Metamaterial‐based highly isolated MIMO antenna system for 5G smartphone application

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

A dual-mode, dual-port pattern diversity antenna is presented for 2.45-GHz wireless body area networks. This antenna provides multiple radiation patterns as desired for both on- and off-body applications, namely an omniazimuthal radiation pattern directed along the body and a broadside radiation directed away from the body, respectively. This was achieved by exciting the fundamental TM11 mode in a classical circular patch antenna for off-body radiation and the TM01 mode in another circular patch antenna for on-body radiation, which was enforced by using a short circuit between the patch and the ground plane. The two antenna prototypes were finally stacked together into a single package, and the feed positioning had been optimized to offer negligible coupling between the two antenna ports that excite the two modes. The antenna performance has been evaluated in proximity to the body and found to be quite stable, compared to the performance in the free space. Moreover, the diversity performance of the antenna has also been evaluated in the form of an envelope correlation coefficient (ECC) and a diversity gain (DG). The ECC has been observed to be close to zero with a corresponding DG close to 10 dB at 2.45 GHz. This also suggests the suitability of the proposed antenna for diversity and multiple-input–multiple-output systems.

Reconfigurable orthogonal quad-port MIMO antenna for DSRC, WLAN, RADAR and Ku-band applications

The work proposes a low-profile, wideband circularly polarized (CP) dual-element Multiple-Input-Multiple-Output (MIMO) antenna design for C-band and selected 3GPP FR1 5G NR bands. The designed two-element MIMO antenna utilizes a planar patch configuration and achieves high isolation by strategically incorporating an optimized rectangular-shaped slot in the ground plane of the antenna, which acts as a decoupling structure, eliminating the need for any external complex structure. The two MIMO elements are placed with an optimized decoupling slot of 7 mm width to reduce mutual coupling between them. The performance of the proposed CP-MIMO antenna has been validated comprehensively through both full-wave simulations and experimental measurements. The antenna demonstrates a measured −10 dB impedance bandwidth of 3.81 GHz (4.24–8.05 GHz) and a 3-dB axial ratio bandwidth (ARBW) of 2.7 GHz (4.36–7.06 GHz), validating CP performance. The key MIMO parameters investigated include Total Active Reflection Coefficient (TARC < −10 dB), Envelope Correlation Coefficient (ECC < 0.005), Diversity Gain (DG ≈ 9.98), and Channel Capacity Loss (CCL ≈ 0.35 bits s −1 Hz −1 ), confirming its excellent diversity standards. The proposed CP MIMO antenna occupies a compact footprint of 49 × 24 × 1.6 mm 3 , with better inter-element isolation of more than 20 dB across most of the operating band, a peak gain of 5.7 dB, high simulated efficiency of 96%, and polarization agility. Furthermore, the scalability of the design has been comprehensively demonstrated by extending it to 3-port and 4-port MIMO configurations, supported by detailed simulation results. These results validate its suitability for integration into next-generation wireless communication systems.

In this article, compact a multiple-input and multiple-output (MIMO) system with flag-shaped radiators and a mountain-shaped ground plane is presented. Isolation is enhanced with the help of a decoupling stub placed between radiators, where two bands are stopped with the help of slits etched into the radiators. The overall size of the proposed antenna is 15 mm ×25 mm ×1.6 mm. The reflection coefficients are less than -10 dB between 3–10.9 GHz, except the bands WiMAX (3.2–3.7 GHz) and WLAN (5–6 GHz); similarly, measured and simulated transmission coefficients are less than -20 dB across the entire band of UWB. The envelope correlation coefficient (ECC) is less than 0.02 and the diversity gain is greater than 9.9 dB. The gain, ECC, radiation pattern, multiplexing efficiency, diversity gain and various other parameters are discussed and evaluated in detail.

A flexible transparent wideband four-element MIMO antenna with a connected ground plane is proposed with numerical computation and experimental measurement studies. The optical transparency is obtained using flexible conductive oxide material AgHT-4 and Melinex substrate. The radiating elements are in the form of circular stub-loaded C-shaped resonators, which are positioned in a carefully structured flexible Melinex substrate with an interconnected partial ground plane structured in the form of an L-shaped resonator, attaining an overall antenna size of 0.33λ × 0.48λ at the lowest operating frequency. The proposed antenna spans over a.10 dB impedance bandwidth of 2.21-6 GHz (92.32%) with an isolation level greater than 15dB among all elements. The maximum gain is 0.53dBi with a minimum efficiency of 41%, respectively which is satisfactory considering flexible structure and sheet impedance of 4Ω/sq. MIMO antenna parameters in terms of the envelope correlation coefficient (ECC) and diversity gain (DG) are also extracted where all the values are satisfactory for MIMO applications. The bending analysis of the proposed transparent MIMO antenna along the X and Y axis has revealed good performance in terms of scattering parameters and radiation pattern along with MIMO diversity performance. All of these technical points make the flexible MIMO antenna suitable for smart devices using sub-6 GHz 5G and WLAN band in IoT applications where visual clutter and co-site location issues need to be mitigated with the integration ease of conformal placement on the curved component/device surfaces.

This article presents a symmetrical reduced-size eight-element MIMO antenna array with high electromagnetic isolation among radiators. The array utilizes easy-to-build techniques to cover the n77 and n78 new radio (NR) bands. It is based on an octagonal double-negative metamaterial split-ring resonator (SRR), which enables a size reduction of over 50% for the radiators compared to a conventional disc monopole antenna by increasing the slow-wave factor. Additionally, due to the extreme proximity between the radiating elements in the array, the modal significance (MS) method was employed to identify which propagation modes had the most impact on the electromagnetic coupling among elements. This approach aimed to mitigate their effect by using an electromagnetic barrier, thereby enhancing electromagnetic isolation. The electromagnetic barriers, implemented with strip lines, achieved isolation values exceeding 20 dB for adjacent elements (<0.023 λ) and approaching 40 dB for opposite ones (<0.23 λ) after analyzing the surface current distribution by the MS method. The elements are arranged in axial symmetry, forming an octagon with each antenna port located on a side. The array occupies an area of 0.32 λ2 at 3.5 GHz, significantly smaller than previously published works. It exhibits excellent performance for MIMO applications, demonstrating an envelope correlation coefficient (ECC) below 0.0001, a total active reflection coefficient (TARC) lower than -10 dB for various incoming signals with random phases, and a diversity gain (DG) close to 20 dB.

A four-element compact wide-band optically transparent MIMO antenna with a full ground plane is proposed. The four elements transparent MIMO system has a compact size of 24x20 mm(2) with the undivided ground plane as most of the real-time systems demand a common reference. The complete antenna system achieves around 85% transparency due to a combination of AgHT-8 and Plexiglas which forms the transparent conductive patch/ground and substrate, respectively. The antenna geometry leads dual-band operation ranging from 24.10 - 27.18 GHz (Impedance bandwidth D 12%) and 33 - 44.13 GHz (Impedance bandwidth D 28.86%) targeting the mm-wave 5G applications. The 4-element antenna system achieves isolation between inter-elements &amp;gt; 16 dB and maximum gain value of greater than 3 dBi with more than 75% efficiency. The proposed transparent MIMO antenna is evaluated in terms of diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and mean effective gain (MEG) where decent MIMO performance with isolation more than &amp;gt;16 dB between the adjacent and other elements is achieved. Transparent MIMO antenna achieves directional patterns for the operating band with the value of DG &amp;gt; 9, ECC &amp;lt; 0.1, TARC value less than and the ratio of MEG within the agreed limit of +/- 3 dB conforming acceptable MIMO/diversity performance.

This article presents a compact ultra-wideband (UWB) circular monopole antenna with a frequency-selective surface (FSS) for gain enhancement. The proposed antenna has a circular patch with circular cuts at the edges and is excited by a microstrip feed. The bottom plane is truncated and further modified by two triangular cuts at the sides and one rectangular cut in the middle to improve the radiation characteristics of the UWB antenna. The antenna is designed on an FR-4 substrate with a thickness of 1.6 mm, a relative permittivity of 4.3, and planner dimensions of 30 mm × 30 mm. To improve the proposed antenna’s gain, an FSS is designed that consists of periodic unit cells of metal printed on the upper layer of an FR-4 substrate with dimensions of 0.11λ × 0.11λ at the lowest operating frequency of 3.3 GHz. The FSS shows a very low transmission coefficient and linearly reducing reflection phase with increasing frequency over a frequency range of 3.3–10.8 GHz. The gain of the proposed antenna is increased from 3 dB to 8.1 dB at 9 GHz by placing the antenna on the FSS. Moreover, the prototype of the proposed antenna is fabricated, and the experimental results are measured, which show close agreements with simulated results. The FSS-based antenna has directional radiation patterns, making it a potential candidate for ground-penetrating radar and UWB applications.

In the paper, an extremely compact multiple-input-multiple-output (MIMO) antenna is proposed for portable wireless ultrawideband (UWB) applications. The proposed prototype consists of four monopole antenna elements, which are placed perpendicularly to achieve polarization diversity. In addition, the mutual coupling between antenna elements is suppressed by designing the gap between the radiation element and the ground plane. Moreover, a matching stub has been connected to the feedline to ensure impedance matching in high frequency. Both simulated and measured results indicate that the proposed antenna has a bandwidth of 3–20 GHz, with a high isolation better than 17 dB. In addition, the designed MIMO antenna offers excellent radiation characteristics and stable gain over the whole working band. The envelope correlation coefficient (ECC) is less than 0.1, which shows that the antenna can meet the polarization diversity characteristics well.

Tuning the higher to lower order resonance frequency ratio and implementing the tunable THz MIMO/self-diplexing antenna

In this paper, a two-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is designed, fabricated, and tested based on characteristic mode theory. The MIMO design consists of two circular patches which are connected to the UWB unit with an I-shaped branch. Slots are opened in the circular patch to enhance the impedance matching performance, and in order to improve the isolation of the antenna while operating, metal strips are added to the patch, and a fence decoupling structure. The overall size of the proposed antenna is 77.5 × 39 × 1 mm3, and the microstrip feed is used. Simulation results show that the antenna can cover the 2.68-11.85 GHz band with a return loss of -43.5 dB, an isolation of less than -20 dB, and an envelope correlation coefficient (ECC) of < 0.007. It possesses good directional radiation characteristics, and it can be used in 5G MIMO communication systems.

A dual-port MIMO antenna system for 5G and Wi-Fi 6E communications using a parasitic element

The present work represents polarization reconfigurable MIMO antenna which is design to work at 2.4 GHz (WLAN) and C band application. An inverted U-shaped slot and two PIN diodes per radiator are incorporated in the circular patch antenna to achieve polarization reconfigurability between Linear and Circular polarization (RHCP or LHCP). A simple rectangular strip is utilized between the radiators to achieve isolation improvement from -14 dB to -22dB in the proposed design. Computer Simulation Technology (CST) 2018 is used to design and validate the polarization reconfigurable MIMO antenna with sufficient isolation. Surface current distribution, Envelope Correlation Coefficient (ECC) and Diversity Gain (DG) and axial ratio are calculated using simulation software and used to validate circularly polarized MIMO design’s diverse behavior. The design is fabricated in low-cost FR-4 material and measurement is done to verify the simulation results. The measurement results show close agreement with simulated results and proves that the proposed design can be a better candidate for WLAN and C band application with polarization reconfiguration properties.

This paper describes the integration of multiple microstrip patch antenna elements into a small handset. The antenna system has been developed for multiple-input multiple- output (MIMO) applications in WLAN systems at 5 GHz. Four square microstip patches are printed on the top area of a 45mmxl05 mm ground plane, representing the back side of a typical small handset. The small ground plane integration effects on input return loss, mutual coupling, envelope correlation and radiation pattern, are evaluated. An antenna prototype has been fabricated and tested. Good agreement has been obtained between numerical simulations and experimental results.