一种新型类Vicsek分形多频天线的设计

在Vicsek结构的分形理论基础上进行了改进, 提出了一种具有良好空间填充性和自相似特性的新型类Vicsek分形天线, 并在接地板上引入缺陷地结构(Defected Ground Structure, DGS)来改善频率、抑制谐波, 得到了可以运用在无线局域网(Wireless Local Area Networks, WLAN)、全球微波互联接入(Worldwide Interoperability For Microwave Access, WiMAX)以及C波段卫星通信的四个频段.天线的谐振频率分别为2.45 GHz、3.46 GHz、5.8 GHz和7 GHz, 相应带宽为0.2 GHz(2.37~2.57 GHz)、0.49 GHz(3.2~3.69 GHz)、0.75 GHz (5.52~6.27 GHz)和0.56 GHz(6.68~7.24 GHz), 增益最高达到4.89 dB.天线的小尺寸及全向性辐射特性表明该天线能很好地满足便携式多频段移动设备的要求.     

Design and Analysis of Multiband Fractal Antenna for MIMO/Diversity Applications

In this article a modified hybridized fractal geometry i.e., fractal antenna is proposed for Multiple Input Multiple Output (MIMO) applications. These geometries are based on Minkowski curves and Koch curves located around the boundaries of the microstrip patch of rectangular-shaped patch. The hybridized model for fractal geometry is designed and analyzed on an FR4 substrate having a thickness of 1.47 mm for the Industrial, Scientific, and Medical (ISM) frequency band. But due to the proposed fractal geometry, it resonates at three bands (2.45 GHz, 3.67 GHz, and 5.88 GHz) and it is covering the ISM band from 2.42 GHz to 2.48 GHz with a VSWR value is 1.48. Further, a 2?×?2 antenna for MIMO application is proposed by considering identical antenna elements placed in parallel on the same substrate. MIMO antenna resonates at three frequencies as same as single antenna elements and covering the same operating bands. The two elements of MIMO confguration are simulated for various sets of distance values, and optimized distance is obtained 18 mm at which a proposed antenna provides low mutual coupling value, low Envelope Correlation Coefficient (ECC), and high diversity and peak gain. The calculated values of ECC and diversity gain are 0.0002 and 10 dB, respectively which satisfy the criteria of MIMO application. The design has been experimentally validated and an appropriate similarity of experimental and simulated results is achieved.

     

Low profile multiband rectenna for efficient energy harvesting at microwave frequencies

This paper presents the design and development of a multiband rectenna for ambient RF energy harvesting. The proposed rectifying antenna consists of fractal-based geometry to obtain GSM 0.9 GHz (0.8–1.2 GHz), GSM 1.8 GHz (1.6–2.1 GHz), WLAN 2.5 GHz (2.2–2.8 GHz), Wi-MAX 3.5 GHz (3.1–4.0 GHz), WLAN 5.5 GHz (5.3–6.4 GHz) and 7.35 GHz (7.0–7.8 GHz) resonating bands. The designed sensing antenna is low profile, lightweight and small in size with two circularly polarized bands at frequencies 1.8 and 2.5 GHz. In the proposed rectenna, a dual-stage voltage doubler rectifying circuit is utilized for converting surrounding RF signals into DC power. A matching network is connected between the fractal antenna and the rectifying circuitry for realizing a good impedance matching between them. To verify the proposed design, a prototype rectenna is fabricated and measured results are compared with the simulated results. The proposed rectifier provides an RF to DC conversion efficiency of 78%.     

CPW-fed circular slot antenna with slit back-patch for 2.4/5 GHz dual-band operation

A circular slot antenna fed by a coplanar waveguide (CPW) is proposed for dual-band operations. Dual frequency bands that cover the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) bands were obtained by embedding a pair of slits in the circular back-patch that is printed on the backside of the substrate and concentric with the circular slot. This design resulted in broadside far-field patterns with low cross-polarisation levels in both frequency bands and a small antenna size of 40/spl times/40 mm with the ground plane regarded as part of the antenna structure.     

一种新型共边矩形环嵌套的分形多频天线设计

提出了一种新型分形结构的天线,该分形结构由多个共用一条边的矩形环嵌套构成。由于结构的自相似特性,使天线能够在多个频段工作。研究表明,天线的通频带个数由分形结构的矩形环个数控制,且各谐振频点与相应辐射单元的尺寸密切相关。设计了能同时工作在蓝牙、WLAN和WiMAX频段的三频天线,天线仿真的谐振频点分别为2.44GHz、3.55GHz和5.59GHz,相应的带宽分别为7.0%(2.35GHz-2.52GHz)、15.0%(3.28GHz-3.81GHz)和30.1%(5.13GHz-6.95GHz)。实物的测试结果与仿真结果基本吻合,符合设计要求。     

一种双频左/右旋圆极化可重构环形缝隙微带天线

设计了一种频率比为1.9的双频左/右旋圆极化可重构环形缝隙微带天线,其在高频段和低频段分别工作于线极化和圆极化状态。在该天线中,环形缝隙和相互正交的四个缝隙臂将接地面分为五部分,缝隙臂上跨接两对PIN二极管开关和隔直电容。通过二极管开关的控制,天线在低频频率上可实现左/右旋圆极化的切换,在高频频率上则可保持其线极化性能不变。实验结果表明,天线在1.6 GHz的低频段上具有12.5%的3 dB轴比带宽,在3.06 GHz的高频段上其–10 dB阻抗绝对带宽为100 MHz,成线极化状态,辐射方向图近似不变。     

一种面向5G通信的宽带8单元MIMO天线设计

提出了一种面向5G的宽带8端口多输入多输出（multiple-input multiple-output,MIMO）天线.天线单元采用多枝节单极子结构,能够激发多模态,且能覆盖多频段.同时,采用弯折结构来实现小型化,且在相邻单元之间设计T形突出地结构来提高隔离度.仿真和实测结果显示,该天线在3~7.1 GHz内回波损耗大于10 dB,在3.3~7.1 GHz内隔离度高于15 dB.因为进行了有效的去耦,天线体现出明显的辐射分集特性,天线在目标sub-6 GHz频段内的包络相关系数（envelope correlation coefficient,ECC）接近0.在一8×8 MIMO系统中,计算得到的峰值遍历信道容量为43 bps/Hz,达到传统2×2 MIMO上限值的3.74倍.该8单元MIMO天线具有良好的分集和复用能力,能满足5G通信在sub-6 GHz的高速数据传输需要.     

一种基于分形结构的树生长微带天线设计

基于分形理论和自然树竞争(TGCA)思想,提出了采用树枝结构在不同生长因子下进行迭代生长的方法,对分形天线多谐振频率点进行优化控制,克服常见分形天线难于调整多个谐振频率点位置关系的缺点。树生长分形天线通过生长因子和天线尺寸的线性调整,可以方便地实现高低谐振频率的优化设计,方法简单易行。基于该方法,采用时域有限差分(FDTD)算法优化设计了一种具有GSM900/DCS1800双频谐振点的树生长微带分形天线。从实验和仿真结果可以看出,该微带分形天线在0.91 GHz,1.81 GHz谐振频率处带宽均大于100 MHz,水平方向为全向辐射,测量所得结果和仿真数据吻合较好,验证了采用生长因子调整分形天线谐振频率的方法。     

Development of PSO-ANN Ensemble Hybrid Algorithm and Its Application in Compact Crown Circular Fractal Patch Antenna Design

The traditional methods of designing antennas are not suitable in case of fractal antennas due to non availability of accurate mathematical design expressions. Recently, ANN model relating the physical and electromagnetic parameters of the fractal antenna to be designed is used as objective function of the optimization algorithm and it has been shown as an effective approach. In presented paper, ANN ensemble model has been used as the objective function of a PSO algorithm to calculate the optimal dimensions of a circular fractal antenna for desired resonant frequency. It has been established that ANN ensemble has better performance than the constituent ANN models. The design accuracy of the proposed hybrid algorithm is validated through the simulation and experimental results of the designed antenna. The size reduction capability of the proposed fractal antenna is used to design an antenna for 5.8 GHz WLAN band with a size reduction of 41.64% compared to simple circular microstrip antenna. The miniaturization of the antenna will lead to the design of compact devices for wireless communication systems.     

一种X 和Ka 波段频率可重构Koch分形振子天线研究*

将射频开关和Koch分形振子相结合,设计了一款结构紧凑的可工作于X和Ka两个波段的频率可重构天线,所设计的天线长度约为相同谐振频率普通振子天线的80％.天线工作于Ka频段时,由于天线中被射频开关断开的其它部分对其辐射性能的影响严重,会使Ka频段的方向图发生严重变形,因此我们又对天线进行了改进优化.改进后的天线由Koch分形振子和其前端另外延伸增加的一普通振子构成,改进天线在X频段和Ka频段的性能分别由Koch分形振子和普通振子所决定.仿真和实测结果表明:改进优化后的天线在X和Ka两个频段都具有良好的性能.     

On the design of CPW-feed diamond shape fractal antenna for UWB applications

This article presents the design of diamond shape fractal antenna with coplanar waveguide feed for ultra-wide bandwidth. This new fractal antenna has been designed on substrate ε_r ?=?4.3 and thickness h?=?1.53?mm. The antenna has been constructed incorporating fractal geometry in a circular disc of 30?mm diameter. The experimental result of this proposed antenna exhibits the excellent ultra-wide bandwidth from 2.05?GHz to 6.245?GHz. The detail parametric studies have been carried out using electromagnetic simulator HFSS10. The experimental results are in close agreement with the simulated results. The experimental radiation patterns are nearly omni-directional in H-plane and dumble shape in the E-plane throughout the frequency band of interest. The measured group delay of this antenna is stable throughout the band. Such type of antenna is useful for ultra-wideband communication system, microwave imaging and precision positioning system.     

Ka频段宽带圆极化微带天线

面向Ka频段高通量卫星对天线的需求,设计了一种Ka频段宽带圆极化微带天线.天线单元主要由圆形辐射贴片和缝隙耦合馈电结构组成,通过两个类T形缝隙结合实现宽带圆极化.天线仅有三层金属层,结构简单.仿真结果显示,天线单元的相对阻抗带宽为31.5%(25.1～34.5 GHz),相对3 dB轴比带宽为20.3%(26.5～32.5 GHz).由于单元尺寸较小,不便于对其性能进行验证,因此利用该天线单元组成2×2天线阵列,并进行加工测试.仿真与试验结果表明,天线阵列阻抗带宽以及3 dB轴比带宽可以覆盖25.6～33.1 GHz频率范围,实测结果与仿真结果一致性良好.     

Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed by Microstrip Line

A new design of a dual-frequency dual circularly-polarized slot antenna is presented. The dual-frequency is achieved using a single-layer microstrip-fed configuration coupled to a modified annular-slot antenna. The dual sense circular-polarization is obtained by four unequal linear slots which augment the annular slot. Experimental results show the proposed antenna has good circular polarization characteristics for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). The 10 dB return loss impedance bandwidths for the lower (RHCP) and higher (LHCP) bands are 26.7% and 11.3%, respectively. The 3 dB axial-ratio bandwidths are 6.1% and 6.0% with respect to 1.5 GHz (RHCP) and 2.6 GHz (LHCP), respectively.     

Compact Dual Band-Notched Monopole Antenna with Modified Radiating Patch for UWB Wireless Applications

Ultra-wideband (UWB) planar antennas with single or multiple notched frequency bands properties have recently been considered for various communications between wireless devices. In this study, a low profile microstrip monopole antenna with double band-filtering function is designed and investigated. FR-4 dielectric with properties of ε = 4.4 and δ = 0.02 has been employed as the antenna substrate. The configuration of the proposed design is composed of a modified fork-shaped radiating patch with inverted Ω-shaped slot and a pair of coupled Γ-shaped parasitic structures, a feed-line and a ground plane. The proposed dual band-notched UWB antenna provides good impedance bandwidth characteristic from 2.89 to 12.43 GHz for VSWR <2 with two notched bands which cover all the 5.2/5.8 GHz of WLAN, 3.5/5.5 GHz of WiMAX and 4-GHz of C bands ranges. The antenna provides good radiation behavior with sufficient gain levels over its operation frequency band.     

Metamaterial inspired quad band circularly polarized antenna for WLAN/ISM/Bluetooth/WiMAX and satellite communication applications

A CPW fed metamaterial inspired Quadband circularly polarized antenna is presented in this article. The proposed antenna consists of defected ground structure with a radiating stub, which is at opposite side of the feedline. A waveguide mode of analysis is carried out for split ring resonator (SRR) and complimentary split ring resonator (CSRR) to enhance the properties of metamaterials. The proposed antenna analysis is taken iteration wise and used FR-4 Material as the substrate material with Ɛ_r = 4.4 and analysed using ANSYS electromagnetic desktop. The designed antenna projecting the peak gain of 4.8 dB and it is working in the application bands of WLAN/ISM/Bluetooth at 2.4 GHz, 5.8 GHz and 3.35 WiMAX band, X-band downlink satellite communication system (7.25–7.75 GHz) and ITU band (8–8.5 GHz) with fractional bandwidth of about 70%. Proposed antenna exhibits circular polarization at 2.39–2.55 GHz, 3.05–3.1 GHz, 4–5 GHz and 6.3–6.64 GHz respectively. To know the signal integrity of the antenna, time domain analysis is carried out for identical antennas in two conditions (face to face and side by side) with the help of CST microwave studio. The designed antenna showing excellent correlation in measurements with respect to simulation results.     

Design and fabrication of a wideband reflectarray antenna in Ku and K bands

The purpose of this paper is design of a wide band single layer reflectarray antenna using a new broadband cell. The proposed cell consists of two parts. The first part is a circular patch and the second one is a ring with some additional stubs, which are attached to the patch and ring in a symmetrical form. The circular patch and ring elements are designed at frequencies of 20 GHz and 15 GHz respectively. In order to increase the reflectarray antenna bandwidth, at first the dimensions of the patch, ring and stubs are optimized to attain uniform phase response in the frequency range from 11 GHz to 20 GHz. Then an air layer is considered under the dielectric substrate. The reflectarray antenna is designed based on this optimized wideband unit cell. A wideband horn antenna is also designed as a feed antenna for the proposed reflectarray structure. The reflectarray antenna with horn are simulated. The 1 dB gain-bandwidth of 4.66 GHz is obtained (27.4% fractional bandwidth) in the frequency band of 14.72 GHz to19.38 GHz. Finally, the reflectarray antenna is fabricated and tested. It can be seen that there is a good agreement between simulation and measurement results.     

具有双陷波特性的六边形分形超宽带缝隙天线

提出一款具有双陷波特性的六边形分形超宽带缝隙天线,天线总尺寸为32 mmx16 mmx1.6 mm,采用六边形和三角形迭代嵌套的3阶分形结构作为辐射贴片,并采用缺陷地结构作为接地板,实现了3.0～ 15.26 GHz的超宽带带宽.在馈线两侧引入对称L形开路枝节,并在接地板上刻蚀U形窄缝隙产生了4.71～5.87 GHz...     

基于3D打印技术的宽带圆形微带天线

该文介绍了一款环形耦合的圆形贴片天线。采用圆形金属贴片作为天线的辐射贴片,通过在介质板上引入两个谐振环,产生两个新的工作谐振频段。通过调节圆形贴片和耦合环之间的高度,进一步拓宽了天线的工作频段。通过3D打印技术对不规则的介质基板进行加工制作,有效解决了传统加工方法加工难度大及生产周期长的问题。测试结果表明,该天线在3.8～5.8 GHz工作频段内,回波损耗小于-10 dB;在5.1 GHz时,天线增益达到8.4 dBi;天线相对带宽为42%,且具有良好的全向辐射特性。天线的测试结果与仿真结果基本吻合。     

可用于物联网的高隔离度双频MIMO天线

设计了一种高隔离度双频多输入多输出（MIMO）天线,该天线覆盖2.4 GHz和5 GHz无线局域网频带,可以应用于移动物联网之中。天线包含两个相同的辐射单元天线,采用微带馈电的方式进行馈电。单元天线使用单极子天线作为基本辐射器,其包含一根长的和短的单极子天线,分别谐振在低频和高频频段。通过在两个单元天线中间加载T型隔离器提高了单元天线之间的隔离度。天线的辐射振子、馈电以及T型隔离器都印刷在同一块微波板材上,从而方便了天线的制作和加工。仿真结果表明,该天线在1.9~2.8 GHz以及4.7~6.2 GHz频带范围内能实现良好的双频工作特性,天线隔离度近20 dB,可以广泛应用于物联网系统中。     

An Optimal Design of Fractal Antenna with Modified Ground Structure for Wideband Applications

This paper premeditates an optimal design of fractal antenna with modified ground structure for wideband applications. The proposed antenna has been designed by taking numerous iterations started from 0th to 3rd. To attain the wideband characteristics, the partial ground plane has been introduced in the 3rd iteration, and the length of the ground plane has been varied to enhance the bandwidth. The maximum value of bandwidth has been adorned in the final iteration as 1.88 and 0.20 GHz. Further, this bandwidth has been improved and embellished as 2.48 GHz within the frequency range of 3–6 GHz by employing horizontal and vertical extensions in the partial ground plane. Antenna is simulated by using HFSS and performance parameters of antenna like return loss (S_11?≤???10 dB), gain and radiation efficiency are in the acceptable limits. The maximum value of gain is reported as 5.1 dB and radiation pattern is also omnidirectional. The proposed antenna is useful for the wireless applications as WiMAX (3.4–3.69 GHz) and WLAN (5.15–5.35 and 5.72–5.82 GHz) Simulated and experimental results are also juxtaposed and found in good agreement with each other.