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

This 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.     

Triangular quad-port multi-polarized UWB MIMO antenna with enhanced isolation using neutralization ring

In this study, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices. The antenna structure consists of four triangular monopole elements and neutralization ring (NR) structures. The monopoles are back-to-back positioned in symmetrical and orthogonal arrangement. Therefore, they radiate towards four directions without interference, and thus the diversity performance is improved. A novel NR is formed by combining a rectangular ring and a straight line to reduce the mutual coupling due to interoperation of the elements. Each triangular monopole is fed by 50 Ohm microstrip transmission line (MTL) with a thin strip line for ensuring impedance matching. Antenna performance in terms of impedance bandwidth, current distribution, radiation pattern, peak gain and envelope correlation coefficient (ECC) is also investigated. The MIMO antenna system has 3.1–17.3 GHz impedance bandwidth, 1–5 dBi peak gain variation, less than 0.1 ECC. The results indicate that the proposed antenna has the characteristics of larger UWB bandwidth, high isolation by the NR structure, multi-polarization, uniform gain and quasi-omnidirectional pattern.     

Multi-Element Wideband Planar Antenna for Wireless Applications

A wideband, multi-standard MIMO antenna with hexagonal geometry and slot is proposed for DCS/PCS/LTE/UMTS applications while keeping the real time application at prime to provide high data rate, low latency, high capacity, non-line-of communication, and reliability with continuity. The designed prototype covers 1.64–2.50 GHz frequency band with percentage bandwidth of 41.55% and resonates at 2.1 GHz. The isolation of more than 10 dB is achieved in the 2:1 VSWR frequency band. The total bandwidth of the MIMO antenna is 860 MHz. The designed MIMO has peak gain of 5.4 dBi, ECC?<?0.06, radiation efficiency?>?88%, and total efficiency?>?71%. The TARC active bandwidth is 600 MHz with best excitation angles of 45°, 45° at ports. The hexagonal slot is used for the control of induced current for better isolation. The proposed MIMO antenna evaluates the SAR performance at resonant frequency for listening, holding, and watching positions, and is found under the required safety norms.

     

Compact CPW-Fed ultrawideband MIMO antenna using hexagonal ring monopole antenna elements

In this paper, a compact coplanar waveguide (CPW) fed ultra-wide band (UWB) multi input multi output (MIMO) antenna is proposed. The antenna consists of two antiparallel hexagonal ring monopole elements. Circular arcs shaped grounded stubs are used to enhance the isolation, both the arcs are connected through stub to make common ground. Tapering of the slots of CPW feed line at feed point, and grounded slots are introduced for impedance matching over UWB. The proposed antenna is fabricated and impedance bandwidth, isolation, radiation pattern, and gain are measured. Moreover, envelop correlation coefficient (ECC) results are given. Proposed antenna structure operates in the frequency range 3–12 GHz with a fractional bandwidth of 120% keeping isolation better than 15 dB. The antenna has a compact size of 45 × 25 mm².     

Triple band notched mushroom and uniplanar EBG structures based UWB MIMO/Diversity antenna with enhanced wide band isolation

Triple band-rejection MIMO/Diversity UWB antenna characteristics are described in this paper. Proposed antenna discards worldwide interoperability for microwave access WiMAX band from 3.3 to 3.6 GHz, wireless local area network WLAN band from 5 to 6 GHz and X-Band satellite downlink communication band from 7.1 to 7.9 GHz. Mushroom Electromagnetic Band Gap (EBG) structures helps to attain band notches in WiMAX and WLAN bands. Uniplanar plus shaped EBG structure is used for notch in X-band downlink satellite communication band. Decoupling strips and slotted ground plane are employed to develop the isolation among two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing current path length. Mutual coupling magnitude of more than 15 dB is found over whole UWB frequency range. The Envelope Correlation Coefficient is less than 0.02 over whole UWB frequency range.The variations in the notched frequency with the variations in mushroom EBG structure parameters are investigated.The antenna has been designed using FR-4 substrate and overall dimensions is (64 × 45 × 1.6) mm³.     

Design of Dual‐Band MIMO Antenna with High Isolation for WLAN Mobile Terminal

In this paper, we propose a dual‐band multiple‐input multiple‐output (MIMO) antenna with high isolation for WLAN applications (2.45 GHz and 5.2 GHz). The proposed antenna is composed of a mobile communication terminal board, eight radiators, a coaxial feed line, and slots for isolation. The measured ?10 dB impedance bandwidths are 10.1% (2.35 GHz to 2.6 GHz) and 3.85% (5.1 GHz to 5.3 GHz) at each frequency band. The proposed four‐element MIMO antenna has an isolation of better than 35 dB at 2.45 GHz and 45 dB at 5.2 GHz between each element. The antenna gain is 3.2 dBi at 2.45 GHz and 4.2 dBi at 5.2 GHz.     

Broadband Multiple Input Multiple Output antenna for sub-6-GHz 5G communications

This paper presents the design of a miniaturized broadband monopole antenna for 5G and Wireless Local Area Network (WLAN) applications in mobile handsets. The proposed monopole evolved from a rectangular geometry of size 12 × 5 mm. The slot and stub loading techniques are used to improve the impedance matching offered by the antenna. Furthermore, bandwidth broadening is achieved using lumped elements loaded onto the aperture of the antenna. The proposed miniaturized antenna exhibits a measured impedance bandwidth of 63.6% (3.0–5.8 GHz) covering the 5G spectrum allocations under sub-6 GHz and the WLAN services. The antenna elements are replicated along the sides of the mock mobile handset PCB to study the functionality of the eight-element MIMO antenna. The prototype MIMO antenna fabricated and tested in the laboratory offers a peak gain of 3 dBi and total efficiency greater than 72%. Owing to miniaturization, the spatial distribution of the antenna element provides a low envelope correlation (ECC) of less than 0.2 and good diversity gain (DG) greater than 7.8 dB. In addition, the mean effective gain (MEG), channel capacity loss (CCL), multiplexing efficiency (ME), and total active reflection coefficient (TARC) are evaluated and presented. The estimated MIMO metrics are within the desired range of operation and hence make the antenna suitable for a complex propagation environment. The prototype antenna is developed on a thin microwave laminate with low-loss characteristics and tested under laboratory conditions. The outcomes indicate that the proposed eight-element antenna can be applied to 5G MIMO communications.     

采用阶梯形微带馈线的高隔离度超宽带MIMO天线

提出了一种小型二端口超宽带(UWB)多输入多输出(MIMO)天线。该天线由两个相同的矩形单极子和缺陷地结构(DGS)组成,通过改进阶梯形微带馈电线,在介质基板底层和顶层添加H 形枝节,并在辐射贴片上添加矩形条,提高了天线的带宽和隔离度。实验结果表明:该天线在1~20 GHz 工作频带内的隔离度大于21 dB,包络相关系数小于0.02。实测与仿真结果相符,表明该天线适用于UWB MIMO 系统,且该天线结构紧凑,尺寸仅为22 mm×29 mm×0.8 mm,可用于便携式通信设备。     

Asymmetrical mirror imaged monopole antenna with modified ground structure for DBDP radiations

ABSTRACT

In this article, asymmetrical mirror-imaged monopole antenna comprises a rectangular patch with tuneable stub and supported with modified ground structure (MGS) is investigated. The proposed antenna is characterised for dual band dual polarised (DBDP) radiations and can operate at 2.45 GHz for Wi-Fi and WLAN systems (2.4–2.485 GHz) and 5.45 GHz for WLAN band (WLAN band: 5.2–5.8 GHz) with the corresponding polarisations. A rectangular patch integrated with tuneable stub and a pair of asymmetrical inverted L-shaped slots positioned at ground plane is responsible for circularly polarised higher band; while a parasitic patch is created due to slotting of a mirror-imaged stub from the extended ground plane which is accountable for lower frequency band. The fabricated prototype shows that the measured Impedance bandwidths (VSWR < 2) are 350 and 1770 MHz for lower and higher frequency bands, respectively. The measured axial ratio bandwidth (AR < 3 dB) is yielded as 1450 MHz centred at 5.44 GHz for higher frequency band. The peak gains are measured as 4.3 and 4.15 dB for lower and higher frequency band, respectively. For the prototype antenna, substantial 3-dB beamwidth is found along with good cross polarisation suppression.     

Design of a Compact Hexagonal Monopole Antenna for Ultra—Wideband Applications

This paper presents two design compact hexagonal monopole antennas for ultra-wideband applications. The two antennas are fed by a single microstrip line . The Zeland IE3D version 12 is employed for analysis at the frequency band of 4 to 14 GHz which has approved as a commercial UWB band. The experimental and simulation results exhibit good agreement together for antenna 1. The proposed antenna1 is able to achieve an impedance bandwidth about 111%. The proposed antenna2 is able to achieve an impedance bandwidth about (31.58%) for lower frequency and (62.54%) for upper frequency bandwidth. A simulated frequency notched band ranging from 6.05 GHz to 7.33 GHz and a measured frequency notched band ranging from 6.22 GHz to 8.99 GHz are achieved and gives one narrow band of axial ratio (1.43%). The proposed antennas can be used in wireless ultra-wideband (UWB) communications.     

A reconfigurable wideband MIMO antenna combines RF energy harvesting

This article introduces a novel and groundbreaking approach combining multiple-input-multiple-output (MIMO) technology with radio frequency (RF) energy harvesting. The proposed antenna consists of two semi-circular monopole antenna components, optimized with dimensions of 89 × 51.02 × 1.6 mm³, that share a common ground plane to achieve MIMO characteristics. A series of split-ring resonators on the ground plane significantly enhances the isolation between the two radiating components. Band-notched features are performed in the 3.5 GHz WiMAX and 5.5 GHz WLAN bands through modified C-shaped slots in the radiating patch and two rectangular split-ring resonators serving as parasitic devices near the feed line. The reconfiguration of band-notching is made possible by controlling the modes of the embedded PIN diodes. The two antenna elements maintain mutual coupling below −18 dB from 1.5–13 GHz, achieving an impressive 158.62% impedance bandwidth. The antenna's efficiency and gain experience significant drop, indicating effective interference suppression at the center frequencies of the notch bands, and its performance in MIMO systems is assessed through parameters including envelope correlation coefficient, port isolation, radiation patterns, efficiency, gain, and diversity gain. The simulated properties of the designed antenna closely align with the measured outcomes, demonstrating its reliability and consistency. Moreover, the article evaluates the antenna's potential for RF energy harvesting, achieving a maximum harvested energy of 4.88 V. This proposed antenna can be used in multiple applications, like wideband, band-notching MIMO, and RF energy harvesting. This proposed antenna is an efficient, reconfigurable wideband MIMO antenna with novel RF energy harvesting capability.     

具有双带阻特性的超宽带缝隙天线

设计了一款微带馈电的超宽带缝隙天线,整体尺寸仅有30 mm×30 mm×1.6 mm,在3.08～11 GHz范围内驻波比小于2,可覆盖超宽带频段.为了实现对WiMAX和WLAN频段的陷波,分别在地板和馈线上蚀刻不同缝隙,仿真结果表明:在3.2～3.7 GHz,5 ～5.9 GHz驻波比大于2,增益显著下降,而在通带内仍然保持良好的全向辐射特性和稳定的增益.该天线结构简单、性能优良,能广泛应用于超宽带通信系统中.     

具有双阻带特性的新型超宽带天线研究

通过在天线上开设不同形状和尺寸的槽,设计和制作了一种新型的采用微带馈电且具有双阻带特性的平面超宽带天线。通过HFSS对天线仿真并分析,总结出了槽结构参数对天线阻带特性的影响规律。仿真和实测结果表明,除阻带外,天线在3.015~13.27频带上的VSWR小于2,相对带宽达126%,在3.25~3.6GHz、5.15~5.825 GHz具有良好的阻带特性,较好地避免了系统与Wimax及WLAN之间的干扰。该设计天线在工作频段内具有很好的辐射方向性和增益,满足超宽带通信的需求。     

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

A 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 $0.13\mathrm{\lambda }\times 0.06\mathrm{\lambda }\times 0.01\mathrm{\lambda }$. 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 (>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.     

Bi-directional UWB MIMO Antenna for Superior Spatial Diversity,and/or Multiplexing MIMO Performance

In this paper, a two-element UWB MIMO antenna with bi-directional radiation pattern is designed for superior UWB MIMO performance. The designed antenna adopts asymmetric coplanar waveguide ground feeding. The proposed antenna ECC is lower than the ECC of its omni-directional peer antenna. Simulated and measured ECC is lower than 0.016 over the entire ultra-wide bandwidth (3.1–10.6 GHz). The isolation between elements of the designed antenna is 20–25 dB exceeding the average in recently published works. The designed antenna has a diversity gain of almost 10 dB and average multiplexing efficiency of 85% over the entire ultra-wide bandwidth. The antenna preserves radiation efficiency higher than 0.96 and gain 3 dB. The diversity performance of the proposed UWB MIMO antenna is proven through real rich-multipath indoor environment measurements. Stationarity of the elected channel is evaluated through 100 successive measurements separated by a 3-min period for 5 h long. The measured spatial correlation coefficients are much lower than 0.5 in different scenarios.     

Miniaturized six-ring elliptical monopole-based MIMO antenna for ultrawideband applications

This paper proposes a miniature two-element Multiple Input Multiple Output (MIMO) antenna dedicated to UWB applications. The proposed MIMO design has a very low profile of 30 × 20 × 1.6 mm³. The proposed antenna is carefully designed and optimized using HFSS simulation software. As a proof of concept, the proposed design is realized and experimentally tested for MIMO applications. The proposed structure, printed on an FR4 substrate, comprises two symmetrical elliptical conductive patches on the upper side and a modified ground plane on the lower one. Each radiating element includes six elliptical rings. The modified ground plane consists of a T-shaped strip and two semielliptical slots etched opposite the feed line. All the parameters of the design are carefully optimized to achieve an ultrawide bandwidth antenna spanning from (136.08%) 3.1 to 16.3 GHz. The results are discussed and analyzed in terms of bandwidth, gain, efficiency, radiation pattern, diversity gain, envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and mean effective gain (MEG). All simulated results are found to be in good accordance with experiments. The design reveals attractive features for UWB applications. A good isolation (17 dB) between the two radiators is achieved despite the close proximity using the suggested ground plane geometry.     

A printed monopole ellipzoidal UWB antenna with four band rejection characteristics

An antenna design with four band rejection characteristics for UWB application is demonstrated. The proposed unique UWB antenna has shape of an embedded ellipse at top of trapezoidal patch (named as ellipzoidal), 50 Ω impedance microstrip line feed and a truncated beveled ground plane. To realize four band stop characteristics, three inverted U-shaped and a single I-shaped slots each of half guided wavelength are utilized on radiating element. The fabricated antenna has dimensions of 27 mm × 36 mm × 1.6 mm. This four band notched ellipzoidal UWB antenna has measured frequency bandwidth 2.8–14 GHz for magnitude of S₁₁ < −10 dB level. The measured ellipzoidal antenna exhibits four band rejection characteristics for magnitude of S₁₁ > −10 dB at 3.55 GHz for WiMAX band (3.26–3.9 GHz), 4.55 GHz for ARN band (4.35–5.05 GHz), 5.7 GHz for WLAN band (5.5–6.65 GHz) and 8.8 GHz for ITU-8 band (7.95–9.35 GHz). The proposed ellipzoidal UWB antenna maintains omnidirectional radiation pattern, gain, linear phase response, <1 ns group delay, and transfer function in the whole UWB operating bandwidth except at notched frequency bands.     

一种具有陷波特性的多模态频率可重构UWB天线

为了应对在超宽带(Ultra-Wide Band, UWB)系统中频率可重构天线尺寸偏大、模式单一等问题,提出了一种具有陷波特性的多模态频率可重构UWB天线。该天线通过在圆形单极子的辐射贴片上添加T型枝节和刻蚀I型槽、倒U型槽,以获得UWB覆盖范围为2.7～11.6 GHz的宽阻抗带宽,并产生四个陷波带。仿真与实测表明：控制PIN二极管的偏置状态,可以实现单频段、双频段、三频段、四频段和五频段共五种频段下八种工作模式的多模态切换。此天线大小为16 mm×19 mm,较传统单极子天线体积减小了40%以上,实现了小型化。天线的最大增益为4.13 dBi,具有良好的辐射特性。     

Printed Planar Monopole Antenna Design for Ultra-Wideband Communications

This paper presents an ultra wideband (UWB) planar printed monopole antenna fed by microstrip line. The antenna configuration contains a beveled ground plane. The beveled partial ground plane improves the impedance bandwidth. The measured frequency response demonstrates that the fabricated antenna exhibits an impedance bandwidth of 7.9 GHz over 3.1 to 11 GHz for VSWR < 2. The proposed antenna has ultra-wideband characteristics with omnidirectional radiation pattern and stable gain. Ultra-wideband performance of the proposed antenna is examined through the simulated surface current distributions. Measured results confirm that the antenna is suitable for UWB applications due to its compact size and high performance characteristics.     

利用贴片天线的奇偶模实现宽频带辐射零点扫描

设计了一款方向图分集的宽频带贴片天线。该天线由矩形贴片与共面波导馈电结构组成。贴片工 作在偶模或奇模状态,分别对应边射和水平全向辐射方向图。两个辐射模式由一个尺寸为35 mm×14. 5 mm 的馈电 网络激励。馈电网络中的微带线-槽结构和共面波导(CPW)结构分别产生同向和反向电场,从而分别激励贴片的奇 模和偶模,实现宽频带和高隔离。测试结果显示,天线的工作频段为2. 17~2. 95 GHz,工作带宽为780 MHz(31%)。 基于这两个辐射模式,天线可在特定角度产生辐射零点以对抗恶意干扰,且零点的角度随工作频率的变化呈线性变 化规律。该天线可用于MIMO 等智能通信系统。