Multiple-input Multiple-output Antenna Array Research Articles

A Low-Coupling Broadband MIMO Array Antenna Design for Ku-Band Based on Metamaterials

In response to the demand for broadband antennas in 5G mobile communications, this paper proposes a compact broadband multiple-input multiple-output (MIMO) antenna array. By chamfering a radiation patch and adding parasitic patches, the antenna is miniaturized while also expanding its bandwidth. The mutual coupling between the two antenna elements is reduced by loading a double-layer metamaterial decoupling structure above the elements which consists of an open resonating ring and a square ring. The antenna is simulated and measured using the three-dimensional electromagnetic simulation software HFSS and a vector network analyzer. The results show that the proposed antenna has a good radiation performance of <i>S</i><sub>11</sub> < -10 dB in the operating band of 12.11–13.99 GHz (relative bandwidth of 14.41%). Furthermore, the isolation of the proposed MIMO antenna array in the operating band is improved by more than -18.8 dB on loading the metameterial structure, indicating that the array antenna is suitable for use in the Ku-band.

High isolation MIMO antenna array for multiband terahertz applications

The advancement of future technology seeks to create wireless systems capable of achieving faster data transfer rates. One solution to confront this challenge is by employing Multiple-Input Multiple-Output (MIMO) systems. Nonetheless, the primary obstacle in assessing MIMO performance revolves around the size and spacing of the antennas to maintain isolation among the ports. Consequently, it is essential to devise an approach to tackle these challenges, with the utilization of a DGS as a viable and promising approach. Hence, in this study, we developed a dual-frequency MIMO system featuring two linear array antennas with two elements each and configured to function at 128 GHz and 178 GHz. Initially, this design is conceived as a single-element structure before evolving into a two-element MIMO antenna array configuration. The antenna's physical dimensions are 2.7 × 3.65 × 0.15 mm3, and it consists of two linear array nodes positioned at a separation distance of 0.18 mm. Additionally, the antenna delivers peak gains of 5.16 dB and 6.24 dB at frequencies of 128 GHz and 178 GHz, respectively. The values of various MIMO performance indicators meet stringent standards with ECC values below 0.012 and a DG of approximately 10 dB. Furthermore, the TARC remains below 0 dB. The aim of this research is to create a novel design for a THz antenna that can achieve a wide bandwidth and a high gain while maintaining the standard compact antenna size necessary for THz applications.

Highly isolated pin-loaded millimeter wave MIMO antenna array system for IoT-based smart environments

The Internet of Things (IoT) based wireless devices are mainly designed for rapid indoor millimeter-wave (mmW) communication systems. These systems often require high gain mmW antennas within a wideband MIMO framework. This work presents a high performance quad element pin-loaded multiple-input multiple-output (MIMO) antenna array for mmW communications that can be utilized within IoT-enabled smart environment. The novelty of these antenna elements lies in the incorporation of unique flower-shaped slots and shorting pins in each patch of a two-element antenna array. Moreover, a four-port MIMO antenna system is created by arranging the two element arrays in an orthogonal configuration. By employing this pattern diversity technique and incorporating shorting pins in each individual element, the adverse mutual coupling effects between adjacent elements are effectively mitigated. Experimental validation of the MIMO array prototype confirms the minimum isolation of 34 dB and high port isolation of 72 dB over the operating bandwidth from 26.31–30.25 GHz (3.96 GHz). Notably, these features together with lower correlation values and higher diversity gain, make it a good choice for mmW-based IoT devices in smart environments.

Broadband high gain performance MIMO antenna array for 5 G mm-wave applications-based gain prediction using machine learning approach

This paper presents the findings about implementing a machine learning (ML) technique to optimize the performance of 5 G mm wave applications utilizing multiple-input multiple-output (MIMO) antennas operating at the 28 GHz frequency band. This article examines various methodologies, including simulation, measurement, and the utilization of an RLC-equivalent circuit model, to evaluate the appropriateness of an antenna for its intended applications. In addition to its compact dimensions, the proposed design exhibits a maximum gain of 10.34 dBi, superior isolation exceeding 26 dB, and a broad bandwidth of 16.56 % Centered at 28 GHz and spanning from 25.905 to 30.544 GHz. Another supervised regression machine learning technique is utilized to predict the antenna's gain accurately. Machine learning (ML) models can be assessed by several measures, such as the variance score, R square, mean square error (MSE), mean absolute error (MAE), root mean square error (RMSE), and Mean Absolute Percentage Error (MAPE). Among the six machine learning models considered, it is seen that the Gaussian Process Regression (GPR) model exhibits the lowest error and achieves the highest level of accuracy in forecasting gain. The antenna under consideration has promising qualities for its intended use in high-band 5 G applications. This is evidenced by the modelling findings obtained from Computer Simulation Technology (CST) and Advanced Design System (ADS)and the measured and projected results derived using machine learning methodologies.

A quad-port triple-band high isolation terahertz MIMO antenna for short-distance THz communication links

This paper introduces an arrangement of a Multiple-Input Multiple-Output antenna array implemented specifically for operating within the THz frequency bands. The antenna is designed for short-distance THz communication links. A quad-port MIMO antenna configuration has been chosen to function across three frequency bands. Each cell element is situated on top of a silicon substrate. The combined cross-sectional surface of the MIMO antenna is 70 × 50 µm². The proposed MIMO antenna device reaches the following three frequency bands: 2.6–7.9 THz, 9.66–10.3 THz and 11.5–14.1 THz. In addition, the mutual coupling coefficient is less than − 20 dB, indicating strong isolation between antenna elements. This high isolation is obtained by using a defected sibstrat structure and a specifique distance between antenna elements. The MIMO array antenna attains peak gains of 11.88 dBi, 8.78 dBi and 10.65 dBi when operating over the three cited bandwidth. Furthermore, the suggested MIMO structure exhibits favorable characteristics with CCL < 0.5 bps/Hz/sec, MEG ≤ –3.0 dB, ECC < 0.01, and DG ≈ 10 dB, over the operating bands. Based on the results obtained and compared to several works reported in the literature, the proposed implementation maintains a good size-performance compromise which allows better adaptation to applications requiring versatile performance in various communication scenarios.

Design and Simulation of a High Performance 5G mm-Wave MIMO Antenna Array for Mobile Applications

This paper presents the design and simulation of an efficient multiple input multiple output (MIMO) antenna array for 5G millimeter-wave (mm-wave) mobile applications. With a dielectric constant of 2.2 and a loss tangent of 0.0009, the substrate employed is a Rogers RT5880 that is 0.254 mm thick. The 37 GHz frequency spectrum, reserved for millimeter-wave mobile applications for 5G, is covered by the proposed MIMO antenna arrays. The single antenna element has a gain of 6.44 dBi, which is increased to 7.89 dBi with a two-element array configuration and 10.88 dBi with a four-element array configuration. The proposed MIMO antenna array performance metrics—including reflection coefficient, VSWR, radiation efficiency, and gain—are seen and discovered to be below the accepted threshold. In the desired operating frequency band, it is noticed that more than 85% of the proposed MIMO antenna array's radiation efficiency is achieved. According to simulation findings, the proposed design may be potentially feasible for mobile applications using millimeter waves in the 5G network.

Physical layer security‐oriented energy‐efficient resource allocation and trajectory design for UAV jammer over 5G millimeter wave cognitive relay system

AbstractThis work focuses on the optimal trajectory of a rotary‐wing unmanned aerial vehicle (UAV) jammer and the system power allocation with the objective of maximizing the total secure energy efficiency (EE) of a slotted relay‐assisted millimeter wave (mm‐Wave) cognitive radio system. The UAV flies from starting location to final one in a round of communication mission that is overheard by a malicious eavesdropper. The network terminals are equipped with multiple‐input multiple‐output (MIMO) antenna array. This work first develops a practical approximation propagation model by addressing three key challenges: path loss, small‐scale Nakagami‐m fading channel gains, and transceiver antenna beamforming gains. By using the approximate model, the upper and lower bounds of the ergodic rate of each communication link are derived. Second, with the objective of maximizing secure EE, the optimal UAV trajectory and system resource allocation framework is established by considering the constraints of interference at primary receiver (PR), information‐causality relationship, rotary‐wing UAV propulsion energy and so forth. The optimal framework is solved with a tractable CVX tool by using the derived upper and lower bounds and successive convex approximation. Finally, an iterative optimizing algorithm is established by using Dinkelbach's method. In the simulation, the work presents the comparison of UAV trajectories, secure rates, and secure EEs of three schemes, that is, the proposed EE scheme, the non‐EE scheme where only the optimal secure rate is considered, and the EE scheme with the consideration of all communication‐related energy consumption. The simulations show that the EE schemes achieve smoother UAV trajectory than non‐EE, but the non‐EE scheme has higher secure rate. The impact of communication energy consumption is negligible. In addition, the effect of MIMO antenna array and mm‐Wave on system performance is exploited.

Machine learning with A MIMO Antenna for Wireless Communication Systems

Multiple-input multiple-output (MIMO) antenna is a technology that uses multiple antennas at both the transmitter and receiver to improve the performance of wireless communication systems. One of the challenges in designing MIMO antennas is to reduce the complexity of the antenna array, while still maintaining good performance. One way to reduce complexity is to use shared antennas. Shared antennas are antennas that are used by multiple elements of the MIMO array. This can reduce the number of required antennas and simplify the design of the antenna array. The B-shape of the MIMO antenna by using CST program can also be used to reduce complexity. For example, hexagonal MIMO antennas have been shown to have good performance and can be implemented with a simple design. Additionally, the use of defected ground planes (DGPs) can be used to improve the isolation between the elements of a MIMO antenna array, which can also reduce complexity. The design of MIMO antennas is a complex and challenging task. However, by using shared antennas and other design techniques and AI, it is possible to reduce the complexity of MIMO antennas while still maintaining good performance.

An Eight-Element MIMO Antenna Array for NR Application

We propose an eight-element multiple-input multiple-output (MIMO) antenna array for 5G (fifth generation) New Radio (NR) applications in the n78 (3.3–3.8 GHz) band to achieve a high data rate. In the proposed work antenna elements have rectangular slots on the ground. Microstrip lines directly feed an open slot in this design. The dimensions of the open slot are 21.5 × 4 mm (0.24 λ × 0.046 λ at 3.5 GHz) and the slot covers 19.18% of the bandwidth in the frequency band 3.3–4 GHz. The eight antenna elements are arranged in such a way that they are coupled and also achieve an excellent degree of polarization. The proposed eight-element MIMO antenna array is fabricated and measured. Across the operation band, the measured isolation of the proposed antenna is −35 dB, −18 dB, −11 dB, −50 dB, −18 dB, −30db, −11 dB, and −35 dB for S12, S15, S26, S34, S53, S56, S64, and S78 respectively. The proposed antenna design can achieve desired antenna parameters, i.e. Isolation >11 dB, total efficiency >68%, and several MIMO performance characteristics are evaluated, including envelope correlation coefficient (ECC) < 0.03, the total active reflection coefficient (TARC) is −7 dB, the diversity gain (DG) is 9.96 dB and the channel capacity losses (CCL) is less than 0.02 were measured at desired bandwidth. The radiation pattern and antenna gain are also shown in this paper. The design is suitable for 5G communication networks.

A Compact Wideband (22–44GHz) Printed 2×4 MIMO Array Antenna with High Gain for 26/28/38GHz Millimeter-Wave 5G Applications

In this work, a novel multiple input multiple output (MIMO) array antenna system with a large bandwidth and high gain has been simulated, analyzed, fabricated, and measured. The proposed antenna is structured in [Formula: see text] patch configuration along with a cross shaped ground plane loaded with four square and one circular shaped defect. The projected antenna occupies a total size of [Formula: see text]. Several slots in an elliptic form have been added to the patches to achieve the required results in terms of wide bandwidth and high gain. The MIMO antenna array is fabricated and experimentally tested to confirm the simulation results. The suggested MIMO array antenna offers an impedance bandwidth of 22[Formula: see text]GHz covering 22–44[Formula: see text]GHz wide range of frequencies with a high peak gain of 17[Formula: see text]dBi at 38[Formula: see text]GHz. The designed MIMO antenna offers superior diversity performance and it supports several 5G NR bands n257/n258/n259/n260/n261 in the mm-wave spectrum. The suggested MIMO antenna supports 5G application bands that are deployed in UK, USA, China, Europe, Canada, India, and Europe.

Maximum Exposure Evaluation for MIMO Based on Optimization Algorithm

IEC/IEEE FDIS 63195-2 requires the maximum exposure evaluation to determine if the product meets the radiation limit requirements specified by ICNIRP. The miniaturization and integration of millimeter wave antennas make it possible to deploy antenna arrays supporting Multiple-Input Multiple-Output (MIMO) technology in mobile terminals, which brings challenges to traditional exposure compliance testing. This is caused by the complex electromagnetic environment generated around the equipment by beam focusing technology and the difficulty in determining the maximum exposure of electromagnetic exposure dose by traditional measurement methods. However, mathematical model-based evaluation methods may produce overly conservative results, limiting the maximum allowable transmit power of 5G devices and resulting in wasted system performance. In this study, we take advantage of the optimization algorithm in searching for globally optimal solutions under multivariate constraints, and its search strategy is improved to evaluate the largest exposure of millimeter wave MIMO antenna arrays in the target region.

Isolation Improvement Using the Field-Circuit Combined Method for In-Band Full-Duplex MIMO Antenna Arrays

This paper proposes a field-circuit combined decoupling method for co-polarized in-band full-duplex multiple-input multiple-output (MIMO) antenna arrays. The proposed field-circuit combined method is composed of decoupling network and neutralization-based decoupling. An in-band full-duplex antenna with high isolation and low cross-polarization level is designed and extended to a 1 × 4 linear array. The decoupling network and ADS are applied for the array to alleviate the mutual coupling by rebuilding the neutralization wave paths in the circuit and field domains. Thus, low coupling (&lt; −25 dB) among the transmitting/receiving antennas and high isolation (&gt; 47 dB) between the transmitting and receiving antennas are achieved at 2.6 GHz, exhibiting a superior decoupling performance.

Aperture Reduction Using Downward and Upward Bending Arms for Dual-Polarized Quadruple-Folded-Dipole Antennas

A method to miniaturize the aperture of a dual-polarized quadruple-folded-dipole (QFD) antenna by bending its arms downward or upward is proposed in this letter. Two practical prototypes called downward-bending-arm (DBA) antenna and upward-bending-arm (UBA) antenna are presented and elaborated. Both the DBA and UBA antennas have four pairs of arms bent downward or upward along the four edges of the planar QFDs, respectively, which enable the aperture of the DBA and UBA antennas to shrink to around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.24{\lambda }_0 \times 0.24{\lambda }_0$</tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\rm{\lambda }}}_{0}$</tex-math></inline-formula> is the free-space wavelength at 2 GHz). Both antennas can achieve relatively small apertures while ensuring good matching, isolation, and radiation performances within the band of interest. Especially, the DBA antenna has a lower profile than the UBA antenna while the UBA antenna outperforms the DBA antenna in realized gain by approximately 1 dB. Meanwhile, the UBA antenna has narrower half-power beam width, which will be beneficial in compact massive multiple-input–multiple-output antenna arrays for improved radiation patterns.

Eight-Port Modified E-Slot MIMO Antenna Array with Enhanced Isolation for 5G Mobile Phone

An eight-element antenna system operating at sub 6 GHz is presented in this work for a future multiple-input multiple-output (MIMO) system based on a modified E-slot on the ground. The modified E-slot significantly lowers the coupling among the antenna components by suppressing the ground current effect. The design concept is validated by accurately measuring and carefully fabricating an eight-element MIMO antenna. The experimentation yields higher element isolation greater than −21 dB in the 3.5 GHz band and the desired band is achieved at −6 dB impedance bandwidth. The E-shape slot occupies an area of 17.8 mm × 5.6 mm designed on an FR-4 substrate with dimensions of 150 mm × 75 mm × 0.8 mm. We fed the I-antenna element with an L-shape micro-strip feedline, the size of the I-antenna is 20.4 × 5.2 mm2, which operates in the (3.4–3.65 GHz) band. Moreover, our method obtained an envelope correlation coefficient (ECC) of &lt;0.01 and an ergodic channel capacity of 43.50 bps/Hz. The ECC and ergodic channel capacity are important metrics for evaluating MIMO system performance. Results indicate that the proposed antenna system is a good option to be used in 5G mobile phone applications.

Ultra-Massive MIMO Channel Measurements at 5.3 GHz and a General 6G Channel Model

Ultra-massive multiple-input multiple-output (MIMO) technology will bring unique channel characteristics that need to be fully explored through channel measurements and channel modeling. In this paper, single-user and multi-user channel measurements using ultra-massive MIMO antenna arrays with different configurations are conducted at 5.3 GHz band. The non-stationarity, spherical wavefront, channel hardening, and sparse properties are validated by the channel measurements. Correspondingly, a general three-dimensional (3D) sixth generation (6G) non-stationary geometry-based stochastic model (GBSM) for ultra-massive MIMO communication systems is proposed. The statistical properties of channel measurements and the corresponding channel model are studied, including delay power spectral density (PSD), angular PSD, spatial cross-correlation function (SCCF), normalized user-side correlation matrix, singular value spread (SVS), degrees of freedom (DoF), and diversity level. In addition, channel capacities of channel measurements and the corresponding channel model are studied. The accuracy of the proposed general channel model is validated by the consistency of simulation results and measurement results, which indicates that the proposed model can be applied to ultra-massive MIMO communication systems.

A Wideband Eight-Element MIMO Antenna Array in 5G NR n77/78/79 and WLAN-5GHz Bands for 5G Smartphone Applications

In this paper, a wideband eight-element multiple-input multiple-output (MIMO) antenna array for 5G smartphone applications is presented. Each antenna is composed of a dual-arm tortuous monopole radiating element with a double-stub tuner and an open slot on the ground plane. Tuning stub microstrip lines are utilized to improve impedance matching. The operating bandwidth of the single antenna element is from 3200 to 6000 MHz with three resonant frequencies. The operating bandwidth covers the 5G new radio (NR) bands (n77/n78/n79) and the WLAN-5GHz band. The isolation of the proposed MIMO antenna array is above 10 dB in the entire operating band without any isolation elements. Furthermore, the proposed MIMO array was manufactured and measured. The measured results validate that the MIMO antenna array has a wide 6-dB impedance bandwidth from 3.2 to 6 GHz and the isolations are all more than 10 dB. The total efficiency ranges from 38% to 83%. The above results show that this MIMO antenna array can support 5G applications in smartphones.

Robust Beam Management in Position and Velocity Aware V2V Communications Using Distributed Antenna Subarrays

Millimeter-wave vehicle-to-vehicle communication systems with multiple-input multiple-output antenna array have drawn significant attention because it is expected to satisfy the growing bandwidth requirements for the cooperative intelligent transportation systems. However, maintaining high-quality communication links between communicating vehicles without high overhead is a challenging problem due to the high mobility of vehicles. In this paper, we propose a beam management algorithm with spatially distributed antenna subarrays instead of a single co-located antenna array. Unlike existing methods, we use distributed antenna subarrays to exploit the geometric relationship of the beam directions and the relative distance between communicating vehicles. We reduce the beam alignment errors by minimizing the sum of squared errors between the estimated beam direction after the beam training process and the refined beam direction derived from the measured position and velocity data. Additionally, a position data request protocol is devised to reduce the beam refining errors. Numerical results demonstrate that the proposed beam management algorithm successfully reduces the beam alignment errors and it is robust to position and velocity measurement errors.

RETRACTED ARTICLE: Design and analysis of MIMO system for THz communication using terahertz patch antenna array based on photonic crystals with graphene

In this paper, a novel multiple input/multiple output (MIMO) antenna system with a graphene-based patch antenna array for THz communications channel capacity enhancement has been proposed and investigated. Systematic analysis has been conducted on the graphene load conductivity by determining the operating modes related to its chemical potential. Further, the projected MIMO antenna arrays have been designed with three different approaches such as homogeneous, photonic crystals, and optimized photonic crystals. The targeted MIMO antenna arrays have been compared with their radiation characteristics such as return loss, bandwidth, and gain. The obtained results in CST simulations of the proposed graphene-based 1×2 patch antenna array using the optimized photonic crystals substrate exhibited excellent performance improvements as compared to the homogeneous substrate and the photonic crystals substrate around 0.65 THz, which achieved a peak gain of 11.80 dB and broad bandwidth greater than 614 GHz. Next, The 2×2 MIMO system scenario was studied and analyzed using the mentioned targeted MIMO antenna arrays by calculating the total path loss and the channel capacity. The obtained results showed that the proposed 2×2 MIMO system with the MIMO antenna array based on the optimized photonic crystals substrate achieved the highest capacity and the lowest total loss compared to a simple MIMO antenna array based on a homogeneous substrate. The capacity was calculated as 23.64 bit/s/Hz, and this was a remarkable enhancement compared with previously reported studies. In addition, this capacity was investigated further for different system configurations and different spacings between the transmission and receiver antennas.

Integrated dual‐band multiple‐input multiple‐output antenna module using higher mode control for 5G applications

This study presents a self-decoupled and highly integrated multiple-input multiple-output (MIMO) antenna pair for the 3.5 GHz (3.4–3.6 GHz) and 5 GHz (4.8–5 GHz) frequency bands, where a loop-type antenna and a dipole-type antenna are assembled into the front and backside of a compact modular board. A tuning inductor and a tuning capacitor are employed in the loop-type antenna and the dipole-type antenna, respectively, for higher mode resonance control, such that the dominant mode and higher mode of each antenna element are excited to achieve dual-band operation. Herein, the dominant modes of the loop-type antenna and the dipole-type antenna are orthogonal to each other, contributing to the self-decoupling effect in the lower band. Otherwise, the modal orthogonality of the higher modes of the two antennas is responsible for the high-isolated performance of the higher band. In this way, the proposed dual-band MIMO antenna module obtains a high spatial utilization ratio, even though they are disposed of in the same volume. The MIMO antenna module can produce impedance bandwidths above 200 MHz at both frequency bands, and the isolation within the lower and higher bands is above 16.5 and 13.5 dB, respectively. Additionally, an 8 × 8 MIMO antenna array is further constructed and measured. In measurement, the total efficiencies are higher than 60%, and the envelope correlation coefficient values are all below 0.1. Therefore, it is demonstrated that the proposed technique can be promisingly applied in large-scale MIMO antenna systems for current and future terminal devices, having advantages in multiband operation, high integration, and inherent isolation.

Miniaturized MIMO Antenna Array with High Isolation for 5G Metal-Frame Smartphone Application.

In this paper, a highly isolated multiple-input multiple-output (MIMO) antenna array is proposed for fifth-generation (5G) metal frame smartphones. The eight identical small-sized inverted F-shaped folded slots are etched on the metal frame as a MIMO antenna. The bandwidth of the antenna can be adjusted by changing one of the short branches of the antenna. The bandwidth of the antenna can reach the N79 band (4.4~5.0 GHz). By carefully arranging the positions of the eight antenna elements, ideal spatial diversity can be successfully achieved to mitigate the coupling between the antenna elements effectively. What is more, a small combination slot of C-shape (0.0078 × 0.047λ2) and vertical I-shape (0.12 × 0.004λ2) between each antenna element is introduced to improve the element isolation of the MIMO antenna system. The proposed MIMO array has been simulated, fabricated, and measured. The results show good impedance matching (return loss > 6 dB) and high isolation (>22 dB). Due to the decent element isolation, the envelope correlation coefficient (ECC) between each antenna element is below 0.049. It can provide a reliable anti-interference performance for the MIMO antenna system. In addition, the measured radiation efficiencies of the MIMO antenna system are higher than 50%. The interaction of the hand model with the MIMO antenna system is also investigated, including the specific absorption rate (SAR).