Multiple-input And Multiple-output Antenna Research Articles

Broadband self-isolating MIMO antenna array for 6G IoT systems

A novel antenna array with improved radiation characteristics using a series-feed technique is presented in this article. The antenna array has a size of 132 × 80 μm and is developed using Polytetrafluoroethylene (PTFE) with graphene as conductive material. The proposed antenna comprises a central microstrip line loaded with short slant radiating stubs. The bandwidth characteristics of the antenna are enhanced by loading the slant stubs with octagonal ring elements. The number of radiating stubs is increased to enhance the overall radiation characteristics. The proposed THz antenna operates from 3.8 THz to 5.3 THz offering a fractional bandwidth of 31 % with reference |S11| ≤ −10 dB. In addition, a 1 × 2 antenna array with differential feeding is explored to improve the overall directionality of the antenna making it a viable solution for directional IoT systems. The estimated theoretical directivity is above 11 dBi and the total efficiency is greater than 75 % throughout the operating bandwidth. Furthermore, the multiple input and multiple output (MIMO) performance of the THz antenna is discussed. The proposed two-element has an intrinsic isolation of more than 40 dB. Owing to the enhanced bandwidth and radiation property, the proposed THz antenna is suitable for high data-rate 6 G Internet-of-things (IoT) communications.

A quad port dual band notch UWB MIMO antenna using hybrid decoupling structure

A four-port dual-band notch ultrawideband (UWB) multiple input and multiple output (MIMO) antenna for automotive applications is presented. Initially, a circular patch monopole antenna is designed and optimized by embedding a rectangular stub onto the radiator and lowering the ground plane to realize the UWB frequency spectrum. The dual-band frequency notch, from 4.6 to 5.9 and 6.8–8.8 GHz, is achieved using a half wavelength slot onto the feedline and a pair of H-shaped stubs across the feedline, respectively, to cover WLAN and complete x-band satellite communication. Further, the designed dual-band notch UWB antenna is transformed to a four-port MIMO antenna with interelement spacing much smaller than λ/4 (λ at 3.1 GHz) and a size of 0.46 × 0.41 × 0.01 λ3. Isolation improvement is achieved by a hybrid decoupling technique comprising a distinctive neutralization line (NL) and defected ground structure (DGS). The average isolation of the proposed design is better than 22 dB. Characteristic mode analysis of the proposed antenna is performed to analyze the specific significant mode and their contribution to the antenna radiation. The antenna design's diversity and time-domain properties are analyzed and found suitable for automotive applications. The antenna's electromagnetic interaction with the electrically large structure is studied by mounting the antenna onto an open-source automobile model, and the gain is determined to be more than 6.1 dB at the antenna's resonant frequencies.

Wideband Terminal Antenna System Based on Babinet's Principle for Sub-6 GHz and Wi-Fi 6E/7 Applications.

In this paper, a novel input impedance analysis methodology based on Babinet's principle to broaden bandwidth is proposed, and a broadband multiple-input and multiple-output (MIMO) antenna system is designed, fabricated, and measured for fifth-generation (5G) and Wireless Fidelity (Wi-Fi) 6E/7 mobile applications. By analyzing the input impedance of open-slot antennas and planar monopole antennas using numerical calculations, the characteristics of the input impedance can be obtained. We find that combining the two antenna types in parallel can significantly enhance the bandwidth. Then, the four-dimensional image calculated by MATLAB based on the parallel impedance formula is processed to validate the methodology. Thus, a broad antenna element based on the impedance property analysis methodology is achieved, which operates ranging from 2.6 GHz to 7.46 GHz. Moreover, the equivalent circuit of the antenna element is established to further verify the validity of the methodology. Finally, a broadband MIMO antenna system consisting of eight antenna elements is designed, fabricated, and measured, and the isolation performance is better than 12 dB. Acceptable total efficiency higher than 45% is also obtained with envelope correlation coefficients (ECCs) lower than 0.05. The proposed impedance property analysis methodology innovatively proposes a new way to increase bandwidth, which can be widely applied in various antenna designs. Also, reasonable results show that the proposed MIMO antenna system is a good candidate for 5G and Wi-Fi 6E/7 mobile applications.

Optimization Design of High-Dimensional Parameters MIMO Antenna in Semantic-Based Mobile Applications

To ensure the quality of semantic communication, an optimization scheme for multiple-input and multiple-output (MIMO) antenna design using in semantic-based mobile is proposed and verified. The scheme is based on a modified algorithm MOEA/D-BH, which integrates the black-hole (BH) algorithm into multi-objective EA based on decomposition (MOEA/D). By introducing controllable absorption distance and neighborhood learning mechanism, MOEA/D-BH can deal with high-dimension parameters well in a multi-objective optimization problem. Thus, in a limited design space, a satisfied antenna can be optimized by proposed scheme efficiently. This can be a feasible candidate scheme for MIMO antenna design. A single-band and dual-band MIMO antenna, which are applied for semantic-based mobile system, are optimized by proposed scheme sharing the same model. Both the data of simulation and measurement show good electrical and MIMO performances in the working frequency band. Thus not only the performance of the semantic communication definitely improved, but also it provides useful exploration for the development of intelligent semantic mobile systems.

A novel arc‐shaped four‐port wideband (21.8–29.1 GHz) MIMO antenna with improved characteristics for 5G NR networks

SummaryA novel antenna system that utilizes multiple‐input and multiple‐output (MIMO) technology to suit the requirements of 5G applications is proposed in this article. The antenna has a wide operating bandwidth and high isolation in n257/n258/n261 5G bands. The suggested arc‐shaped MIMO antenna is composed of four similar patch units with modified ground planes arranged in a four‐port configuration and is made on a Rogers RT/duroid 5880 substrate, which measures 31.891 × 37.5885 × 0.508 mm3. The prototype of the suggested MIMO antenna is realized to confirm the obtained simulated results and validate the proposed design. The four‐port MIMO antenna features a broad frequency range of 7.3 GHz from 21.8 to 29.1 GHz, a peak gain of 5.76 dBi at 29 GHz, and a good isolation less than −18 dB. The proposed antenna's MIMO performance is evaluated by analyzing several diversity parameters. The findings of the evaluation demonstrate an envelope correlation coefficient (ECC) value of less than 0.001, a diversity gain (DG) value exceeding 9.995 dB, and an average mean effective gain (MEG) of −3 dB within the operational frequency band. The suggested MIMO antenna's compact size and impressive performance make it a suitable choice for intended n257/n258/n261 5G NR networks.

A Compact MIMO Antenna Design Using the Wideband Ground-Radiation Technique for 5G Terminals

This paper introduces a 4 × 4 multiple-input and multiple-output (MIMO) antenna application based on the conception of the characteristic mode of 5G terminals. The proposed antenna used a series capacitor and a parallel capacitor to control input impedance matching, while the resonance frequency was controlled by employing a resonance loop capacitor. In this way, we achieved a compact miniaturization antenna that uses ground radiation for the target 5G New Radio (NR) operating bands with n48, n77, and n78 bands. The simulation and measurement data revealed that the –6 dB bandwidth of the proposed antenna was approximately 1,240 MHz (ranging from 3.14 GHz to 4.38 GHz), while the efficiency also improved from 38.7% (reference) to 49.1% (proposed) within the 3 GHz to 4.6 GHz range. Furthermore, the radiation pattern exhibited satisfactory radiation performance. Therefore, it was concluded that the proposed 4 × 4 MIMO antenna set technology has promising prospects for application in 5G communication terminals in the future.

ISOLATION ENHANCEMENT TECHNIQUES IN MIMO ANTENNA SYSTEMS: A SURVEY

In this survey paper, we discuss various techniques that can be employed to enhance isolation between multiple-input and multiple-output (MIMO) antennas. In this modern world, the MIMO antenna system is an important technique used in wireless technology. The channel capacity in a multipath environment can be improved by deploying multiple antenna elements, i.e., the MIMO technique at both the transmitter and receiver terminals. To have an efficient MIMO technique, the isolation between the multiple antenna elements must be as high as possible. In the past decade, many research works have proposed techniques to enhance isolation in MIMO antennas. In this survey, we examined various mutual coupling reduction techniques employed to improve isolation in multiple antenna elements and compared them based on various performance metrics. Isolation enhancement techniques such as stubs, filters, defected ground structure, decoupling networks, orientation of the radiating elements, parasitic elements, periodic structures, neutralization lines, metamaterials, etc., are discussed in this paper.

Design and analysis of ultra-wideband four-port MIMO antenna with DGS as decoupling structure for THz applications

The growing demand for high-speed communication has resulted in developing terahertz (THz) antennas that operate at high-frequency, high-speed, and high data rates. An ultra-broadband functioning four port THz multiple input and multiple output (MIMO) antenna with a defective ground plane as a decoupling structure is proposed in this study. A rectangular metallic patch was changed by integrating parasitic components onto the radiator with the lowered ground plane on a polyamide substrate to obtain the ultra wideband THz frequency operating antenna. The designed THz antenna has been transformed into a MIMO antenna by replicating horizontally and vertically with the separation of 0.08 λ and 0.01 λ, respectively (λ computed at 2 THz). The proposed THz MIMO antenna operates in the 2–10.7 THz frequency range and has an overall substrate dimension of 40 μm x 46 μm × 2 μm. The proposed antenna equivalent circuit is designed to validate the impedance bandwidth of the antenna. The designed THz MIMO antenna has isolation better than 20 dB across the impedance bandwidth. The isolation enhancement is achieved by creating alternate current channels through the defected ground structure of the antenna. The proposed THz MIMO antenna's MIMO diversity features are studied and determined to be ECC < 0.001, DG is about 10 dB, TARC < -10 dB, MEG < -3 dB, and CCL < 0.2 bps/Hz over the antenna's operational frequency.

High Performance Antenna System in MIMO Configuration for 5G Wireless Communications Over Sub‐6 GHz Spectrum

AbstractThis paper presents a high‐performance multiple input and multiple output (MIMO) antenna comprising 2 × 2 configuration of radiating elements that is designed for sub‐6 GHz applications. The proposed MIMO antenna employs four identical radiating elements. High isolation between the radiating elements and therefore reduced mutual coupling is achieved by spatially arranging the radiating elements in an orthogonal configuration. Also, a novel frequency selective surface (FSS) was employed to increase the gain of the MIMO antenna over a wide bandwidth from 3 to 6 GHz. This was achieved by locating the FSS above the antenna at a certain height. The FSS essentially enhanced the antenna's directivity, reduced back lobe radiation and mutual coupling. The antenna was fabricated on a standard Rogers RT Duroid 5880 dielectric substrate with a 0.8 mm thickness. The overall dimension of the MIMO antenna is 50 × 50 × 12.5 mm3 and it operates from 3.8 to 6 GHz, which corresponds to a fractional bandwidth of 41%. The proposed MIMO antenna has a measured peak gain of 4.8 dBi and inter radiation element isolation &gt;20 dB. Its envelope correlation coefficient is &lt;0.1 and diversity gain &gt;9.9 (dB). These characteristics make the proposed MIMO antenna system suitable for 5G communication systems.

Design of graphene-based multi-input multi-output antenna for 6G/IoT applications

In the future, 6G wireless communications will be integrated into various applications. It is expected that it will handle all Internet of Things services as well as satellite communications. Additionally, it is predicted to support machine learning (ML) and artificial intelligence (AI). So this work investigated four orthogonal ports graphene-based multiple-input and multiple-output (MIMO) antenna in the terahertz frequency regime. With wide-band (7.1-13) THz, minimum return loss close to -30 dB and a good isolation value. That was designed over silicon dioxide (Sio2) 100×100 substrate with a thickness of 10 µm and a maximum gain reaching 8.3 dB at 11 THz. By adjusting the provided DC voltage, the chemical potential of graphene can be tuned, which in turn allows for the MIMO antenna characteristics to be changed. Envelop correlation coefficient (ECC) and diversity gain (DG) were investigated for the presented design. In addition, these values were determined to assess compatibility and difficulties connected with communication over a short distance. The geometry of the MIMO antenna is adaptable to various applications in the THz band with highperformance requirements, such as sensing, scanning for security threats, biomedical applications, wireless communication systems with high speed built on the 6G standard, and the internet of things (IoT).

Characteristic-Mode-Analysis-Based Compact Vase-Shaped Two-Element UWB MIMO Antenna Using a Unique DGS for Wireless Communication

The modern electronic device antenna poses challenges regarding broader bandwidth and isolation due to its multiple features and seamless user experience. A compact vase-shaped two-port ultrawideband (UWB) antenna is presented in this work. A circular monopole antenna is modified by embedding the multiple curved segments onto the radiator and rectangular slotted ground plane to develop impedance matching in the broader bandwidth from 4 to 12.1 GHz. The UWB monopole antenna is recreated horizontally with a separation of less than a quarter wavelength of 0.13 λ (λ computed at 4 GHz) to create a UWB multiple input and multiple output (MIMO) antenna with a geometry of 20 × 29 × 1.6 mm3. The isolation in the UWB MIMO antenna is enhanced by inserting an inverted pendulum-shaped parasitic element on the ground plane. This modified ground plane acts as a decoupling structure and provides isolation below 21 dB across the 5–13.5 GHz operating frequency. The proposed UWB MIMO antenna’s significant modes and their contribution to antenna radiation are analyzed by characteristic mode analysis. Further, the proposed antenna is investigated for MIMO diversity features, and its values are found to be ECC &lt; 0.002, DG ≈ 10 dB, TARC &lt; −10 dB, CCL &lt; 0.3 bps/Hz, and MEG &lt; −3 dB. The proposed antenna’s time domain characteristics in different antenna orientations show a group delay of less than 1 ns and a fidelity factor larger than 0.9.

Design and analysis of Minkowski fractal antenna for wideband THz frequency tuning/multiband operation in a MIMO antenna system

The proposed Minkowski fractal antenna design achieves wideband and continuous frequency tuning in a multiple-input and multiple-output (MIMO) antenna system. By manipulating the fractal geometry of the unit antenna element, the resonance frequency of the antenna can be adjusted simply by changing its electrical length. The Minkowski fractal operator generates an increasing current path, resulting in a leftward frequency shift as the antenna side length increases with each iteration. In the first iteration, the proposed fractal antenna demonstrated a 97.9% continuous frequency shift from 0.204 to 0.404 THz with maximum return loss values of −31.23 and −21.6 dB, respectively. In the second iteration, a 38.6% continuous resonance frequency shift from 0.413 to 0.578 THz was achieved with return loss values of −18.22 and −40.47 dB, respectively. The maximum tunable bandwidths of the first and second iterations were approximately 0.2 and 0.16 THz, respectively. The proposed correlation between the dimensions of a single antenna and its resonance frequency provides the foundation for designing and implementing MIMO antenna systems in high-speed wireless devices, cognitive radio, and other multiband MIMO applications. A 2 × 2 MIMO antenna system has been designed from the results of the proposed single antenna to achieve multiband operation or frequency tuning through selective switching of the antenna feed.

Ultra Wideband (UWB) Multiple Input and Multiple Output (MIMO) Antenna Design : A Review

Since the Federal Communication Commission (FCC) issued a license for the 3.1 – 10.6 GHz frequency spectrum for unlicensed radio applications, many papers have been published regarding ultrawideband (UWB) antenna design. The issue of UWB antenna design is determining how to create an antenna with a wide bandwidth, capable of rejecting communication systems that coexist with UWB bands, and capable of designing UWB antennas for multiple input multiple output (MIMO) communication system applications. This study examines the design of UWB antennas with monopole and slot types based on evaluations published over the last two decades. The discussion began with UWB and MIMO systems and then moved on to the configuration of monopole and slot UWB antennas. UWB antenna layout with notched bands and the several types of notched bands available. Finally, two port and quad-port MIMO antenna configuration is examined. To further understand UWB antenna design, numerous UWB antenna configurations are simulated. The outcomes of this review can be utilized as preliminary reading material for researchers looking into UWB antennas.

A Compact Quad-Port UWB MIMO Antenna With Improved Isolation Using a Novel Mesh-Like Decoupling Structure and Unique DGS

The progress in mobile communication and the Internet of Things facilitates multiple features. The trending technology demands wider bandwidth so that user experiences uninterruptedly. The wider bandwidth and the isolation are two key characteristics of modern device antennas. The design of an ultrawideband (UWB) and four-port MIMO antenna is presented in this brief. The semicircular monopole patch is modified by including a guitar shape slot on a radiator and a half-circle slot in the lowered ground plane. The structural transformation affects the current path and enhances impedance matching, resulting in a broader bandwidth. The UWB monopole is replicated to construct a four-port multiple input and multiple output (MIMO) antenna. The separation between the interelement is less than the quarter wavelength. As a decoupling structure, the implicit mutual coupling in the MIMO elements is minimized by parasitic elements on the radiator and defected ground plane (DGS). A novel mesh-like structure embedded in radiating plane and DGS couples the current from an excited antenna and suppresses through the DGS correspondingly and improves the isolation. The overall geometry of the antenna is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$45 {\times } 45 {\times }1$ </tex-math></inline-formula> .6 mm3. The UWB MIMO has a measured impedance bandwidth of 113% between 4.5-16.4 GHz and greater than 20 dB of isolation throughout the bandwidth. Besides the mutual coupling reduction, radiation characteristics and all MIMO diversity parameters are studied. The performance of MIMO diversity characteristics is relatively good, with envelope correlation coefficient<0.002, diversity gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {\mathrm {\simeq }}10$ </tex-math></inline-formula> , mean effective gain<−3 dB, total active reflection coefficient<−10 dB, channel capacity loss <0.2 bps/Hz, and multiplexing efficiency<−0.5. The experimental and simulated findings are in line and make the projected design suitable for UWB MIMO applications.

Dual-Band MIMO Antenna with Enhanced Isolation for 5G NR Application.

A two-port multiple-input and multiple-output (MIMO) antenna with dual-band characteristics operating at the fifth-generation (5G) new radio (NR) sub-6 GHz n7/n38/n41/n79 bands is proposed. The proposed MIMO antenna is composed of two symmetric antenna elements and a defected ground plane. The antenna element consists of an incomplete circular patch with two L-shaped branches. By applying the defected ground structure and the slotted stub, the current distribution on the ground plane is changed to reduce the mutual coupling between the antenna elements. The measured -10 dB reflection coefficients cover 2.34-2.71 GHz and 3.72-5.10 GHz, while the measured isolation is larger than 20 dB at the whole operating frequency band. The paper has investigated different performance parameters in terms of the envelope correction coefficient (ECC), diversity gain (DG), radiation patterns, antenna gain, and efficiency. The proposed MIMO antenna is suitable for 5G applications.

Compact Wideband Self-Decoupled MIMO Antenna for 5G Communications.

A compact wideband self-decoupled multiple-input and multiple-output (MIMO) antenna is presented in this paper. The proposed antenna contains a pair of horizontal back-to-back elliptical tapered slots and a vertical elliptical tapered slot, which are etched on the circular metal patch. Based on characteristic mode analysis (CMA) and a suitable feeding structure, two desired characteristic modes (CMs) are excited. Therefore, across the entire matched bandwidth, a high level of isolation is realized without external decoupling structures. For validation, a prototype is fabricated and measured, and the measured results demonstrate that an impedance bandwidth of 3000 MHz with isolation higher than 20dB is achieved. Due to its self-decoupled property, high isolation, wide bandwidth, and compact size, the proposed antenna has excellent potential for 5G antenna array applications.

Dual‐port single‐loop MIMO antenna unit for unbroken metal‐frame terminals without cutting

AbstractIn this study, a simple and efficient dual‐port single‐loop antenna unit, intended for full metal‐frame terminals, is presented as the first of its kind. The proposed multiple‐input and multiple‐output (MIMO) antenna unit is constructed within a loop resonator, inserted between the metal frame and the ground plane without any slits or cuttings. Two voltage ports are utilized to simultaneously excite the shared loop resonator as radiators; however, the strong mutual coupling is induced from one port to another because of the shared loop resonator. Herein, a simple and efficient decoupling capacitor is loaded at the center of the loop resonator, decoupling and decorrelating the two‐port loop resonator. In this way, a dual‐port single‐loop antenna unit is accomplished for 5G MIMO applications. Two units are constructed, forming 4 × 4 MIMO antennas, which are validated in both simulation and measurement.

Investigations on Stub-Based UWB-MIMO Antennas to Enhance Isolation Using Characteristic Mode Analysis.

In this article, very compact 2 × 2 and 4 × 4 MIMO (Multiple-Input and Multiple output) antennas are designed with the help of Characteristics Mode Analysis to enhance isolation between the elements for UWB applications. The proposed antennas are designed with Characteristic Mode Analysis (CMA) to gain physical insight and also to analyze the dominant mode. To improve isolation and minimize the mutual coupling between radiating elements, elliptical shaped stubs are used. The dimensions of the 2 × 2 and 4 × 4 MIMO antennas are 0.29λ0 × 0.21λ0 (28 × 20 mm2) and 0.29λ0 × 0.42λ0 (28 × 40 mm2), respectively. These antennas cover the (3.1 GHz-13.75 GHz) UWB frequency band and maintain remarkable isolation of more than 25 dB for both 2 × 2 and 4 × 4 antennas. The impedance bandwidth of the proposed 4 × 4 MIMO antenna is 126.40% from 3.1 GHz to 13.75 GHz, including X-Band and ITU bands. The proposed 4 × 4 antenna has good radiation efficiency, with a value of more than 92.5%. The envelope correlation coefficient (ECC), diversity gain (DG), mean effective gain (MEG), and channel capacity loss (CCL) matrices of the 4 × 4 antenna are simulated and tested. The corresponding values are 0.0045, 9.982, -3.1 dB, and 0.39, respectively. The simulated results are validated with measured results and favorable agreements for both the 2 × 2 and 4 × 4 UWB-MIMO antennas.

Dual band 8 × 8 MIMO antenna system for DCS 1800 and 5G mobile applications

SummaryA dual‐band (1.6–1.9 GHz and 3.3–3.9 GHz) eight‐antenna multiple‐input and multiple‐output (MIMO) system is proposed in this paper. The basic structure of the proposed antenna element consists of microstrip lines, cylindrically shaped shorting, and a rectangular‐shaped defected ground structure (DGS). This structure is responsible for the production of a self‐ isolated MIMO system. The performance of the MIMO antenna system is investigated by the detailed analysis of S‐parameters, Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG), Total Active Reflection Coefficient (TARC), and Channel Capacity (CC). The proposed MIMO antenna system offers a good S‐parameter, radiation pattern, and satisfactory isolation characteristics. The MIMO antenna system is fabricated on lossy high dielectric ( = 4.3) FR4 substrate (loss tangent 0.02). The measured results are in good agreement with simulated one. The proposed antenna focuses on the 3.3–3.9 GHz frequency band, which covers bands 3.3–3.6 GHz (center frequency, 3.45 GHz) or 3.4–3.8 GHz (center frequency, 3.6 GHz) under the band below 6 GHz for 5G operation.

OTA Throughput Prediction of MIMO Antennas for Wireless Devices by Simulated Realistic Channel Model

A cost-effective and accurate method for predicting over-the-air (OTA) data throughput of multiple-input and multiple-output (MIMO) wireless devices in the antenna design stage is proposed. The method incorporates passive characteristics of MIMO antennas, realistic channel model, and conductive measurement results in a computer simulation framework. With extracted relation between received power and signal-to-noise ratio (SNR) of a wireless device at antenna ports by a conductive test and measured passive characteristics of MIMO antennas, OTA throughput versus received power in a realistic channel model is obtained by the Monte Carlo simulation of Shannon’s law. The unique features of this method include: no channel emulator equipment is required; a wide variety of precoding schemes can be applied; passive characteristics of antennas are fully incorporated; and frequency-selective fading channel can be adopted. The method has been intensively validated by comparing the calculated OTA throughputs with those measured by a multiprobe anechoic chamber method under spatial channel model extension (SCME) in three aspects: spatial correlation, radiation efficiency, and mutual coupling, showing as low as 0.2–0.3 dB discrepancy in power level in most cases. The method can be used to evaluate a MIMO array antenna design of a wireless device with respect to OTA performance.