Element Multiple Input Multiple Output Antenna Research Articles

Low mutual coupling miniaturized dual-band quad-port MIMO antenna array using decoupling structure for 5G smartphones

Maintaining the compactness of 5G smartphones while accommodating millimeter-wave (mm-wave) bands presents a significant challenge due to the substantial difference in frequency. To tackle this issue, we introduce a miniaturized quad-port dual-band multiple-input, multiple-output (MIMO) antenna with low mutual coupling (MC) and a considerable frequency difference. This quad-port MIMO antenna, built on a Rogers TMM4 substrate, measures 17.76 × 17.76 mm2 and boasts a dielectric constant of 4.5. It incorporates four planar patch antennas, positioned at the corners in perpendicular orientations. For dual-band operation at 28/38 GHz, each antenna element features a rectangular patch with four rectangular slots, complemented by a full ground plane. The spacing between these elements is 0.5 λo, and we've included a decoupling structure (DS) to minimize mutual coupling (MC) among the MIMO antenna elements with minimal complexity and cost. Simulation and measurement results reveal a significant reduction in mutual coupling between the array elements, ranging from − 25 to − 60 dB. As a result, we’ve developed the envelope correlation coefficient (ECC) and made advancements in the total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG). The measured gains for this design are approximately 8.9 dBi at both 28 GHz and 38 GHz, with a radiation efficiency of nearly 93%. Furthermore, specific absorption rate (SAR) analysis confirms the MIMO antenna's suitability for smartphone handsets operating within the target frequency band.

SAR assessment of miniaturized wideband MIMO antenna structure for millimeter wave 5G smartphones

This work introduces a wideband two-element Multiple-Input Multiple-Output (MIMO) antenna array that covers the desired frequencies of 28/38 GHz for millimeter-wave (mmW) 5G smartphones. The antenna array demonstrates significant isolation and gain increase based on dual-mode planar dipole antennas. The proposed structure was designed using CST Microwave Studio 2019. The design is implemented on a Rogers RT 4003 substrate measuring 14.76 × 8.38 mm2 with a dielectric constant of 3.55. It features two planar dipole antennas positioned at the corners in a perpendicular arrangement to each other. To achieve the desired wideband performance, each element consists of a dipole antenna and a partial ground plane. The spacing between elements, including the parasitic element (PE), is set to 0.5λ₀ to increase isolation between the MIMO antenna elements while keeping complexity and cost to a minimum. Simulation results demonstrate an improvement in mutual coupling between array members, with measured values ranging from −55 dB to −75 dB. The envelope correlation coefficient (ECC) is also improved. Furthermore, enhancements are observed in the total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG). The measured gains of the proposed designs range from 6 dBi across the entire band to 10 dBi at 40 GHz, with a radiation efficiency close to 95%. The antenna performs well in the presence of the handset and human head model during simulation. The study identifies a safe and acceptable specific absorption rate (SAR) value, which provides a low SAR10g of about 0.963 W/Kg at 28 GHz and 0.583 W/Kg at 38 GHz. while maintaining superior efficiency and radiation patterns. When the antennas are constructed and tested, the experimental results surpass the modeling results. The simulation and test findings demonstrate a satisfactory fit within the target band, suggesting that the proposed structure could be applied to millimeter-wave 5G smartphones.

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.

High Isolated 10-MIMO Antenna Elements for 5G Mobile Applications

The enormous increase in gadgets has resulted in a data rate shortage insufficient to satisfy the user's needs. The multiple input multiple output (MIMO) technique is substantially deployed in the 5G wireless communication system to increase channel capacity and provide sufficient throughput. However, MIMO antennas are associated with mutual coupling, especially between closely spaced antenna elements, resulting in a low MIMO performance. Therefore, effective isolation techniques are essential to reduce the mutual coupling between the adjacent MIMO antenna elements. A hybrid decoupling technique of self-isolation and an orthogonal mode approach has been proposed to provide significant isolation for high MIMO order 5G mobile applications. A compact self-isolated 10 × 10 MIMO antenna system has been proposed for 5G mobile phone applications operating at the 3.5 GHz frequency band. The antennas act as radiating and isolating elements simultaneously, providing significant isolation. Furthermore, the self-isolated 10-MIMO antenna elements are printed on double side edges of FR-4 small substrates orthogonal to the system substrates, forming an orthogonal mode that enhances the self-decoupling approach. The s-parameters results indicate significant isolation of less than -19 dB between the adjacent 10-MIMO antenna elements. Likewise, the evaluation results of the MIMO performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity Loss (CCL), are less than 0.006, 9.97 dB, -10 dB, and 0.08 bits/s/Hz respectively. The isolation result and the evaluated MIMO performance metrics demonstrate that the proposed 10-MIMO antenna system is sufficient for 5G mobile applications.

Wideband self-isolated MIMO antenna element based on multiple adjacent modes coupling current cancellation for 5G mobile terminal application

Abstract In this article, a wideband self-isolated multiple-input multiple-output (MIMO) antenna element based on multiple adjacent modes coupling current cancellation is proposed for 5G mobile terminal. The wideband self-isolated technology based on multiple adjacent mode coupling current cancellation are demonstrated. With the combination of five adjacent loop modes, the −6 dB bandwidth of the proposed self-isolated element can cover 3.3–3.8 GHz and 4.4–5.0 GHz. Finally, an 8 × 8 MIMO array is constructed by arranging eight proposed wideband self-isolated antenna elements on the two long sides of the mobile terminal. Simulated and measured results show that the isolation of 8 × 8 MIMO array exceeds 15 dB without any decoupling structures in the operating frequency band. The proposed antenna elements are simply arranged to obtain a wideband high isolation MIMO array, and it is a good choice for 5G mobile terminal.

A review on techniques for improving mimo antenna performance in smart 5g devices

This paper presents the state-of-the-art literature on Multiple Input Multiple Output (MIMO) antennas for 5G systems. The degree of freedom offered by MIMO as a result of increasing transmitter and receiver elements has raised serious concern towards the impact due to mutual coupling between the adjacent elements in the MIMO antenna. Hence, this paper summarizes the various measures for suppressing mutual coupling between MIMO antenna elements. It also reports the methods for enhancing the bandwidth at the sub 6 GHz band by the deployment of different radiating structures and their influence over the crucial MIMO parameters. A study on the ways and means of handling the propagation losses at mm-wave frequencies by proper choice of PCB for fabrication is also discussed.

Mutual Coupling Effect and Reduction Method with Modified Electromagnetic Band Gap in UWB MIMO Antenna

In this paper, an effective technique for mutual coupling (MC) reduction between antenna elements of two multiple input multiple output (MIMO) microstrip patch antennas operating in the ultra-wide band (UWB) between 3.1 and 13.5 GHz is presented. The antenna array separation was kept at 44 mm for investigation, and the isolation was achieved through a modified electromagnetic band gap (MEBG) decoupling structure. The MEBG is embedded behind the radiating elements connected to the ground plane. HFSSv15 software was used to design and simulate the antenna. The effectiveness of the antenna and the MC reduction method was examined with and without the MEBG structure. The results revealed that the MC between the MIMO antenna elements was minimized when the MEBG structure was introduced. An MC of about −23 dB was obtained over the entire UWB frequency spectrum. This is more than a 10 dB improvement over the reference antenna (without the MEBG structure). Without limiting the effectiveness of the antenna when the MEBG structure was introduced, the results of the envelope correlation coefficient (ECC) gave the antenna a satisfactory diversity performance. The MEBG UWB MIMO antenna has an ECC less than 0.09 with a wide bandwidth. In addition, the total gain and the Voltage Standing Ware Ratio (VSWR) results were analyzed, which show that the performance of the antenna was not degraded while reducing the MC effect between the MIMO antenna elements.

Compact Tightly-Coupled Self-Decoupled MIMO Antenna Using Internal Hybrid Tunning

This brief offers a compact, tightly-coupled, self-decoupled vias-based multiple-input multiple-output (MIMO) antenna pair with a common ground for a 5G system. The projected design comprises modified T-shaped tightly-coupled antenna elements. It is effortlessly helping to achieve sound decoupling across the desired band without using any extra decoupling circuit between the elements. It is revealed that the structure of the self-decoupled MIMO antenna tunes the inductive and capacitive (hybrid) effect of elements, which helps to achieve the decoupling of antenna elements. A relevant equivalent circuit model for coupled and decoupled MIMO antenna is proposed to validate the insight operation of this proposed theory. The hybrid tuning among the MIMO antenna elements reduces the coupling effect mutually by modifying the antenna shapes. The proposed self-decoupled MIMO antenna pair demonstrates low mutual coupling across the 5G NR frequency bands: n48 and long-term evolution (LTE) band 42/52 (3.2–3.6 GHz) with good diversity characteristics. Moreover, the one proposed design structure can offer dual-band self-decoupling features. The proposed structure provides 3.2-3.6GHz and 3.95-4.115GHz frequency bands. This structure can be optimize further to achieve dual-band/ wideband resonance in the design.

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.

Four Element MIMO Antenna Systems with Decoupling Lines for High-Speed 5G Wireless Data Communication

A low-profile planar multiple-input multiple-output (MIMO) antenna consisting of four elements with isolation improvement is proposed for 5G mm Wave (24–40) GHz applications. Each radiating element of the MIMO antenna comprises of a microstrip-fed tilted spade-shaped radiator with four asymmetrical slots and a partial ground plane. The antenna is optimized to resonate at 35 GHz covering a wide impedance bandwidth from 23.9 to 40.1 GHz. Two cross lines are then loaded between the antenna elements to improve the isolation > − 30 d B . The MIMO structure with the decoupling lines is fabricated and tested. The measured results are in good correlation with the simulated results. Other MIMO performance metrics such as the envelope correlation coefficient (ECC), channel capacity loss (CCL), diversity gain (DG), and total active reflection coefficient (TARC) are examined, and the results are found to be satisfactory for the device to be used for mm-wave 5G MIMO applications. Also, the antenna’s performance metrics such as radiation efficiency, gain, and radiation patterns over the operating band are presented.

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.

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.

Printed Closely Spaced Antennas Loaded by Linear Stubs in a MIMO Style for Portable Wireless Electronic Devices

An easy-to-manufacture and efficient four-port-printed Multiple Input Multiple Output (MIMO) antenna operating across an ultra-wideband (UWB) region (2.9–13.6 GHz) is proposed and investigated here. The phenomenon of the polarization diversity is used to improve the isolation between MIMO antenna elements by deploying four orthogonal antenna elements. The proposed printed antenna (40 × 40 × 1.524 mm3) is made compact by optimizing the circular-shaped radiating components via vertical stubs on top of the initial design to maximally reduce unwanted interaction while placing them together in proximity. The measurements of the prototype MIMO antennas corroborate the simulation performance. The findings are compared to the recent relevant works presented in the literature to show that the proposed antenna is suitable for UWB MIMO applications. The proposed printed UWB MIMO antenna could be a good fit for compact portable wireless electronic devices.

360° angular coverage pattern and polarization diversities wideband circularly polarized multiple input multiple output antennas

This article presents a new design of six-element prism and eight-element cubic circularly polarized multiple input multiple output (MIMO) antennas exhibiting pattern and polarization diversity characteristics. The proposed antennas have 360° angular coverage. Each element of the MIMO antenna is radiating power in a different direction; antenna-1 radiates in −30°, antenna-2 radiates in 30°, antenna-3 radiates in 60°, and antenna-4 radiates in 120°. Antenna-5 radiates in 150°, antenna-6 radiates in −150°, antenna-7 radiates in −120°, and antenna-8 radiates in −60°.The radiation pattern can be directed in a specific direction by exciting the particular antenna element. It has wideband circular polarization in X-band (8.0–11.8 GHz). The proposed MIMO antenna element consists of pairs of mirrored monopole antennas facing each other are configured in the form of the prism and cube. The chance of mutual coupling is very high in both the configuration. A hollow copper cylinder is placed inside the prism and cube to reduce the mutual coupling. The isolation between the antennas is found better than −24 dB. The impedance matching bandwidth is 3.8 GHz (8–11.8 GHz), and the 3 dB axial ratio bandwidth is 2.69 GHz (8.01–10.7 GHz). The envelope correlation coefficient is less than 0.09, and total active reflection coefficient is less than −10 dB in a wide bandwidth. High isolation and uncorrelated radiation patterns between the adjacent elements make the proposed six-element and eight-element antenna a good candidate for massive MIMO antenna systems. The size of the antenna is 38.8 × 38.8 × 23 mm3, and this compact MIMO antenna is useful for X-band communication.

Split Ring Resonator-Based Bandstop Filter for Improving Isolation in Compact MIMO Antenna.

The ever-growing expectation for high data rates has led to the introduction of multiple-input multiple-output (MIMO) technologies to wireless connectivity. Such a system requires an MIMO antenna with high isolation. At the same time, the MIMO dimension should not be compromised for achieving high isolation. Thus, isolation techniques that do not allow an increase in dimension need to be fostered for MIMO antenna design. In this paper, a novel low-profile, miniaturized MIMO antenna with high isolation was developed considering a split ring resonator (SRR)-based bandstop filter as a decoupling network. The bandstop filter was designed with a unit cell split ring resonator structure and was deployed between two closely spaced monopole MIMO antenna elements to obtain isolation as high as 39.25 dB at 2.61 GHz. Two open-circuit stub lines were attached with the MIMO feeding network to achieve good impedance matching at resonance frequency. The proposed antenna exhibited a peak gain of 3.8 dBi and radiation efficiency of 84%. It had a low envelop correlation coefficient (ECC < 0.12), high diversity gain (DG > 9.95 dB), low mean effective gain ratio (MEG 1/MEG 2 < 0.05 dB), and low channel capacity loss (CCL < 0.042 bits/s/Hz) at resonance frequency. The overall antenna dimension was restricted to for its easy integration in compact wireless devices.

A novel inverted elliptical frustum shaped multi-band MIMO DRA with bandwidth and isolation enhancement

This paper presents the design and development of a two element MIMO (Multiple Input Multiple Output) antenna system designed using Elliptical frustum shaped DRA (Dielectric Resonator Antenna). In the proposed MIMO system, adjacent antenna elements are separated by0.29λ0.The archetype operates in the microwave frequency range 7.96–15.67 GHz giving a maximum isolation of 37.38 dB at 11.08 GHz frequency with a wide impedance bandwidth of 52.6%. Various diversity performance parameters like Envelope Correlation Coefficient (ECC), Diversity Gain (DG) are evaluated to understand the performance of the antenna under MIMO environment. Fabricated archetype is developed and good agreement is found between the simulated and measured results.

A Metasurface-Based MIMO Antenna for 5G Millimeter-Wave Applications

This work presents a 4-element multiple-input multiple-output (MIMO) antenna with a single layered metasurface array for fifth generation (5G) millimeter-Wave (mm-Wave) communication systems. Each MIMO antenna element is composed of a $1\times 2$ array with a corporate feed network. Moreover, a metasurface array structure consisting of $9\times 6$ Circular Split Ring (CSR) shaped cells is employed to improve the gain and isolation between the MIMO antenna elements. The proposed antenna system is realized using 0.787 mm thick Rogers RT Duroid 5880 substrate. The performance of the antenna is investigated in terms of s-parameters, radiation characteristics, and MIMO parameters. The antenna operates at the mm-Wave frequency band ranging from 24.55 to 26.5 GHz. The incorporation of the metasurface layer enhanced the gain thus attaining a peak measured gain of 10.27 dBi. Additionally, isolation is also improved by 5dB after the employment of metasurface. The investigation of MIMO performance metrics such as Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Channel Capacity Loss (CCL), and Mean Effective Gain (MEG) exhibits good antenna characteristics. The demonstrated radiation properties of the proposed antenna ascertain its suitability for the forthcoming 5G communication systems.

Mitigation of mutual coupling in 2 X 2 dual slant polarized MIMO antennas using periodic array of SRRs loaded with transmission line for LTE band 40

2 X 2 dual slant polarized multiple input multiple output (MIMO) antennas with reduced mutual coupling is presented for polarization and spatial diversity. The design of printed periodic array of split ring resonators (SRRs) loaded with horizontal strip transmission line is proposed to mitigate the mutual coupling among the MIMO antenna elements. An equivalent circuit model, characterizes the effect of coupling between the array of SRRs and the loaded transmission line, which together reduces the near field coupling between the adjacent antenna elements. The additional horizontal strip at the bottom is utilized to seek the return current path to the ground plane. Polarization and spatial diversity is achieved by utilizing dual slant 450 polarized antenna elements with eight independent channels. All four dual polarized antenna elements are designed to operate with a VSWR of <2 for (2.3-2.4 GHz) Band 40. Dual slant 450 polarization is achieved by utilizing two printed planar bow-tie antennas in orthogonal orientation. Measured and simulated results shows by incorporating periodic array of SRRs loaded with transmission line a considerable mutual coupling reduction of 25 to 50 dB is achieved in E-plane, H-plane, and D-plane over the required band 40. An isolation of 30 dB and an average gain of 7.5 dB is measured for dual slant 450 polarized antenna elements. MIMO performance metrics in terms of envelope correlation coefficient and diversity gain are also investigated.

Isolation Improvement in UWB-MIMO Antenna System Using Slotted Stub

Multiple-input multiple-output (MIMO) scheme refers to the technology where more than one antenna is used for transmitting and receiving the information packets. It enhances the channel capacity without more power. The available space in the modern compact devices is limited and MIMO antenna elements need to be placed closely. The closely spaced antennas undergo an undesirable coupling, which deteriorates the antenna parameters. In this paper, an ultra wide-band (UWB) MIMO antenna system with an improved isolation is presented. The system has a wide bandwidth range from 2–13.7 GHz. The antenna elements are closely placed with an edge to edge distance of 3 mm. In addition to the UWB attribute of the system, the mutual coupling between the antennas is reduced by using slotted stub. The isolation is improved and is below −20 dB within the whole operating range. By introducing the decoupling network, the key performance parameters of the antenna are not affected. The system is designed on an inexpensive and easily available FR-4 substrate. To better understand the working of the proposed system, the equivalent circuit model is also presented. To model the proposed system accurately, different radiating modes and inter-mode coupling is considered and modeled. The EM model, circuit model, and the measured results are in good agreement. Different key performance parameters of the system and the antenna element such as envelope correlation coefficient (ECC), diversity gain, channel capcity loss (CCL) gain, radiation patterns, surface currents, and scattering parameters are presented. State-of-the-art comparison with the recent literature shows that the proposed antenna has minimal dimensions, a large bandwidth, an adequate gain value and a high isolation. It is worth noticeable that the proposed antenna has high isolation even the patches has low edge-to-edge gap (3 mm). Based on its good performance and compact dimensions, the proposed antenna is a suitable choice for high throughput compact UWB transceivers.

Hexagonal shaped fractal MIMO antenna for multiband wireless applications

A hexagonal shaped fractal Multiple input Multiple Output (MIMO) antenna resonates to six different frequencies is presented. A dumbbell structure with hexagon shaped defected ground structure (DGS) is created in the ground plane. Two antenna elements sharing a common ground plane are positioned orthogonal to each other for better isolation. The antenna is designed, fabricated using FR4 substrate with 1.6 mm thickness and tested experimentally. The antenna provides high peak gain of 8.69 dBi at 8.33 GHz. The multiband MIMO antenna resonates for the frequencies 1.9 GHz, 2.9 GHz, 3.2 GHz, 5.0 GHz, 5.6 GHz and 7.74 GHz. Mutual coupling is better than − 20 dB and the peak gain of the antenna ranges from 3.2 to 8.69 dBi. The designed orthogonal two element MIMO antenna is suitable for GSM, PCS, WLAN and Wi-MAX wireless applications. Simulation work is carried out by ADS tool and fabricated antenna is tested with vector network analyser.