Multiple-input Multiple-output Antenna Design Research Articles

Advancements in MIMO Antennas for Enhanced Performance in 5G Smartphones Communication

In this review paper provides a comprehensive overview of recent advancements in multiple input multiple output (MIMO) antenna designs for 5G smartphones. There are various antenna configurations that are discussed along with benefit and limitations. The paper also examines key challenges such as antenna mutual coupling, isolation and the size constraints inherent in smartphones. Furthermore, the impact of MIMO antenna design on 5G smartphone performance characteristics such as gain, radiation efficiency and spatial multiplexing capability is also analyzed. Finally, future research directions and potential innovations in MIMO antenna technology for 5G smartphones are identified to address emerging requirements and opportunities in next-generation wireless communication systems. The comprehensive comparison of different MIMO antenna performance is also given.

Low mutual-coupling MIMO antenna using dielectric resonators

This paper presents a design for a low-coupling multiple-input multiple-output (MIMO) antenna with two antenna elements. There is a dielectric resonator centrally and four inverted-F slots around on each element. This dielectric resonator consists of a dielectric block with an I-shaped metal pattern and is encircled by a metal ring with air holes. The use of inverted-F slots and the dielectric resonator effectively reduces the mutual coupling between the two antenna elements. Simulation and measurement results indicate that the designed MIMO antenna achieves a high level of isolation, maintains a low envelope correlation coefficient, and possesses a relatively high overall active reflection coefficient efficiency within the bandwidth of 6.41 GHz–6.62 GHz. These characteristics make the MIMO antenna perform exceptionally well in enhancing communication system performance, particularly in terms of signal quality, channel capacity, and system efficiency.

Enhancing Diversity and Isolation Performance for a Four-Port Mimo Antenna in FR-1 5G Frequency Bands

The paper aims to improve the diversity parameters and isolation of a four-port Multiple-Input Multiple Output (MIMO) antenna configured as 4 × 1 for the 5G-NR FR-1 N78/77/48 band. The 4-port MIMO design entails the incorporation of dual sets of monopole antennas. Each pair of monopoles in this configuration arranges the second monopole to mirror the first one within its set. The MIMO antenna design incorporates Rogers RO3003 substrates with a ϵr of 3.2. The antenna size is compact, with dimensions of 34 × 129.5 × 1.6 mm3. The design of the four-port MIMO antenna introduced parasitic decoupling elements between the antennas, a defected ground structure (a T-shaped stub), and the incorporation of a grounding branch on the ground plane. These measures effectively mitigate the coupling between the antennas. The antenna functions within the frequency range of 2.25 GHz to 4.25 GHz, offering a bandwidth of 2 GHz with a peak gain of 4.0 dBi at 3.52 GHz. The diversity performance of the suggested MIMO antenna is evaluated using the parameters TARC, E.C.C., D.G., CCD/CCL, and M.E.G. The values obtained are as follows: starting from −15 dB, 0.0408, 9.989 dB, 0.08 bits/s/Hz, and 0.48 dB, respectively. According to both simulated and measured data, the MIM0 antenna system design presents good isolation capabilities, excellent diversity performance, and robust impedance matching. This can be a good option for FR-1 5G-NR N78/77/48 band communication.

Compact body‐worn MIMO antenna with high port isolation for UWB applications

SummaryThis article investigates the mutual coupling reduction of a compact two elements wearable ultra‐wideband (UWB) multiple‐input multiple‐output (MIMO) antenna. The ground plane of the proposed wearable MIMO antenna structure consists of three connected square ring‐shaped stubs and two rectangular slots of narrow height. These ground stubs and slots minimize the mutual coupling effect between antennas and provide high isolation. The suggested MIMO antenna functions from the 1.87 to 13.82 GHz frequency spectrum covering WLAN (2.4–2.484 GHz), UWB (3.1–10.6 GHz), and X band (8–12 GHz) with 152.32% fractional bandwidth. It sustains port isolation above 27 dB throughout the 2 to 13.82 GHz frequency band. Inside the whole working frequency band, the suggested antenna offers a tiny envelope correlation coefficient (ECC < 0.098), greater diversity gain (DG > 9.93 dB), minimum channel capacity loss (CCL < 0.32 bits/s/Hz), and slight magnitude variation in mean effective gain of antenna ports (< 0.1 dB). The recommended antenna yields a SAR level below the designated threshold (<1.6 W/kg), affirming its suitability for body‐worn applications. The designed MIMO antenna structure has an overall volume of 32 × 48 × 1.5 mm3.

Isolation enhancement of distinct element dual polarized compact MIMO antenna for 5G/WLAN application

AbstractA novel‐shaped dual‐polarized low‐profile multiple‐input multiple‐output (MIMO) antenna with high isolation is proposed for 5G/WLAN application. An 8‐element MIMO antenna design comprises two unique planar radiators (chamfer, circular). Each radiator has dual feed and dual polarization characteristics. The prototype is fabricated with an FR‐4 dielectric substrate. A decoupling structure maintains desirable isolation for self‐isolated elements (−12 dB) using substrate integrated waveguide stubs between inter‐ports and high isolation among the adjacent radiating elements (−15 dB). The simulation was performed by using CST microwave studio. The simulated results of the proposed MIMO antenna are compared with the measurement results. Furthermore, ECC and DG are investigated.

Design and optimization of metamaterial-based highly-isolated MIMO antenna with high gain and beam tilting ability for 5G millimeter wave applications

This paper presents a wideband multiple-input multiple-output (MIMO) antenna with high gain and isolation, as well as beam tilting capability, for 5G millimeter wave (MMW) applications. A single bow-tie antenna fed by a substrate-integrated waveguide (SIW) is proposed to cover the 28 GHz band (26.5–29.5 GHz) with a maximum gain of 6.35 dB. To enhance the gain, H-shaped metamaterial (MM)-based components are incorporated into the antenna substrate. The trust-region (TR) gradient-based search algorithm is employed to optimize the H-shape dimensions and to achieve a maximum gain of 11.2 dB at 29.2 GHz. The MM structure offers zero index refraction at the desired range. Subsequently, the MIMO system is constructed with two vertically arranged radiators. Another MM, a modified square resonator (MSR), is embedded between the two radiators to reduce the mutual coupling and to tilt the antenna main beam. Herein, the TR algorithm is again used to optimize the MSR dimensions, and to enhance the isolation to a maximum of 75 dB at 28.6 GHz. Further, the MSR can tilt the E-plane radiation by ± 20° with respect to the end-fire direction when alternating between the two ports' excitation. The developed system is validated experimentally with a good matching between the simulated and measured data.

A flexible CPW-fed tri-band four-port MIMO antenna for 5G/WIFI 6E wearable applications

This paper introduces a novel flexible tri-band four-port Multiple Input Multiple Output (MIMO) antenna with coplanar waveguide (CPW)-fed for modern 5G/WIFI 6E wearable applications. The proposed antenna operates in three frequency bands by using an etching of rectangular monopole with inverted U-shape slot and a L-shape branch. The prototype of the design is manufactured on flexible Liquid crystal polymer (LCP) substrate with a miniature size of 56 mm × 56 mm × 0.1 mm. The presented antenna operating bands are 2.54–3.56 GHz, 4.28–4.97 GHz and 5.37–8.85 GHz, which can cover Chinese 5G standards n78 (3.4–3.5 GHz), n79 (4.8–4.9 GHz) and WIFI 6E (5.945–7.125 GHz) band. The isolation of the MIMO antenna is higher than 20 dB over whole operating bands by loading a crossed branch with two circular rings. Moreover, the significant performance parameters of the designed MIMO antenna are evaluated, including gain, efficiency, radiation pattern, ECC, DG and TARC. At the same time, the bending test and human test of the flexible antenna are studied in this article. All simulate and measured results demonstrate that the designed tri-band four-port MIMO antenna is promising for 5G/WIFI 6E wearable applications.

Using Loaded N-Port Structures to Achieve the Continuous-Space Electromagnetic Channel Capacity Bound

A method for achieving the continuous-space electromagnetic channel capacity bound using loaded <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -port structures is described. It is relevant for the design of compact multiple-input multiple-output (MIMO) antennas that can achieve channel capacity bounds when constrained by size. The method is not restricted to a specific antenna configuration and a closed-form expression for the channel capacity limits are provided with various constraints. Furthermore, using loaded <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -port structures to represent arbitrary antenna geometries, an efficient optimization approach is proposed for finding the optimal MIMO antenna design that achieves the channel capacity bounds. Simulation results of the channel capacity bounds achieved using our MIMO antenna design with one square wavelength size are provided. These show that at least 18 ports can be supported in one square wavelength and achieve the continuous-space electromagnetic channel capacity bound. The results demonstrate that our method can link continuous-space electromagnetic channel capacity bounds to MIMO antenna design.

A Novel Densely Packed 4 × 4 MIMO Antenna Design for UWB Wireless Applications.

In this article, a compact 4-port UWB (Ultra-Wide Band) MIMO (Multiple Input Multiple Output) antenna is proposed. A low profile FR-4 substrate is used as a dielectric material with the dimensions of 58 × 58 mm2 (0.52λ × 0.52λ) at 2.8 GHz and a standard thickness of 1.6 mm. The proposed design characterizes an impedance bandwidth starting from 2.8 to 12.1 GHz (124.1%). Each of the four elements of the proposed MIMO antenna configuration consists of a monopole antenna with PG (partial ground) that has a slot at its center. The corner of each patch (radiator) and ground slot are rounded for impedance matching. Each unit cell is in an orthogonal orientation, forming a quad-port MIMO antenna system. For reference, the partial ground of each unit cell is connected meticulously with the others. The simulated results of the proposed quad-port MIMO antenna design were configured and validated by fabrication and testing. The proposed Quad-port MIMO design has a 6.57 dBi peak gain and 97% radiation efficiency. The proposed design has good isolation below 15 dB in the lower frequency range and below 20 dB in the higher frequency range. The design has a measured ECC (Envelop Correlation Co-efficient) of 0.03 and DG (Diversity Gain) of 10 dB. The value of TARC (Total Active Reflection Coefficient) over the entire operating band is less than 10 dB. Moreover, the design maintained CCL (Channel Capacity Loss) < 0.4 bits/sec/Hz and MEG (Mean Effective Gain) < 3 dB. Based on the obtained results, the proposed design is suitable for the intended high data rate UWB wireless communication portable devices.

Design of UWB MIMO antenna using lean wearable textile substrate for reduced SAR

PurposeThis paper aims to propose a two-element dual fed ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with no additional decoupling structures. The antenna operates from 3.1 to 10.6 GHz. The antenna finds its usage in on-body wearable device applications.Design/methodology/approachThe antenna system measures 63.80 × 29.80 × 0.7 mm. The antenna radiating element is designed by using a modified dumbbell-shaped structure. Jean cloth material is used as substrate. The isolation improvement is achieved through spacing between two elements.FindingsThe proposed antenna has a very low mutual coupling of S21 < −20 dB and impedance matching of S11 < −10 dB. The radiation characteristics are stable in the antenna operating region. It provides as ECC < 0.01, diversity gain >9.9 dB. The antenna offers low average specific absorption rate (SAR) of 0.169 W/kg. The simulated and measured results are found to be in reasonable match.Originality/valueThe MIMO antenna is proposed for on-body communication, hence, a very thin jean cloth material is used as substrate. This negates the necessity of additional material usage in antenna design and the result range indicates good diversity performance and with a low SAR of 0.169 W/kg for on-body performance. This makes it a suitable candidate for textile antenna application.

A Conformal Dual-Band CPW-MIMO Antenna for 5G-V2X Communication

A Co-Planar Waveguide (CPW) fed conformal Multiple Input Multiple Output (MIMO) antenna is presented by deploying circular and rectangular patch in a stacked configuration. The analytical equations for the antenna are modeled and compared with the proposed antenna. The antenna is designed on a flexible polyimide substrate featuring a dielectric value of 3.5 with 0.1 mm thickness resonating at two frequencies, LTE-42 Band (5G-V2X) 3.4-3.6 GHz and Dedicated Short Range Communication (DSRC) 5.850-5.925 GHz. The design is further extended as a 4 × 4 MIMO structure by positioning the antenna elements orthogonal, separated by a distance of 10 mm. The antenna exhibits a reflection coefficient < −10 dB with a gain value between 4.5 and 5.25 dB over the desired frequencies. The radiation efficiency of the antenna is around 90% at both bands. MIMO parameters were measured to analyze the MIMO performance of the proposed antenna and the placement analysis of the antenna is studied by mounting the antenna on various vehicle positions and their corresponding pattern were characterized. The designed MIMO antenna is fabricated and tested, having an overall size of 85 × 85 × 0.1 mm3, offering extremely flexible design functioning to be a promising candidate for next-generation V2X Communication.

A High-Frequency Planar-Configured Millimeter-Wave MIMO Antenna for Fifth-Generation NR Operations

This article presents a simple planar millimeter-wave (mm-wave) multiple input multiple output (MIMO) antenna with four closely spaced radiating elements. The antenna is intended to enhance the bandwidth for 5G new radio (NR) applications and also cover the industrial Ka-band (26.5-40 GHz), Q-band (30-50 GHz), and U-band (40-60 GHz) frequency ranges. The antenna is designed using Rogers RT/duroid 5880 substrate with a size of 25 × 26 × 1.6 mm3. The proposed antenna consists of four identical radiating elements with two of them positioned in a linear configuration facing each other, while the other two elements are placed opposite to the first two, which improves isolation between the elements. Across the entire operating frequency range (26-60 GHz), the antenna demonstrated excellent performance, including 34 GHz wide bandwidth, high isolation of &gt;25 dB, nearly omnidirectional radiation patterns, high gain of 11.1 dB with a high radiation efficiency of 94%, low envelope correlation coefficient (ECC) of 0.0068, and high diversity gain (DG) of 9.967 dB. The simulated findings exhibit a strong positive correlation with the experimental results. The proposed MIMO antenna design is a promising solution for 5G NR applications.

High isolation frequency-reconfigurable UWB-MIMO antenna with on-demand WiMAX band elimination

Abstract In this article, a planar dual-element frequency reconfigurable multiple-input multiple-output (MIMO) antenna for ultra-wideband (UWB) applications is studied. The frequency band can be switched between UWB operation and single band rejected UWB performance using a pair of PIN diodes in the MIMO configuration. The presented antenna is comprised of two similar slotted circular radiators, having tapered microstrip feedlines and separate partial ground planes. An RT/Duroid 5880 substrate with size 54 × 54 mm2 is used for the design purpose. Rotational symmetry between the radiators and diagonally oriented t-shaped decoupling structure behind the substrate have been utilized for high isolation purpose. The designed MIMO antenna exhibits UWB performance in mode 1. In other mode, the antenna operates in the frequency range 2.46–10.44 GHz with Worldwide Interoperability for Microwave Access (WiMAX) band rejection. Thus, the MIMO antenna exhibits on-demand single band rejection behavior depending on the switching conditions of the diodes. The measured isolation is greater than −20 dB in both the modes. The presented MIMO configuration possesses compact and planar geometry with high gain, good isolation, ultrawideband performance with reconfigurable band elimination, high efficiency and efficient diversity performance parameters. The suggested antenna is a good choice to be utilized for portable UWB MIMO applications.

A compact 4 × 4 reconfigurable MIMO antenna design with adjustable suppression of certain frequency bands within the UWB frequency range

This paper introduces a novel 4 × 4 multiple-input multiple-output (MIMO) antenna design with a reconfigurable operating band within the Ultra-Wideband (UWB) range. The antenna consists of four rectangular radiating elements arranged symmetrically and orthogonally on a defected ground plane. The design incorporates switching elements that allow adjustable and reversible suppression of specific bands within the UWB range, enabling the antenna to operate in three different modes: UWB, X-band, and dual-band with sub-6GHz and X-band. Thus, a single UWB antenna can serve as three different antennas, suppressing certain frequencies as required. To mitigate mutual coupling between adjacent antenna elements, four thin stubs are strategically placed at the center of the ground plane, forming a square with open corners. When one of the antenna elements is excited, this structure acts as an insulator, ensuring that the surface current is confined solely to that element and not induced in others. Experimental verification of the proposed design was performed by fabricating and testing the antenna. The results indicated good agreement between simulation and measurement data for various parameters, including S-parameters, radiation patterns, gains, and MIMO parameters such as envelope correlation coefficients (ECC), diversity gain (DG), mean effective gain (MEG), and total active reflection coefficient (TARC).

Dual-Band MIMO Antenna with Four CPW Elements using Polarization Diversity for 5G Mobile Communication Networks and Satellite

In this paper, a novel design of compact quad-element MIMO (Multiple Input Multiple Output) antenna for 5G communication networks and satellites is proposed. The four similar elements of this antenna are placed perpendicularly to each other on a 40x40 mm2 FR4 substrate. Each element is fed by a CPW (coplanar waveguide) line. Two slits and an I-shaped slot are etched into the patch, and by varying their parameters; a good matching is achieved in the lower (4.9 GHz) and upper (17 GHz) frequency bands. However, 25 and 30 dB isolations are attained in the lower and upper bands, using the polarization diversity technique and adding stubs on the ground plane. A prototype of the proposed antenna is fabricated and measured. Moreover, the performance of the MIMO antenna is studied in terms of ECC (envelope correlation coefficient), DG (diversity gain), TARC (total active reflection coefficient), realized gain, efficiency, and radiation pattern, validated with the measured results, and showed a good agreement.

Higher Order MIMO Antenna Design Using Capacitively Coupled Meandered Loop Element for 5G Smartphone Applications

In this paper, a compact 10-element multiple-input multiple-output (MIMO) antenna system for fifth generation (5G) wireless communication system is presented. The antenna structure has a T-shaped feeding element and a reduced size capacitively coupled meandered loop radiating element. The proposed MIMO antenna system is operating at 3.5 GHz. The MIMO antenna element is self-isolated and it has a compact size of 13.45×6 mm2. It exhibits very good isolation of more than 15 dB without using any external decoupling structure like a neutralization line or slot technique. Furthermore, performance parameters like total efficiency are around 40-64%, envelope correlation coefficient (ECC) is below 0.02, while gain of all antennas is between 3-3.4dBi. The performance of the proposed MIMO antenna is also verified through the measurement of its fabricated prototype. In this paper, a compact 10-element multiple-input multiple-output (MIMO) antenna system for fifth generation (5G) wireless communication system is presented.

4X4 MIMO slot antenna spanner shaped low mutual coupling for Wi-Fi 6 and 5G communications

Multiple-input multiple-output (MIMO) antennas are essential for modern wireless communication systems that require high data rates, reliability, and quality. However, designing MIMO antennas poses several challenges, such as achieving high isolation, low mutual coupling, low envelope correlation coefficient (ECC), high gain, and high efficiency in a compact size. In this paper, we propose a novel MIMO antenna design that can overcome these challenges and support various wireless applications, such as WiFi-6, 5G (n77/n78/n79), and satellite communications. The proposed design consists of four spanner-shaped radiating elements that are etched on an FR-4 substrate with a tapered feeding line. The spanner-shaped antenna is derived from an octagonal ellipse that is cut by another octagonal ellipse to form the shape of the antenna. The proposed design achieves dual operating bands of 3.3–3.8 GHz and 4.5–8.4 GHz with low mutual coupling (<−10 dB), low ECC (less than0.05), high gain (up to 4 dBi), and high efficiency (>80%). The proposed design is compared with other MIMO antenna designs in the literature and shows its advantages in terms of size, performance, and applicability.

Advances in MIMO Antenna Design for 5G: A Comprehensive Review.

Multiple-input multiple-output (MIMO) technology has emerged as a highly promising solution for wireless communication, offering an opportunity to overcome the limitations of traffic capacity in high-speed broadband wireless network access. By utilizing multiple antennas at both the transmitting and receiving ends, the MIMO system enhances the efficiency and performance of wireless communication systems. This manuscript specifies a comprehensive review of MIMO antenna design approaches for fifth generation (5G) and beyond. With an introductory glimpse of cellular generation and the frequency spectrum for 5G, profound key enabling technologies for 5G mobile communication are presented. A detailed analysis of MIMO performance parameters in terms of envelope correlation coefficient (ECC), total active reflection coefficient (TARC), mean effective gain (MEG), and isolation is presented along with the advantages of MIMO technology over conventional SISO systems. MIMO is characterized and the performance is compared based on wideband/ultra-wideband, multiband/reconfigurable, circular polarized wideband/circular polarized ultra-wideband/circular polarized multiband, and reconfigurable categories. The design approaches of MIMO antennas for various 5G bands are discussed. It is subsequently enriched with the detailed studies of wideband (WB)/ultra-wideband (UWB), multiband, and circular polarized MIMO antennas with different design techniques. A good MIMO antenna system should be well decoupled among different ports to enhance its performance, and hence isolation among different ports is a crucial factor in designing high-performance MIMO antennas. A summary of design approaches with improved isolation is presented. The manuscript summarizes the various MIMO antenna design aspects for NR FR-1 (new radio frequency range) and NR FR-2, which will benefit researchers in the field of 5G and forthcoming cellular generations.

Design of a high isolation tri-band MIMO antenna for coal mine applications

ABSTRACT In this paper, a tri-band multiple-input multiple-output (MIMO) antenna with high isolation characteristic is designed and fabricated for coal mine applications. It is composed of two symmetrical trident planar monopoles which can achieve tri-band characteristics. The isolation between the elements is higher than 20 dB across the whole frequency region by firstly placing the two elements symmetrically, loading a T-shaped branch and etching two rectangular slots on the ground successively. The proposed antenna can operate at three bands, i.e., 1.85∼2.70 GHz, 3.24∼3.99 GHz and 4.65∼5.80 GHz, which simultaneously cover the operating frequency band of WiMAX, WiFi, 4G, and 5G New Radio (NR) for mining. Good agreements can be observed between the simulated and measured results. The designed tri-band MIMO antenna has the advantages of low profile, compact structure and easy to conform with the platform, thus having a broad prospect in coal mine applications.

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.