Broadband Quasi-Yagi Antenna for WiFi and WiMax Applications

In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10 dB return loss bandwidth of this antenna is 50% operating from 2.3 GHz to 3.8 GHz. We obtain very flat gain (around 5 dB) over the entire bandwidth. For the design and optimization of antennas, we use HFSS CAD software from ANSOFT.

The Design of Circular Microstrip Patch Antenna by Using Quasi-Newton Algorithm of ANN

The paper presents the Quasi Newton model of Artificial Neural Network for design of circular microstrip antenna (MSA). In this model, a closed form expression is used for accurate determination of the resonant frequency of circular microstrip patch antenna. The calculated resonant frequency results are in good agreement with the experimental results reported elsewhere. The results show better agreement with the trained and tested data of ANN models. The results are verified by the experimental results to produce accurate ANN models. This presents ANN model practically as an alternative method to the detailed electromagnetic design of circular microstrip antenna.

Central Force Optimization with Gravity <0, Elitism, and Dynamic Threshold Optimization: An Antenna Application, 6-Element Yagi-Uda Arrays

This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Those extensions are Negative Gravity, Elitism, and Dynamic Threshold Optimization. The basic CFO heuristic does not include any of these, but adding them substantially improves the algorithm’s performance. This paper extends the work reported in a previous paper that considered only negative gravity and which showed a significant performance improvement over a range of optimized arrays. Still better results are obtained by adding to the mix Elitism and DTO. An overall improvement in best fitness of 19.16% is achieved by doing so. While the work reported here was limited to the design/optimization of 6- element Yagis, the reasonable inference based on these data is that any antenna design/optimization problem, indeed any Global Search and Optimization problem, antenna or not, utilizing Central Force Optimization as the Global Search and Optimization engine will benefit by including all three extensions, probably substantially.

A New Compact Omni-Directional Quasi-Self-Complementary Antenna for Wireless Communication Systems

This article describes a new miniaturized omni-directional antenna with quasi-self-complementary structure for wireless communication applications. A novel ground structure composed of five rectangular plates is proposed to enhance the impedance bandwidth and reduce the antenna size. The proposed antenna is comprised of two patches surrounded by the ground structure. Two metal patches of the antenna are located on two opposite sides of the dielectric substrate. The feed patch is used to excite the radiation patch. This unique design is realized by properly choosing the suitable feed patch shape, selecting similar slot shape on the radiation patch, and tuning their dimensions. The proposed antenna with an extremely small size of 6 mm × 9 mm has an operating impedance bandwidth ranging from 4.5 to 6.1 GHz for S11 < -10 dB, which also covers the two IEEE 802.11a wireless local area network bands (5.15 - 5.35 GHz and 5.725 - 5.825 GHz). In addition to be very small in size, the antenna exhibits omni-directional radiation patterns in the entire operating bandwidth and low cross polarization. The distortionless time domain performance of the antenna is confirmed by investigation of the phase response and group delay. The obtained results in both frequency and time domain show that the proposed antenna is suitable for use in wireless communication systems.

基于特征模理论分析的超宽带小型化准八木天线设计

文中设计了一款超宽带准八木天线。根据特征模理论对传统的准八木天线进行分析,并结合天线理论,在不改变天线原有尺寸的情况下,通过采用弯折、切槽等技术,增大了电流路径,拓宽了低频的工作带宽。天线尺寸为0.256λ_(0)×0.256λ_(0)×0.002λ_(0)(λ_(0)为最小工作频率所对应的波长),工作带宽为0.78 GHz~1.58 GHz。与初始天线相比,相对带宽从32.0%提高至67.8%。通过前后比可以看出,天线具有良好的定向性能,可以满足人脑探测活动的需求。

基于柱面波展开的准远场快速测量方法研究

为解决常规暗室环境不满足大口径天线的测量需求、测试系统复杂以及测试效率低等问题,文中对天线测量中的高效测量方法进行了研究,重点研究了准远场快速测量方法,提出了一种基于柱面波展开理论的准远场变换算法。该算法适宜在准远场距离下对一维电尺寸大而另一维电尺寸小的天线进行测量,提高了此类天线的测试效率和现有暗室的测试能力。为了验证所提出的方法,利用电磁仿真软件设计了三个均匀分布的线性阵列。仿真和实物测试结果验证了所提出方法的正确性。

基于增强型微带耦合器组的全双工自干扰消除方法

自干扰消除技术是实现同时同频全双工通信的基础。在现有全双工天线系统的基础上,文中提出了一种新型的基于增强耦合器组的自干扰消除结构,该增强型耦合器组采用多支微带耦合器作为结构单元,具有良好的阻抗匹配和相位平衡性能,可以在大带宽范围内(500 MHz)实现超过40 dB的收发隔离度(中心频点为2.4 GHz)。进一步结合抽头式自干扰消除电路和宽带式贴片天线,文中提出的天线域模拟域联合自干扰消除方案最终可在120 MHz带宽上实现超过50 dB的自干扰消除。

基于Quasi-Yagi天线结构的波导-微带背靠背过渡

提出了一种新颖的波导-微带线的背靠背过渡结构,利用Quasi-Yagi天线结构在波导E面与波导形成电场耦合,通过采用高介电常数基片和增加Yagi天线引向器阶数的方法,改善天线与波导的电场耦合效果,以达到在通频带内平稳过渡,较传统的波导微带过渡结构有着更宽的带宽(将近68%)。通过电磁仿真软件CST在整个X波段对其进行了全波分析,得到了较好的S21(S21<0.7 dB)。对这种过渡结构进行了容差分析,在10%的误差范围内S21仍能保持较好的一致性和相对低的插入损耗,能满足加工要求。

Improving Bandwidth of Yagi-Uda Arrays

A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.

On the Design of Planar Printed Dipole Array Antennas

In this paper, we propose a new design procedure for printed dipole array antennas. Applications of these arrays are devoted to wireless communication systems, mainly base stations and beam steerable antennas. All the designs have been developed at the frequency of 3 GHz. This structure is chosen in order to enhance the gain and minimize the backside radiations of an antenna array with a very simple feeding.

Modal Resistance of Spiral Antenna

This paper proposes a quasi-static conformal mapping analysis to analytically evaluate the input resistance of Archimedean spiral antenna at its radiation region. The deviation from the original constructs of band theory for two-wire spiral antennas leads to the concept of common slot-line mode radiation. The per-unit-length capacitance and the characteristic impedance of the quasi-TEM fundamental propagating mode in periodic coplanar waveguide (PCPW) structure are obtained in terms of spiral parameters including substrate properties. This formula enables little computational effort on the computation of input resistance at the radiation mode of balanced-excited two-arm Archimedean spiral antennas. The numerical simulation demonstrates the accuracy of derived formulas both in free space and when a dielectric layer is presented.

无源毫米波成像雷达准光路及聚焦天线设计

提出一种用于空中目标探测的无源毫米波雷达准光路和聚焦天线设计方法。对焦平面阵列实时成像探测系统中天线的聚焦特性进行了仿真,分析了天线的焦径比对天线聚焦特性的影响,研究了抛物面天线和偏置抛物面天线在馈源偏焦时天线波束的畸变情况。设计了聚焦天线的馈源阵列,对馈源阵列天线单元间的互耦进行了分析。探索了反射面支架对聚焦天线聚焦特性的影响。仿真分析的结果为无源毫米波雷达空中目标探测系统的准光路和聚焦天线设计提供了支撑。

电小准各向同性扇形磁偶极子天线

本文提出了一种电小准各向同性扇形磁偶极子的设计方法 .利用微带贴片天线模式综合设计方法,研究由不对称边界条件原型磁偶极子演化成的扇形磁偶极子,发现不对称边界条件情况下可以同时实现电小天线设计和准各向同性辐射特性.通过推导解析设计闭式而确定天线关键参数,设计了圆心角为300°的扇形磁偶极子,分别采用“同轴线+扼流套筒”和“开槽同轴线”两种馈电方式进行激励和测量.结果表明:采用开槽同轴线激励的天线可以获得最均匀的总电场方向图,其最大不圆度低于6.7 dB,辐射效率为91.2%,最终实现的准各向同性扇形磁偶极子的电尺寸为R=0.156λ_(g)×0.056λ_(g)(k_(g)a=0.92),满足电小尺寸条件.

基于FP腔准锥状波束天线研究

锥状波束天线在方位角上具有全向辐射方向图,在法线方向上具有凹口,由于通信传感面积大,广泛应用于无线通信、车载卫星通信等工程中。本文提出了一种基于Fabry-Perot谐振腔通过电控开关实现波束切换的准锥状波束天线。该天线以边缘8个超宽带天线和中心8个同轴进行馈电,通过FP腔提高天线增益,馈源从天线边缘和中心向FP腔馈电,利用电控开关和一分二功分器分别激励每组端口,每组端口在不同频率下于相同的方位角辐射波束,在3dB的交叉范围内,实现俯仰角7°~37°的波束切换覆盖。与传统的锥状波束天线相比,具有宽频带、高增益的特点,在通信系统中具有应用价值。

小型化准八木天线的仿真与实验研究

微带准八木天线具有端射的辐射方向图,设计方便,结构简单,其小型化是应用中面临的重要任务。文中针对S波段微带准八木天线的小型化技术开展了仿真和实验研究。首先,研究了基本型的印刷八木天线,在有源振子长度为50 mm和4个引向器的条件下,仿真得到驻波比小于2的频率为2.73 GHz,增益约为4 dBi;然后,在相同的有源振子横向尺寸和引向器个数条件下,采用振子曲折线技术,仿真得到驻波比小于2的频率为2.675 GHz,增益也约为4 dBi;最后,针对相同横向尺寸和引向器个数的曲折线振子,引入介质埋藏技术,对于不同厚度的高介电常数的介质基板覆盖,仿真了准八木天线的端口驻波比和辐射性能的变化情况,在介质基板的相对介电常数为9.8和厚度为8 mm的情况下,仿真得到驻波比小于2的频率为2.2 GHz,增益也约为5 dBi,方向图形状略有变化,对介质埋藏的曲折线振子八木天线进行了加工和测试,测试结果和仿真结果接近。研究结果表明,采用介质埋藏和振子曲折线技术均可以一定程度上缩减准八木天线的横向尺寸,其中介质埋藏技术效果更为明显,二者之间的结合是小型化准八木天线的有效方案,文中的研究为实际工程应用提供了技术参考。

一种微带准八木天线的改进设计

在Ramadan A.Alhalabi设计的准八木天线基础上进行了改进设计,采取增加展宽天线带宽的两个寄生贴片和振子耦合枝节和提高天线增益的天线背面引向振子组,减小天线体积的馈线结构等改进措施,从而达到展宽天线相对带宽的目的。使用Ansoft HFSS软件对改进天线进行仿真实验年和对实物天线进行测试,结果表明:这种改进型天线结构设计合理,其相对带宽都大于20%(VSWR≤2),在2.4GHz处的增益都大于10dB,天线具有良好的性能,从而拓宽了该准八木天线的应用范围,而且紧凑的结构和较小的尺寸便于天线组阵。

一种新型共形微带准八木天线的设计

设计了一种新型的用于柱面共形的微带准八木天线.天线共形在一段圆柱体表面,通过共面波导馈电,避免平衡不平衡转换,简化了天线结构.采用蝶形偶极子作为辐射源,增加天线带宽.采用分段结构引向器,提高天线增益,调节输入阻抗,达到匹配.实测结果表明:天线在790～1 080MHz频带内,回波损耗S11≤-10dB,相对阻抗带宽为30%,最大辐射增益为3.8dB.

一种基于容性加载的小型化准八木天线研究

在传统准八木天线的基础上结合小型化技术,提出了一种新型的小型化准八木天线.天线结构上,对天线的馈电结构部分进行合理布局减小天线的纵向尺寸;对反射器和馈源振子进行容性加载,增加电流路径长度,进而减小天线的横向尺寸.确定结构后,利用HFSS软件对模型的相关参数进行仿真优化.天线测试结果显示,在射频识别(Radio Frequency Identification,RFID)美标UHF频段902~928 MHz内实测结果与仿真结果吻合较好,其中增益为6.8dBi,驻波系数小于1.4,主瓣交叉极化比大于40dB.天线的尺寸仅为110mm×105mm,约为λ_0/3×λ_0/3(λ_0为中心频点自由空间波长),体现了小型化和优秀的电气性能.

准八木型宽带高增益微带天线

基于八木天线的结构设计并制作了一个准八木型宽带高增益微带天线，利用三维电磁仿真软件（Ansoft HFSS）进行仿真设计，在已有的单一引向器结构的基础上，通过增加引向器数量实现了高增益和较宽的带宽。实际测试表明：天线工作频段在4．8～6．4GHz，在中心频率5．6GHZ处，峰值增益约为10．2dB，前后比约为21dB，与仿真结果基本吻合。另外，还给出了准八木型高增益微带天线的设计过程，并对具体结构和参数的选择对天线性能的影响进行了比较和讨论。

小型化准分形加载单极子天线

提出了一种小型化宽带加载单极子天线,即对有顶部加载的单极子天线进行准分形和RLC集总加载。研究表明准分形可以有效地降低天线的谐振频率,提高辐射能力。准分形加载单极子天线和三维分形树单极子天线相比,结构非常简单,容易实现,和典型的加载单极子天线相比,天线的电尺寸要小得多。对准分形加载单极子模型天线进行了测试,实测结果和仿真结果比较一致。加入匹配网络后,可得到10:1的带宽。