Wideband Multiple-input Multiple-output Antenna Research Articles

Metasurface absorber for millimeter waves: a deep learning-optimized approach for enhancing the isolation of wideband dual-port MIMO antennas

In this communication, the concept of metasurface absorber is utilized to enhance the isolation in the dual port multiple-input multiple-output (MIMO) antenna specially designed for a wideband millimeter wave operation. The frequency of operation of the designed module is 32.5–42.5 GHz with sufficient gain attributes. The designed metasurface array consists of two circular rings on two different layers. The concept of deep learning is utilized to optimize the dimensional configuration of the metasurface to achieve the maximum absorption of electromagnetic waves in the band of interest. The suppression of mutual coupling by double-ring metasurface is analyzed with the help of the wave theory concept. In contrast to previous decoupling methods using metasurfaces, the suggested metasurface is intended to be in the same plane as the array. The findings demonstrate the capability of effectively separating antenna elements in wideband MIMO antenna without compromising the geometrical complexity. Diversity metrics such as envelope correlation coefficient (ECC), mean effective gain (MEG), channel capacity loss (CCL), and total active reflection coefficient (TARC) for the proposed frequency range are also used to evaluate the performance of the constructed MIMO antenna. The wideband characteristics with a compact configuration make the design MIMO module a suitable candidate for mm-wave applications. The congruence between simulation and measurement confirms the validity of the suggested design.

A compact wideband MIMO antenna with efficient isolation for S and C-bands applications

This work explored a wideband Multiple Input Multiple Output (MIMO) antenna that has a compact rectangular shape, a rectangular stair slot, and a C-shaped metamaterial for isolation improvement. A wideband antenna has been developed and fabricated to determine the effectiveness of a specified metamaterial. To get minimum mutual coupling, the C-shaped metamaterial is positioned between the two rectangular antennas. According to the simulation, the MIMO antenna operates between 2.61 GHz and 7.64 GHz (5.03 GHz). Peak gain of the designed MIMO antenna from 3.4 to 9.1 dB. The envelope correlation coefficient (ECC) is < 0.03, diversity gain (DG) is > 9.99, mean effective gain (MEG) is < − 3 dB, and channel capacity loss (CCL) 0.005 is accomplished. The measured and simulated outcomes are in close acceptance of the performance parameter. Thus, the designed MIMO antenna is ascendancy for S and C-band applications such as Wi-Fi, Satellite up and downlink, and 5G.

A compact quad element human face‐shaped wideband MIMO antenna for 5G applications

SummaryThis article presents a quad element wideband multiple‐input multiple‐output (MIMO) antenna consisting of human face‐shaped patch radiators with defected ground structure (DGS) having rectangular split ring resonator (RSRR) in ground surface. The measured bandwidth of the proposed MIMO antenna is 3.0–6.5 GHz, and the isolation between the ports is more than 16 dB. Additionally, simulated diversity characteristics like the channel capacity loss (CCL), channel capacity (CC), total active reflection coefficient (TARC), mean effective gain (MEG), and envelope correlation coefficient (ECC) are investigated with the measured value and observed to be within the acceptable ranges over the operating frequency band. The suggested antenna can be used in the wireless local area network (WLAN) (i.e., 4.9–5.725 GHz), wireless fidelity (Wi‐Fi) (i.e., 5.15–5.85 GHz), and 5G under 6 GHz (3.3–5.0 GHz) frequency ranges.

Circumferential slots based decoupled wideband MIMO antenna for 5G and sub-6 GHz applications

This paper investigates a small size 2 × 2 wideband multiple input multiple output (MIMO) antenna covering frequency band of 2.61 to 5.52 GHz. The antenna structure consists of elliptical ring patch with multiple circumferential slots. The edge-to-edge separation between the patches are kept 3.6 mm with volumetric dimensions of 30 × 46 × 1.6 mm3. The narrow slits are etched in the tapered ground plane to obtain the wideband characteristics. The electromagnetic coupling is improved more than 16 dB by employing the neutralization technique. The measured average gain and radiation efficiency of the proposed antenna are above 2.61dBi and 83.54%, respectively across the operating band. In addition to that, the important MIMO diversity parameters are investigated. The group delay and signal analysis in different orientations are also studied to ensure the quality performance of the antenna. The proposed MIMO antenna is simulated using CST microwave studio and further validated with the measurements. In addition to that, the parallel and orthogonal configuration of 4 × 4 MIMO antennas are analyzed by extending the proposed 2 × 2 MIMO design. The 4-port MIMO antennas exhibit the operating frequency bands varying from 2.80 to 5.58 GHz and 3.4 to 5.52 GHz, respectively for parallel and orthogonal MIMO configurations. The diversity parameters of 4-port MIMO antennas are calculated and compared with the measured results to verify its practical applications. Finaly, the SAR analysis of the antenna is presented at 3.08 and 5.20 GHz for 1/10 g tissues and are found 0.111/0.106 and 0.079/0.063 W K−1g−1, respectively. The proposed MIMO antenna designs are suitable for modern high-speed communication for 5G and sub-6 GHz frequency bands.

Non-conventional leather substrate based high isolation wideband MIMO antenna for body-centric applications

This work presents the design of a dual-port high isolation compact wideband wearable multiple-input multiple-output (MIMO) antenna employing a non-conventional leather substrate material. The designed antenna structure comprises defected structure at the ground plane, including two semicircular slots and two 'H' shaped stubs in the cascaded form to minimize the coupling effect between the antenna ports. The antenna works over the 2.22–8 GHz frequency range with a fractional bandwidth of 113.12 %, covering the application bands of WLAN (2.4–2.484 GHz), WiMAX (3.2–3.85 GHz), WLAN (5.15–5.35 GHz/5.725–5.825 GHz), C band downlink/uplink (3.7–4.2 GHz/5.925–6.425 GHz) and downlink defense (7.2–7.7 GHz) band. The suggested antenna provides port isolation above 27 dB, envelope correlation coefficient (ECC) under 0.09, diversity gain (DG) above 9.94 dB, channel capacity loss below 0.33 Bits/Sec/Hz, low magnitude ratio between mean effective gains of two ports (<0.1 dB), and a stable total active reflection (TARC) over the active spectral region. The designed antenna offers a SAR value less than the threshold level (<1.6 W/kg). The constructed MIMO antenna structure consumes a volume of 32 × 52 × 2 mm3.

A novel wideband fractal‐shaped MIMO antenna for brain and skin implantable biomedical applications

SummaryA novel fractal‐shaped wideband multiple‐input multiple‐output (MIMO) antenna is proposed for brain and skin implantable applications. This antenna works in the 2.4–2.48 GHz band of industrial, scientific, and medical (ISM) standards. The fractal‐shaped wideband MIMO antenna is miniature in size with a footprint of . Rogers RT/Duroid 6010 high‐dielectric substrate material is used to fabricate the optimized design in order to validate the implantable MIMO antenna structure. The same high‐permittivity substrate material has been used as a superstrate. Experiments were carried out in brain and skin‐mimicking gel at 2.45 GHz in the ISM band. The proposed antenna has a peak gain of −21.3 dBi at 2.45 GHz. High isolation (&gt;20 dB) between two MIMO ports is attained. The proposed antenna achieves a fractional bandwidth of 36.76% and an impedance bandwidth of 1.02 GHz. According to IEEE safety regulations for 1‐ and 10‐g tissues, the computed maximum specific absorption rate (SAR) is safe bound.

A High-Gain and Wideband MIMO Antenna for 5G mm-Wave-Based IoT Communication Networks

In this paper, an antenna with a multiple-input, multiple-output (MIMO) configuration is demonstrated for mm-wave 5G-based Internet of Things (IoT) applications. The two antenna elements are arranged next to each other to form a two-port antenna system such that significant field decorrelation is achieved. Moreover, a dielectric layer is backed by an eventual multiport system to amend and analyze the radiation characteristics. The overall size of the MIMO configuration is 14 mm × 20 mm, and the operation bandwidth achieves ranges from 16.7 to 25.4 GHz, considering the −10 dB criterion with a maximum isolation of more than −30 dB within the operating band. The peak gain offered by the antenna system is nearly 5.48 dB, and incorporating a dielectric layer provides an increase in the gain value to 8.47 dB. Within the operating band, more than 80% total efficiency is observed, and analysis shows several MIMO performance metrics with favorable characteristics. The compactness of the proposed design with high isolation, improved gain, and wideband features make it a suitable candidate for mm-wave-based 5G applications.

Wideband self-decoupled MIMO antenna element based on coupled-loop antenna for 5G smartphones

A novel wideband self-decoupled loop-coupled antenna element is proposed for the fifth-generation (5G) multiple-input multiple-output (MIMO) smartphones. The proposed loop-coupled antenna element generates two resonance modes of 0.75 and 1 λ. With the help of these two resonance modes, a wide bandwidth is achieved. The self-decoupled performance is realized by loading the loop antenna element with coupled lines. The common/differential mode theory is used to analyze and guide the antenna design to clarify the self-decoupling principle. At the same time, miniaturization of the proposed antenna element is also studied. The antenna element provides good isolation and diversity/multiplexing performances over N77/N78/N79 bands. An 8-port MIMO antenna is constructed using the proposed antenna element. The MIMO antenna is simulated, manufactured, and tested to verify and evaluate the performance metrics, such as isolation, envelope correlation coefficient, efficiency, and spatial multiplexing efficiency. The test results are in good agreement with the simulated ones.

High-Isolation wideband MIMO antenna with offset T-Shaped slots for 5G/WLAN applications

A broadband multiple-input multiple-output (MIMO) antenna with high isolation operating in 3.14–5.42 GHz (2.28 GHz, 53.3%) is proposed for 5G smartphones. An offset T-shaped slot with dual functions is employed to improve the bandwidth of one antenna element and enhance the isolation. Then, the double L-shaped stubs are loaded to improve the impedance matching of the other antenna in the MIMO antenna. Finally, the 2 × 2 MIMO antenna is constructed by four T-shaped monopole antennas, two double L-shaped stubs, and two offset T-shaped slots. The proposed MIMO antenna is first simulated and then experimentally tested with a good agreement. High isolation of greater than 15 dB, high antenna efficiency of more than 54%, and low envelope correlation coefficient (ECC) of smaller than 0.08 are realized within 3.14–5.42 GHz. These good performances indicate that the proposed antenna can be applied for MIMO applications in smartphones.

DGS based miniaturized wideband MIMO antenna with efficient isolation for C band applications

Abstract A wideband multiple-input multiple-output (MIMO) antenna for C-band applications is presented in this paper. It consists of 2 × ${\times}$ 1 hexagonal motifs which serves as radiating elements. The side of each hexagonal element is 5.73 mm and the overall dimension of the proposed MIMO antenna is 30 × ${\times}$ 20 × ${\times}$ 1.6 mm3. The hexagonal motifs are embedded on inexpensive FR-4 lossy substrate. Thereafter, a circle with radius 1 mm is etched at the center of each hexagonal motif. Inverted L-shaped stubs are employed to attain efficient isolation between the nearby antenna elements. Four inverted L-shaped stubs are included to further enhance the isolation and eliminate the antenna size increment simultaneously, by suppressing the surface waves. Before using the decoupling approach, the MIMO antenna had an impedance bandwidth of 6.7 GHz and an isolation of −20 dB. The suggested antenna’s impedance bandwidth and isolation are 5.83 GHz and −52 dB, respectively, after using a decoupling approach (inverted L-shaped stub). The proposed MIMO antenna had a peak gain and radiation efficiency of 3–7 dBi and better than 90% (with decoupling), 2.75 to 6 dBi and greater than 60% (without decoupling). To verify the proposed design, a prototype was developed to compare the simulated parameters with the measured one. The envelope correlation coefficient (ECC) was less than 0.05, and channel capacity loss (CCL) less than 0.3 was achieved with DGS. Besides, scattering matrix such as return loss S 11 and transmission coefficient S 21 between two elements, radiation pattern, and current distribution was also favorable. Thus, the proposed MIMO antenna is advantageous to be used for C-band applications such as developing new generation air-borne and space-borne radars, as well as X-band applications.

Gain and isolation enhancement of a wideband MIMO antenna using metasurface for 5G sub-6 GHz communication systems

This work proposes a compact metasurface (MS)-integrated wideband multiple-input multiple-output (MIMO) antenna for fifth generation (5G) sub-6 GHz wireless communication systems. The perceptible novelty of the proposed MIMO system is its wide operating bandwidth, high gain, lower interelement gap, and excellent isolation within the MIMO components. The radiating patch of the antenna is truncated diagonally with a partially ground plane, and a metasurface has been employed for enhancing the antenna performance. The suggested MS integrated single antenna prototype has a miniature dimension of 0.58λ × 0.58λ × 0.02λ. The simulated and measured findings demonstrate a wideband characteristic starting from 3.11 to 7.67 GHz including a high realized gain of 8 dBi. The four-element MIMO system has been designed by rendering each single antenna orthogonally to one another while retaining compact size and wideband properties between 3.2 and 7.6 GHz. The suggested MIMO prototype has been designed and fabricated on a low loss Rogers RT5880 substrate with a miniature dimension of 1.05λ × 1.05λ × 0.02λ and its performance is evaluated using a suggested 10 × 10 array of a square enclosed circular split ring resonators within the same substrate material. The inclusion of the proposed metasurface with a backplane significantly reduces antenna backward radiation and manipulates the electromagnetic field, thus improving the bandwidth, gain and isolation of MIMO components. The suggested 4-port MIMO antenna offers a high realized gain of 8.3 dBi compared to existing MIMO antennas with an excellent average total efficiency of 82% in the 5G sub-6 GHz spectrum and is in good accordance with measured results. Furthermore, the developed MIMO antenna exhibits outstanding diversity characteristics in respect of envelope correlation coefficient (ECC) less than 0.004, diversity gain (DG) close to 10 dB (> 9.98 dB) and high isolation between MIMO components (> 15.5 dB). Therefore, the proposed MS-inspired MIMO antenna substantiates its applicability for 5G sub-6 GHz communication networks.

A wideband self‐decoupled multi‐input multi‐output antenna with a high isolation

A wideband MIMO antenna, which consists of two adjacent antenna elements with a very close distance (2 mm or 0.026λ), is suggested to achieve a good isolation by the principle of common mode (CM, in-phase signals) and differential mode (DM, out-of-phase signals) cancelation without using any additional decoupling structure in this article. Compared with its reference design, the measured results demonstrate that the isolation of proposed design can be improved to better than 20 dB in a wider bandwidth of 3.2–5.9 GHz (59%), with S11 and S22 < −10 dB. The experimental efficiency and envelope correlation coefficients are larger than 78% and <0.04 for the proposed design, respectively. The proposed multiple-input multiple-output (MIMO) antenna array, with good isolation and diversity performance, exhibits broad application prospects in the tightly arranged MIMO antennas of 5G mobile devices.

Wideband MIMO Antenna Isolation Enhancement Using 4th-Order Cross-Coupled Decoupling Circuit

This article presents a new fourth-order stub-based decoupling circuit for isolation improvement in a wideband tightly coupled multiple-input–multiple-output (MIMO) antenna array. The proposed decoupling circuit uses a fourth-order coupling-resonator filter effect and is designed using the structure’s admittance parameter. In the decoupling circuit, the pair of dual-band second-order stub-based filters is used for the desired band’s lower and upper frequencies. Finite transmission zeros provide cross-coupling, which helps maintain the admittance slope stopband between these bands and reduces coupling among MIMO elements. The proposed fourth-order decoupling circuit concept can be utilized for different wideband MIMO antenna applications to redesign the targeted band and cross-coupling scenario properly. In addition, to demonstrate the proposed decoupling circuit concept’s influence in achieving good wideband isolation in a compact dimension of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$45\times 40\times1.6$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , octagonal- and circular-shaped patch MIMO antennas are analyzed. To analyze the impact of the proposed decoupling circuit of the dimension <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11.3\times11$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the design, edge-to-edge separation between MIMO elements is kept at a minimum of 0.2 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.0035\lambda _{0 \thinspace }$ </tex-math></inline-formula> at 5.4 GHz, WLAN band). This demonstrates that the decoupling circuits are antenna-independent and can be applied to other MIMO antennas. The measured S-parameters of the proposed wideband MIMO antenna present high isolation (>20 dB) between the antenna elements. Moreover, the proposed solutions’ radiation behavior and diversity performance are evaluated. The MIMO antenna element measured radiation efficiency is increased from 50% to 75%. It demonstrates good properties that make it a suitable contender for advanced scientific applications.

Extra Wide Band MIMO Antenna with High Isolation and Low Correlation at 38 GHz mm-Wave Frequency Band for 5G Applications

A compact wide-band Multiple Input Multiple Output (MIMO) antenna having highest isolation and least correlation for millimeter-wave 5G communications is proposed in this paper. Firstly, a single antenna was designed and simulated to be working at 38 GHz, a potential target band for 5G applications. It consists of a 5-shaped radiating patch, with partial ground plane. Its length is adjusted and a wide bandwidth is obtained. Then, the two antenna elements are closely positioned with edge-to-edge spacing of 1 mm (0.55 λ, with λ is the free space wavelength at resonance). Thanks to the technique of spatial diversity, a high degree of isolation is attained; more than 25 dB in the whole bandwidth. Moreover, correlation value is under 0.0002 in the working band. The prototype antennas are fabricated and measured. The result indicates that this antenna shows a reflection coefficient under -10 dB over a range of frequencies from 32.3 to 54.6 GHz (BW=22.3 GHz, 58.68% fractional bandwidth). The antenna presents a high realized gain of 7.12 dBi and radiation efficiency of about 82.46% at the desired frequency. Due to these results, our antenna may be regarded a suitable candidate for mm-wave 5G MIMO applications.

Sub-6 GHz Highly Isolated Wideband MIMO Antenna Arrays

This study proposes a compact four-port multiple-input multiple-output (MIMO) antenna system to operate within a frequency range of 3.2–5.75 GHz to serve in 5G new radio (NR) sub-6 GHz n77/n78/n79 and 5 GHz WLAN with good impedance matching. To increase the isolation between the MIMO antenna elements with low complexity and cost, the antenna elements are orthogonally oriented to each other with distance spacing of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.3\lambda _{\text {o}}$ </tex-math></inline-formula> between elements, including electromagnetic bandgap (EBG) structure, defected ground structure (DGS), capacitive elements (CE), and neutralization line (NL). The simulation results show that the measured mutual coupling between the array elements is improved from −20 to −45 dB. The envelope correlation coefficient is enhanced. In addition, the diversity gain, mean effective gain, and total active reflection coefficient are improved simultaneously. The suggested structure has been designed on CST Microwave Studio 2019. The antennas’ overall dimensions for all methods are the same as they approach 46 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times46$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.6$ </tex-math></inline-formula> mm. The measured gain of the proposed designs ranges from 6 to 9 dBi, and the radiation efficiency approaches 90%. The antennas are fabricated and tested, where better experimental results are noticed compared to the simulation results. Our antennas are designed over FR-4 substrate with a noticeable cost reduction. Each antenna element has a dimension of 15 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times23$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.6$ </tex-math></inline-formula> mm. An “EL” slot into the radiating element and two identical stubs coupled to the partial ground are used to improve the impedance matching and radiation characteristics across the bands of interest. The isolation decreases by 22 dB using the EBG method, reaching the value of −65 dB. Meanwhile, the isolation decreases by 19 dB using the DGS method, reaching −60 dB. Due to gaps between adjacent unit cells and the capacitance generated from the dielectric gap between the top metallic patch and ground plane, the EBG method gives the best results. However, in the CE method, capacitances resulting from the four transmission lines in the bottom side of the antennas (parasitic elements) decrease the isolation by 15 dB, reaching −40 dB. NL method makes the isolation to reach the value of −55 dB. Accordingly, the proposed antenna arrays support 5G NR sub-6 GHz n77/n78/n79 and 5 GHz WLAN, where n77 (3.3–4.2 GHz), n78 (3.3–3.80 GHz), and n79 (4.4–5.0 GHz) require a wideband coverage that extends from 3.3 GHz to at least 5.0 GHz.

MICROSTRIP LINE-FED BASED QUAD-PORT WIDEBAND MIMO ANTENNA FOR K BAND APPLICATION

In this communication, a compact (30×30×1.6 mm3) microstrip line fed loaded quad-port and T-shaped wideband MIMO (Multiple-Input Multiple-Output) antenna for K band (18-27GHz) application is introduced. Here three simulated antennas (Antenna-1, Antenna-2 and Antenna-3) are analytically inspected in expressions of simulated gain, return loss (|S11|, |S22|, |S33| and |S44|), total active reflection coefficient (TARC), isolation (mutual coupling), diversity gain (DG), radiation efficiency, radiation pattern and envelope correlation coefficient (ECC). Antenna 3 disclaimers have been elevated for chosen antenna considerations and performance. The proposed antenna has |S11|, |S22|, |S33| and |S44| not more than -10 dB and the percentage impedance bandwidth is 19.54% (19.48-23.70GHz), 18.74% (19.58-23.63), 16.31% (19.54-23.01GHz) and 18.27% (19.39-23.29GHz) at ports 1, 2, 3 and 4 respectively. Simulated isolation is &lt; -15 dB, ECC obtained between ports 1-2, 1-3 and 1-4 is not more than 0.06, DG originated among the ports 1-2, 1-3 and 1-4 is in the range of 9.969-9.999 (dB), TARC &lt; 0 dB and radiation efficiency of 60% is obtained. The proposed design model of antenna has been analyzed with HFSS simulation tool by ANSOFT version 13.

High gain, wideband and low mutual coupling AMC-based millimeter wave MIMO antenna for 5G NR networks

A high gain and wideband multiple-input multiple-output (MIMO) for 5G new radio (NR) networks is introduced in this paper. The single unit is a monopole antenna with partial ground plane and two small triangles are cut out from the patch to produce the proposed frequency band. The two elements are located orthogonal to each other in order to reduce the mutual coupling without using isolation structure at the desired frequency 28 GHz. An artificial magnetic conductor (AMC) is located underneath the MIMO antenna to improve the gain by about 55% over the entire achieved frequency band (26-31.5 GHz). The Suggested antenna model with the AMC structure is fabricated to verify the simulation results in terms of S-parameters, radiation patterns, gain, and diversity parameters. It is worth noting that the experimental results have the same trend of the simulation ones which makes the suggested AMC-based MIMO antenna applicable for 5G NR networks.

Conformal screen printed graphene 4 × 4 wideband MIMO antenna on flexible substrate for 5G communication and IoT applications

Screen-printed graphene is integrated with multiple-input multiple-output (MIMO) technology to conquer the most concerned surge in electronic waste caused by the mass deployment of Internet of things (IoT) applications. A flexible MIMO antenna is implemented with simple fabrication process suitable for large-scale production by screen printing graphene highly conductive ink on paper substrate, ensuring high-speed 5G mass data wireless transmission without damaging the ecological environment. This environmental-friendly, low-cost, flexible and conformal MIMO antenna with orthogonal polarization diversity employs co-planar waveguide feed and planar pattern for achieving high space utilization and better integration in most scenarios, for instance, body centric networks and monitoring systems. Excellent performance has been achieved due to the high conductivity of the graphene: the fabricated antenna exhibits an average sheet resistance of . The bandwidth of the antenna ranges from (53.71% fractional bandwidth), covering long term evolution, sub-6 GHz mobile communication networks, 2.5 and 3.5 GHz WiMAX, and 2.4 and 3.6 GHz WLAN. Within this range, the antenna exhibits effective radiation, also its envelope correlation coefficient remains below , manifesting outstanding signal transmission quality in a variety of wireless networks. This work illustrates a novel aggregation of MIMO technology and graphene printing electronics, enabling cheap accessible and green MIMO antennas to be massively integrated in IoT applications.

Closely‐coupled wideband MIMO antenna with isolation improvement using decoupling circuit and hexagonal split‐ring resonators

AbstractIn this paper, a design of a closely‐coupled wideband multiple‐input–multiple‐output (MIMO) antenna using a new simple wideband decoupling circuit (DCkt) based on a 2nd order filter for isolation improvement is presented to decouple the wideband MIMO antenna array. The wideband closely‐coupled MIMO antenna and the DCkt are designed using the structure's admittance parameter. To achieve good isolation in wide‐bandwidth six hexagonal split‐ring resonators are utilized. The presented closely‐coupled wideband MIMO antenna is resonating at 5.08–6.30 GHz (WLAN) bands, with measured isolation (&gt;25 dB) in the 5.12–5.98 GHz frequency range. The envelope correlation coefficient is less than 0.1, and channel capacity loss (Closs) is less than 0.05, along with good radiation characteristics. It exhibits an exceptional expansion that makes the proposed solution the right candidate for advanced technological applications such as 5G and IoT.

A Dual Mode, Thin and Wideband MIMO Antenna System for Seamless Integration on UAV

Unmanned Aerial Vehicles (UAV’s), also known as autonomous drones, are being utilized for a variety of applications such as disaster management, search and rescue, surveillance, and remote monitoring. The wireless link to transfer the data from the drone to the ground station or another drone is critical for such applications. Antenna, being the most important part of that wireless link, must be designed such that it seamlessly integrates with the drone without affecting its flight. This means the antenna must be thin, lightweight, conformal, and provide wide coverage. On the other hand, antenna’s performance must not be deteriorated due to UAV mounting, so antennas with ground planes are preferred. Further, to cater for high data rate applications, a large bandwidth is required, which is difficult to achieve on thin substrates. In this paper, a dual band design is presented that addresses all the key requirements for a drone antenna. Specifically, the bandwidth is enhanced without increasing the substrate thickness. The proposed dual-mode antenna demonstrates one of the largest bandwidths (4% at 2.4 GHz and 7% at 5.2 GHz) on a thin substrate ( $0.0128~\lambda _{0}$ ) and presents one of the highest gain (~10dBi) in comparison to the published UAV antennas. It is shown that the antenna’s performance does not deteriorate for moderate bending conditions. Finally, a 3-element triangular multiple input multiple output (MIMO) configuration is designed and seamlessly integrated with the UAV body to demonstrate its efficacy.