF chains. It exploits the increased spatial DoFs as modulation resources for capacity improvements. The achievable spectral efficiency and its asymptotic capacity are analyzed. Both theoretical and simulation results show that the proposed BM strategy considerably outperforms the existing benchmark that only selects the best beamspace for data transmission in terms of spectral efficiency.

Optimized transmit antenna selection and self-attention based convolutional resource allocation model for massive MIMO technology

Massive multiple input and multiple output (MIMO) plays an important role in enhancing the transmission reliability and capacity of the transmitting channel. However, the resource allocation (RA) and transmit antenna selection (TAS) scheme are essential for massive MIMO systems to reduce implementation costs and complex operations. Because the presence of a large antenna consumes enormous resources that must be reduced in order to develop a user-friendly model. Hence, this article introduces a novel TAS and RA scheme in a massive MIMO system that can enhance communication performance efficiently. In this study, an improved sheep flock optimization algorithm (ISFOA) is first emphasized to select the efficient antenna, thus effectively minimizing the cost and the design complexity. Then, a novel deep learning (DL) based self-attention aided deep convolutional neural network (SA-DCNN) model for the stable allocation of resources to all available users is proposed. Thus, the user equipment (UE) can develop a better quality path and reduce the power consumption of the entire system. In the experimental scenario, the performance of the proposed model is compared with an existing technique based on sum rate, spectral efficiency (SE) and energy efficiency (EE) by varying base station (BS) antennas, varying user, signal to noise ratio (SNR), and sub-carriers along with the computational performance. Particularly, when the SNR=10 dB, the proposed model obtains the SE of about 50 bits/s Hz compared to the existing techniques.

Investigation of Planar Isolators for Mutual Coupling Reduction in Two-Dimensional Microstrip Antenna Arrays

The design of isolators to reduce mutual coupling in large two-dimensional antenna arrays is complex and requires significant computational effort. This work attempts to alleviate this problem by applying different types of planar isolators in different orientations and experimenting first with two-element microstrip antenna arrays. A U-shaped planar transmission line isolator, a U-shaped planar transmission line-based destructive ground structure, and a planar neutralization line structure are designed to reduce E-plane or H-plane coupling in two-element microstrip antenna arrays. A mutual coupling reduction of approximately 6 dB is achieved. Four combinations of these planar isolators are compared and analyzed in a four-element microstrip antenna array. An optimal combination is then obtained by using two reversely placed U-shaped line isolators, which reduce the mutual coupling by more than 6.1 dB. The study is also extended to a 5 × 5 antenna array. Similar results of mutual coupling reduction are obtained. In addition to simulation, both two-element and 25-element microstrip antennas have been constructed and tested. The agreement of the simulation results with the measured results confirms the effectiveness of the decoupling structures.

Wideband multibeam mushroom antenna array with low‐temperature cofired ceramic‐integrated pillbox transition for millimetre‐wave applications

AbstractThis article presents a millimetre‐wave (MMW) wideband multibeam antenna array with a pillbox transition using multilayer low‐temperature cofired ceramic (LTCC) technology. The mushroom structure with dual resonant modes offers wideband performance for radiating array, while an integrated pillbox reflector achieves multibeam scheme. To reduce the design complexity of electrically large pillbox system, two popular pillbox transitions are investigated with a unit model method. The proposed unit model can be used to predict the transmission performance of pillbox reflector in any incident angle. Moreover, the mushroom antenna array and power divider fed by quasi‐TEM wave are also designed using unit model, greatly simplifying the design of electrically large pillbox antenna array. In the final design, the long‐slot pillbox transition, rather than multi‐slot transition, is selected due to its ultrawideband performance and simple structure. The proposed LTCC prototype is analysed and fabricated, obtaining a good agreement between simulation and measurement. The measured results show a −10 dB impedance bandwidth of 17.6% from 31 to 37 GHz, and five beams with ±45° scanning range is achieved with sidelobe level lower than −10 dB.

Large Frequency Ratio Antennas Based on Dual-Function Periodic Slotted Patch and its Quasi-Complementary Structure for Vehicular 5G Communications

Dual-function periodic slotted patch and its quasi-complementary structure in designing large frequency ratio antennas for vehicular 5G communications are presented in this paper. Firstly, a circular patch with periodic circular slots is employed as a partially reflecting surface (PRS) antenna in the millimeter-wave band. Simultaneously, the circular slotted patch is operated in the microwave band as a patch antenna, achieving dual functions. It is flexible to design the two antenna parts due to their polarization orthogonality. In the next place, with similar working principles, its quasi-complementary structure that contains periodic connected circular patches is also utilized for the large frequency ratio antenna design. As the proof of concept, two large frequency ratio antennas working in the 3.5-GHz and 28-GHz bands with a frequency ratio of 8 for 5G applications were designed. Finally, for verification, a periodic slotted patch antenna was fabricated and measured. Good agreement between the measured and simulated results is found. Measured -10-dB impedance bandwidths of 6.25% (3.41–3.63 GHz) and 20.57% (24.21–29.76 GHz), and measured peak antenna gains of 8.14 dBi and 14.04 dBi are obtained at the lower and upper bands, respectively. The antennas can be integrated solutions for vehicular-platform 5G microwave and millimeter-wave wireless communications.

A 1 mm ×1 mm CGM System on Die Achieving 1.65-nA/mM In Vivo Resolution and 0–40-mM/L Detection Range With ΔΣ Backscatter Technique

Diabetes has become a leading cause of death and disability all over the world. Continuous glucose monitoring (CGM) based on wireless power transfer (WPT) and backscatter communication enables wireless real-time telemetry to control glycemic levels in a long term. However, conventional backscatter techniques in CGM systems converted the sensing current into a bit stream or a frequency signal to switch the antenna, leading to two drawbacks: 1) Large power-harvesting antennas are required to complement the power loss in data converting and antenna switching and 2) Both the resolution and detection range are limited even with a high-performance glucose sensor. In this work, we propose a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta\Sigma$</tex-math> </inline-formula> backscatter technique to demonstrate a system on die (SoD) within a 1 <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> 1-mm on-chip antenna. Implemented in the 65-nm CMOS process, the proposed SoD achieves a telemetry error less than 0.25% with little impact on WPT, as well as a wide detection range of 0–40 mM/L. In vivo experimental results show that the CGM SoD realizes a resolution of 1.65 nA/mM.

Adaptive Non-Uniform Hybrid Beamforming for mmWave Train-to-Ground Communications in High-Speed Railway Scenarios

Higher frequency bands, especially millimeter wave (mmWave), are a key enabler for future high speed railway (HSR) wireless communication systems. Hybrid analog and digital beamforming (HBF) schemes operating at mmWave frequency bands can exploit the sparse nature of the channel by using large scale antenna arrays (LSAs) to shape multiple beams that overcome the severe path loss. However, due to the long and straight geometric characteristic of the rail track, there is a significant variance in the train-to-ground communication rate when the train is near or far from the BS. To address this issue, a novel hybrid beamforming scheme is developed based on a non-uniform beam design. We first model and investigate different beam design schemes in terms of spectral efficiency. Then, an efficient straight route based adaptively analog beamforming scheme with the non-uniform beam is proposed for HSR, which is designed to resist path loss. Finally, an adaptive non-uniform HBF algorithm based on the orthogonal matching pursuit method (OMP) is developed to minimize the rate gap between different locations by selecting the appropriate predefined beams. Numerical results show that the proposed hybrid beamforming scheme can efficiently ensure signal coverage, and reduce the variance of the train-to-ground communication rate along a straight track route.

Multiple-Frequency Preconditioned Iterative Inverse Source Solutions

Inverse source formulations relate unknown equivalent radiation sources to given field observations, which are commonly obtained from measurements. After discretization, the linear operator equation is advantageously solved in the form of an appropriate positive semidefinite normal system of equations. Several preconditioning strategies for the iterative solution of such linear systems of equations are investigated in this article. Observation point density-based preconditioners balance the effect of the constraint equations and speed up the solution process for globally irregular sample location distributions. Reduced-accuracy approximations of the radiation operator based on propagating plane-wave expansions of the pertinent Green’s functions can speed up the operator evaluation considerably. They are used within inner–outer iterative solvers or, even more efficiently, within a two-step iterative solution of the inverse source problem. Multiple-frequency inverse source solutions are considerably accelerated by start vector estimations from already available solutions for other nearby frequencies, where in particular a modified Galerkin approach is found to be very effective. The presented accelerated iterative solution approaches achieve the same accuracy levels as its not accelerated counterparts. They are validated and evaluated for a variety of near-field (NF) and far-field (FF) observation data of different antennas, whereby the benefits of the introduced solution approaches are of particular importance for large antennas with many unknowns.

On the Fine Resolution of Antenna Topologies

The emergence of massive multiple-input-multiple-output, ray-based channel models and millimeter wave systems makes it timely to take a new look at the resolution of different antenna topologies. Hence, we derive a novel approach to evaluate the fine resolution of large antenna arrays. The approach is general, tractable for arbitrary layouts and is based on a bivariate Taylor series expansion of the normalized interference between two closely separated rays. The technique is applied to several topologies in both space-constrained and unconstrained scenarios. The resulting expressions and corresponding results give insight into the relative ability of the arrays to resolve rays and provide a simple performance hierarchy for typical scenarios.

Stochastic geometry modelling and analysis for cooperative NOMA with large transmit antennas for 5G applications and beyond

AbstractAmong the technologies that have made 5G wireless communication successful are non‐orthogonal multiple access (NOMA) and cooperative NOMA. The distinction is that cooperative NOMA adds coding schemes to improve performance. Nevertheless, research on cooperative NOMA has primarily used theoretical correlation‐based stochastic models (CBSM) instead of geometric‐based stochastic models (GBSM) that represent suitable channel conditions by including characteristics like path loss, delay profile, and angle of arrival in the model. This paper connects the low adoption of GBSM is due to computational challenges. Given this, it is essential to assess cooperative NOMA that employs GBSM with large antenna transmitters to meet future 5G expectations. The cooperative NOMA system's transmitter is modelled as a uniform rectangular array and a novel channel realisation is proposed for analysis. The location vector of the antenna using the physical dimension of the array is defined to reduce computational problems. Results shows that the average bit‐error performance of GBSM matches that of CBSM at the same antenna element separation, but the spatial correlation between antenna elements significantly impacts the outage probability and average achievable rates of GBSM performance. Enhanced GBSM performance by increasing antenna separation at the transmitter above one‐eighth wavelength.

An Integrated Structure Analysis Method of Active Surface Antenna by Using the Simplified Actuator

The main surface of a large reflector antenna is composed of thousands of panels, which are inevitably deformed under natural load, leading to a great deterioration of electrical performance of the antenna. The active surface technique is an effective method to compensate antenna deformation error and has been widely used. The actuator is a complex component, it has not been established in the antenna structure analysis model, which limits the theoretical analysis ability of the active surface technology. To solve this problem, an integrated structure analysis method of active surface antenna by using the simplified actuator is proposed. First, according to the supporting characteristics and adjusting function of the actuator, the complex actuator is simplified a simple structure of support beams, support truss and adjustment beam. Second, the finite element model of the active surface antenna including the simplified actuator is established. Then, the relationship between the adjustment value (load) of adjustment beam and the deformation of the antenna structure is deduced, and the integrated analysis method for realizing the active adjustment of panels is established. Finally, the model and adjustment analysis method of the active surface antenna in this paper is applied to an 8 m antenna, and satisfactory structural analysis results are obtained, which shows the effectiveness and universality of the method, and provides a reference for the modeling and adjustment analysis of the active surface antenna.

Outcomes of the PERIOD project on In-Space Manufacturing, Assembly and Refuelling Technologies

Traditionally, satellites and other space-specific assemblies (e.g., antennas, spacecraft, etc.) are built on Earth and then sent into orbit. New approaches are pursuing direct on-orbit manufacturing and assembly using robotics, autonomy, and modularity. The advantages are many, ranging from virtually unlimited overall volume and design of large satellite antennas to numerous options for building larger space infrastructures such as large reflectors and modular space stations. In addition, in-space manufacturing and assembly (ISMA) technologies can enable the upgrade and repair of existing spacecraft and satellites already in orbit, promoting the sustainable use of space through plug-and-play modularity. The PERIOD project is pursuing a concept in which an orbital demonstrator is being developed for satellite manufacturing and assembly, as well as docking and refuelling experiments. This paper describes the background of the development, the PERASPERA building block technologies ESROCOS (European Space Robotics Control and Operating System), ERGO (European Robotic Goal-Oriented Autonomous Controller) and InFuse (Data Fusion) used, the test setup of the demonstrator and first results. The successful implementation and validation of ISMA technologies will lead to the generation of independent European capacities allowing Europe to build future orbital infrastructure and to be competitive on the ISMA markets

A Ka-Band 64-Element Deployable Active Phased-Array TX on a Flexible Hetero Segmented Liquid Crystal Polymer for Small Satellites

A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Ka$</tex-math> </inline-formula> -band 64-element deployable active phased-array transmitter (TX) on a hetero segment liquid crystal polymer (LCP) substrate for small satellites is proposed. The proposed phased-array TX achieved a large array size implementation and a small form factor with integrated six-layer and two-layer LCP substrates. Antenna and transmission line designs considering hetero layer structure are presented in detail. Achieving 46.7 dBm electronically isotropically radiated power (EIRP), the proposed phased-array TX can support 256-APSK DVB-S2X. As a result, the proposed deployable active phased-array TX successfully realizes low-launch cost with a 9.65 g lightweight and large antenna aperture size with superior EVM performance.

Performance analysis of pixelated antennas employing shifted cross‐shaped elements

AbstractThis article presents a detailed analysis of pixelated antennas employing shifted cross‐shaped elements optimised by evolutionary algorithms. Although, the size and number of the involved pixels, as well as the overall antenna size strongly influence performance of such antennas, detailed investigations on the interplay of geometrical considerations and their influence on parameters such as gain are missing from literature. Thus, the influence of various geometrical parameters on the performance of pixelated antennas for the first time, resulting in valuable design considerations is presented in this study. A maximum cross size could be found, for which an optimisation is viable. Based on this, a dataset consisting of 400 pixelated antennas was created, for different pixel‐ and antenna sizes and investigated certain parameters such as bandwidth and antenna gain. Most notably, a directly proportional dependence from the pixel‐on the antenna size for the optimisation of electrically large antennas was found. For small antennas, this dependency begins to deviate, leading to the fact that smaller pixels are needed to successfully optimise an antenna. Furthermore, the authors find that multi‐objective optimisation is a necessity to optimise matched antennas with a defined bandwidth and gain. The antenna gain shows a dependency on the cross size for electrically small antennas. From these results, design considerations for pixelated antennas can be derived. In addition to the extensive simulations, the dataset was verified in laboratory measurements.

High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors.

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO2 shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO2 coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.

Joint deconvolution and blind source separation with non-coplanar interferometric data

With the fastly increasing development of multichannel imagers, blind source separation (BSS) algorithms are ubiquitous in astrophysics to unmix multispectral images. In this context, analyzing data from the forthcoming very large, continental-size, radio interferometers using BSS algorithms raises two challenges. Firstly, the data are incomplete and deteriorated by instrumental effects, which requires incorporating a deconvolution step to retrieve exploitable images. Secondly, the data are affected by non-coplanar effects that notably arise from the very large antenna baselines and which must be accounted for in the separation scheme. For this purpose, we introduce a joint non-coplanar deconvolution and BSS algorithm, called wGMCA. The algorithm is tested and characterized in many challenging configurations, showing remarkable robustness to initialization and inversion. It is compared to classical methods that process the deconvolution and separation separately; these tests demonstrate the advantage of performing the deconvolution and separation in a single pass.

Suppressing grating lobes of large-aperture optical phased array with circular array design.

An optical phased array (OPA), especially a two-dimensional (2D) OPA, suffers from the trade-off among steering range, beam width, and the number of antennas. Aperiodic 2D array designs currently aimed to reduce the number of antennas and reduce grating lobes within a wide range fall short when an aperture approaches millimeter size. A circular OPA design is proposed to address this issue. The circular design substantially reduces the number of antennas while achieving the same wide steering range and narrow beam width of optimized aperiodic 2D OPA designs. Its efficient suppression of grating lobes, the key to a wide steering range with minimal number of antennas and large antenna spacing, is theoretically studied and validated by simulation. The novel, to the best of our knowledge, design allows less than 100 antennas, orders of magnitude reduction, for millimeter size aperture OPA designs. It paves the way for commercialization by significantly reducing control complexity and power consumption.

Active control of large space antenna truss structures using the equivalent beam model

Active control of large space antenna truss structures using the equivalent beam model

Process controlling iron-manganese regulation of the Southern Ocean biological carbon pump.

Iron (Fe) is a key limiting nutrient driving the biological carbon pump and is routinely represented in global ocean biogeochemical models. However, in the Southern Ocean, the potential role for other micronutrients has not received the same attention. For example, although manganese (Mn) is essential to photosynthetic oxygen production and combating oxidative stress, it is not included in ocean models and a clear understanding of its interaction with Fe in the region is lacking. This is especially important for the Southern Ocean because both Mn and Fe are strongly depleted. We use a hierarchical modelling approach to explore how the physiological traits associated with Fe and Mn contribute to driving the footprint of micronutrient stress across different phytoplankton functional types (PFTs). We find that PFT responses are driven by physiological traits associated with their physiological requirements and acclimation to environmental conditions. Southern Ocean-specific adaptations to prevailing low Fe, such as large photosynthetic antenna sizes, are of major significance for the regional biological carbon pump. Other traits more strongly linked to Mn, such as dealing with oxidative stress, may become more important under a changing Fe supply regime. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

A Massively Parallel Preconditioned FEM–BEM Method for Accurate Analysis of Complex Electromagnetic Field Problems

In this letter, a parallel preconditioned FEM-BEM method is presented for the solution of challenging electromagnetic (EM) field problems, especially for calculating the radiation characteristics of electrically large radome antenna systems. A preconditioner that combining the absorbing boundary condition (ABC) with the improved additive schwarz method is first proposed for the FEM-BEM system to improve the convergence. Then, an efficient parallel framework based on message passing interface (MPI) and open multi-processing (OpenMP) is designed to achieve massively distributed parallelization of the method. Numerical results demonstrate the benefits of the proposed preconditioner over traditional additive schwarz method, as well as the accuracy and parallel scalability of the implemented method. Finally, a complex EM system consisting of a waveguide slot antenna array and a dielectric radome with more than 127 medium wavelengths is simulated to verify the capability and effectiveness of the presented method.