改进型Sierpinski三角形分形多频天线研究

分形天线可以实现多频工作和尺寸减缩,在军用与民用方面都有着很大的发展潜力.研究了一种新结构形式的改进型Sierpinski分形天线,与普通结构相比,其可以通过调节各个三角形的高度比例来调整频比,且结构简单,加工制作更容易.仿真结果验证了改进型Sierpinski多三角形天线的多频特性.     

新型树状分形天线多频特性分析

提出了一种新型树状分形天线结构。通过对叶脉进行模拟,天线具有良好的多频特性 ,二阶分形天线可以在3个频带内良好工作。给出了天线回波损耗、方向图结果。对各阶分形 天线进行了加工与测试,仿真结果与测试结果基本吻合,为多频天线的设计提供了新的思路 。     

分形天线的应用研究

分形几何具有重要的特性即自相似特性,可以成功地应用于天线设计。该文主要介绍分形的基本概念,回顾分形天线的研究进展情况,并对现有的分形天线振子、分形天线阵的特性进行比较,探索未来分形天线的发展和研究方向。     

分形天线的特性与应用

分形天线是分形几何和天线技术交叉的产物。与传统天线比较,在性能保持相近的情况下,它表现出两个突出的优点:能够在多频段下工作、可以缩小天线尺寸。本文以Sierpinski Gasket天线为例,介绍了它的多频段特性;以Koch分形天线为例,说明了分形天线在缩小天线尺寸方面的优势。介绍了分形天线在UHF频段的应用现状,指出了进一步研究分形天线需要解决的若干问题。     

一种新型大频差多频段分形天线研究

提出一种新型大频差多频段分形天线,天线结构为在蝶形天线两臂上加载多个经优化后的开口矩形环缝。新型天线不仅可获得超过4.5∶1的大频差,而且能同时工作于4个频段。仿真和实测结果表明,新型天线4个频段都具有良好的性能。新型结构的提出丰富了分形天线的种类,为实现高性能的多频段大频差天线提供了一种可行结构。     

RFID分形阅读器天线设计

研究了不同阶数的Minkowski分形微带贴片天线的性能,给出了一种双层2阶Minkowski分形阅读器天线,仿真结果表明,天线在谐振频率点处具有良好的性能,且尺寸大小为30mm×30mm,与普通的方形贴片天线相比,其面积大约减少了43．75％,宽度减少了25％,具有较好的尺寸缩减特性,天线的性能和尺寸能满足手持RFID阅读器的要求。该天线设计具有结构简单、易于制作等特点,适合用于RFID阅读器天线的小型化设计。     

偶极子分形天线的驻波特性

提出一种新型偶极子分形天线，给出该分形天线的驻波曲线，同时讨论自相似性与驻波频段的对应关系及该分形天线与其对应的偶极子天线的驻波变化关系。     

Sierpinski分形天线特性分析

Sierpinski分形天线的结构具有自相似性,从而天线具有良好的多频带特性。文中主要研究了Sierpinski分形天线频带位置随天线张角和比例因子变化的一般规律,并简要的分析了Sierpinski分形天线阵,绘出了其远场方向图,讨论了其低副瓣特性。     

分形天线的特性分析及其在MIMO天线中的应用

分形最基本的特征是自相似特性与分数维,可以很好地应用于设计天线.与传统天线相比,在性能保持相近的情况下,分形天线表现出两个突出的优势:减小天线尺寸和使天线在多频带下工作.文中以Koch天线、分形树天线和分形环天线为例,说明了分形天线减小天线尺寸的优势;以Sierpinski基垫天线为例,说明了分形天线增加天线工作频带的优势.还对Minkowski分形天线阵列进行了分析,表明作为天线阵列单元的分形天线,可以提高天线阵的辐射特性.文中提出了将Minkowski分形天线应用于多输入输出(MIMO)天线中.     

用于多频通信的微带分形贴片天线

本文分析了一种新型的方形微带分形贴片天线,天线为Sierpinski毯的形式,可工作于三个频段。对此天线采用基于有限元法的软件作了理论分析,并做出实物进行了实验测量。此天线在无线、卫星和移动通信应用中很有前途。     

On the design of square shape fractal antenna with matching strip for UWB applications

This article presents the design of ultra wide band (UWB) square shape fractal antenna with matching strip. The impedance matching of this proposed antenna is achieved using the metal strip in ground plane at angle 60° from the centre of the patch. The experimental results of this antenna exhibit the ultra wide band characteristics from 2.355?GHz to 15.0?GHz corresponding to 145.722% impedance bandwidth. The proposed antenna has been simulated using 3D-Electromagnetic software. The experimental and simulated results are in good agreement. The measured radiation patterns of this antenna are nearly omni-directional in H-plane and bidirectional in E-plane. This antenna can be useful for transmission of high data rate wireless communications, medical imaging and other UWB applications.     

Split ring resonator based multiband hybrid fractal antennas for wireless applications

In this paper, initially two Moore Antennas are designed which are different from each other in terms of 50 Ω microstrip transmission line only. Same size Feed line is applied at right and left side of the substrate and termed as Left Side Feed Line (LFL) and Right Side Feed Line (RFL). To improve the multiband behavior of Moore Antenna, it is being fused with Koch curve and resultant antenna is named as Moore – Koch Hybrid Fractal Antenna (MKHFA) where Koch curves are superimposed on Moore curve. Two distinct MKHFA’s are designed as MKHFA with LFL and MKHFA with RFL. In order to attain the more number of frequency bands, improved gain, better impedance matching and improved bandwidth, both the MKHFA’s are loaded with Split Ring Resonator (SRR). Proposed antennas are designed on FR4 glass epoxy substrate with thickness 1.6 mm, relative permittivity 4.4. Results of Moore Antenna has been compared with MKHFA and found that MKHFA exhibits multiband behavior. A comparison between unloaded MKHFA using LFL/RFL and loaded MKHFA using LFL/RFL has been made and found that later case exhibits better results in terms of increase in number of frequency bands, bandwidth enhancement and improvement in gain. Prototypes of proposed MKHFA using LFL loaded with SRR and MKHFA using RFL loaded with SRR have been fabricated and tested for their results. The comparison between the simulated and measured results have been done and found in good agreement with each other. The overall dimensions of proposed MKHFA using LFL/RFL loaded with SRR is 25 mm × 25 mm and can be useful for different wireless applications such as Bluetooth (2.41–2.49 GHz) for ISM band, IEEE 802.11 g/b (2.40–2.48 GHz), WiMAX (2.5–2.69 GHz), WLAN (5.15–5.35 GHz), X-band satellite communication (7.1–7.76 GHz). Proposed MKHFA using LFL loaded with SRR also reports peak gain 5.76 dB and bandwidth 770 MHz, whereas, MKHFA using RFL loaded with SRR confirms peak gain 8.56 dB and bandwidth 750 MHz.     

UWB天线的宽带化技术及其发展

在现代通信技术中,为了实现通信保密、排除干扰、提高通信效率等,超宽带系统得到了大力发展,然而,在一定程度上却受制于系统中超宽带天线的阻抗带宽。详细介绍了展宽天线阻抗带宽的4种方法,包括渐变阻抗方法、分形几何方法、微带天线开槽方法和非频变结构方法,其中分形几何方法由于其几何结构的自相似性使得其贴片电流分布具有自相似性,从而导致天线的多频点谐振,有效拓展了天线带宽。上述4种天线尽管作用原理互不相同,但在超宽带天线的工程应用中,研究者可将这些方法单独或同时应用于天线结构设计,使得天线既能保持良好的方向性和增益等性能,又能获得较大带宽。     

Design of compact fractal patch antenna for X/Ku/K-band applications

This paper presents a fractal-based compact new monopole antenna for wideband applications. The miniaturization has been achieved by incorporating Minkowski and Koch-snowflake fractals. The proposed antenna design is etched on top of Rogers RT/5880 dielectric material with a dimension of $8.10\times 8.10$ mm². The antenna is designed, analyzed, fabricated, and tested in the laboratory. The proposed geometry operates over a 8.62–22.40 GHz with fractional bandwidth (FBW) of 88.84% and VSWR is less than 2. The proposed monopole antenna exhibits nearly omnidirectional radiation patterns over the entire resonating band with a gain of 1–2.91 dBi and a radiation efficiency of more than 60.5%. Also, the measured results of the prototype make an excellent agreement with the simulated counterpart. Further, the antenna gives good time-domain characteristics. Therefore, the proposed miniaturized antenna can be used in X/Ku/K-band applications.     

A new ultra-wideband fractal monopole antenna

The paper focuses on the peculiar dynamic behaviour of the recently developed 8 mm² TO-220-packaged, high-voltage, double-interdigitated (or rwo interdigi-tation levels—TIL) GTO thyristor. This novel power device was rated under both slightly and heavily inductive resistive loads, i.e. close to the real conditions encountered in practical power circuits employing GTO thyristors. Emphasis is laid on the ability of TIL GTOs to switch safely, with minimum power losses, a certain amount of anode current under high-voltage conditions and high commutation frequencies. The merits of TIL GTO thyristors are analysed in terms of their reliability and switching efficiency, which include the total power losses (conduction and switching losses), turn-on and turn-off gains and the switching speed. It is shown that thanks to their built-in self-protective features, these novel GTOs possess an enhanced current-handling capability at commutation frequencies up to 50kHz under extremely tough load conditions. The main implications of the results for power applications are outlined.     

加短路过孔的谢尔宾斯基毯式分形贴片天线研究

在传统谢尔宾斯基（Sierpinski）毯式分形贴片天线的基础上,加上两个短路过孔,使天线能够工作于更多的频段,并且在保持天线体积不变的情况下,使天线的第一频点降低到原来的一半。对所加短路过孔的位置和直径与天线的工作频点之间的关系进行了研究。使用高频电磁仿真软件（HFSS）仿真软件给出了天线S11和方向图的仿真结果,制作了实际的天线,给出了S11实验结果。实验结果与仿真结果基本吻合。     

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.     

基于分形的特异媒质层设计及应用于提高天线增益

根据分形原理,设计了一种新颖的分形图案。通过在印刷板(PCB)上周期性地蚀刻该分形图案制作了一种微带结构的特异媒质层。仿真计算表明,随着一些分形结构参数变化,该特异媒质层对电磁波具有连续变化的反射系数幅度和相位。依据部分反射层理论,将该特异媒质层加载在矩形贴片天线前方,在天线的工作频点、带宽和定向辐射特性基本保持不变条件下,矩形贴片增益得到不同程度提高。加工制作了特异媒质层和矩形贴片天线,测试结果验证了设计和仿真计算的正确性。     

Modeling of fractal antennas

Results on the numerical analysis of the Sierpinski and Koch fractal antennas are presented. It is shown that self-similarity of fractal structures affects electromagnetic properties of antenna structures created on the basis of these fractals. It is demonstrated that the Sierpinski and Koch fractal antennas are multiband structures; therefore, these antennas can be used for the development of radar and telecommunications systems. A technique is proposed for generation of an irregular determinate fractal structure that can be used for the development of a frequency-independent fractal antenna.     

一种二叉树状分形偶极子天线的设计

提出了一种基于二叉树状分形结构的分形偶极子贴片天线。该天线的介质基片采用相对介电常数为4.4,介电损耗角正切为0.02的FR4介质板,由微带线经阻抗变换后进行馈电。该天线利用分形技术实现了33%的尺寸缩减;通过平行双线结构和开U型槽技术,优化了阻抗匹配,降低了天线的谐振频率。通过仿真分析与模型优化,天线的最终尺寸为35 mm×22 mm×1.6 mm,中心工作频率为2.87 GHz,工作频率为2.77~2.97 GHz,-10 dB阻抗相对带宽为6.9%,工作频带内最小回波损耗可达-49 dB,最大增益可达2.36 dB。该天线具有小型化、阻抗匹配良好的优点,在当代小型化通信系统中具有良好的应用前景。