一种参数可调的八木天线的设计

在对传统八木天线分析的基础上,为提高天线使用的灵活性和工作带宽,设计了一种以2.4GHz为中心工作频率的参数可变的18单元八木天线。设计过程中利用VB软件设计了一款天线计算器,方便了天线尺寸参数的计算和优化调整,还使用HFSS软件搭建天线的模型,并对其中一种参数方案进行仿真优化。测量结果表明:在2.3GHz～2.5 GHz频率范围内,天线方向图较好,与仿真结果较为吻合,天线输入端电压驻波比和回波损耗较为理想。     

一种八木天线前向增益优化的改进处理方法

就文献中八木无线前向增益优化的单元间距微扰迭代法，提出了一种改进的处理方法，它采用Hallen方程和电流分布函数的殆全域多项式展开相结合的方法作为天线分析的基础，使得优化算法的数学表达更为简洁，尤其避免了半波振子作激励单元时繁杂的数学处理，简化了数值计算过程过程，而且矩阵维数增加不多。文中给出了天线分析部分的计算实例和结果比较。     

一种结构紧凑的八木-宇田圆极化天线

基于八木-宇田概念提出了一种使用多节印刷方环谐振器的紧凑型圆极化天线。该天线一共有8节(节与节之间有空气隔开):1个反射器,1个激励振子和6个引向器。局部接地的开槽贴片耦合器集成在激励振子的方环谐振器内部,以激励环形谐振器的2 个正交线极化基模,从而实现圆极化辐射。为了获得高定向性圆极化辐射方向图,采用印刷在底部介质板上的折叠方环作为反射器,并将6个方环作为引向器放置在激励振子的顶部。设计、加工并测试了一个工作在440 MHz 的原型天线,测试结果与仿真结果表现出良好的一致性。由于开槽贴片耦合器和折叠方环反射器的小型化,使该天线的横向尺寸仅为约l₀/4′l₀/4。     

三类手机天线辐射与SAR仿真对比分析

利用HFSS软件仿真对比分析了3款手机天线的电磁辐射特性,并仿真人体头部模型内的电场和整体的SAR分布的方向图。仿真对比结果表明,单极子天线对人体头部电磁辐射远小于环形弯曲天线和PIFA天线。     

采用新型馈电结构的双频宽带导航天线设计

基于新馈电结构,设计了一款覆盖全球四大卫星导航系统的双频宽带贴片天线。采用了一种四分八馈电线路,以8个同轴馈电探针两两相连的方式将两路天线馈电信号合为一路,有效简化了馈电网络的复杂性,同时保证了天线辐射的增益、带宽和轴比性能。该双频辐射贴片单元采用正八边形层叠式结构设计,并在每个天线单元边缘对称添加两组矩形调谐单元,有效增加了天线辐射的波束带宽。该双频天线单元在高频1.482~1.617 GHz（波束带宽155 MHz）和低频1.191~1.252 GHz(波束带宽61 MHz）频段范围内,都能保证良好的辐射增益;高低频的3 dB轴比带宽为-130°~130°,具备良好的圆极化性能。经实物样机对比测试分析,实测结果与仿真结果基本吻合。     

星载太赫兹辐射计天线系统设计与分析

设计了一套星载太赫兹辐射计天线系统, 分别由偏置大口径卡塞格伦反射面天线和前端准光学馈电网络组成, 可以实现300 GHz、380 GHz和425 GHz三个频率通道同步接收电磁波辐射信号.详细介绍了准光学馈电网络的设计原理以及馈电组件的设计过程, 通过仿真分析可以验证馈电网络的输出参数完全满足设计指标要求.还介绍了太赫兹辐射计天线模型的建立过程, 通过分析并计算各频率通道的远场辐射特性, 结果表明:天线系统具有高增益、高隔离度等良好的辐射特性, 其主要电性能参数, 如主波束效率、交叉极化水平等, 明显优于其他辐射计系统参数, 有效地验证了该天线系统设计方案的合理性与可行性.     

基于有限元方法的螺旋天线设计

研究了一种用于中短距离通信的螺旋天线,分析了螺旋天线特别是轴向模螺旋天线的基本电磁辐射特性,介绍了有限元方法的基本理论和数值计算过程,并结合有限元法对螺旋天线进行了设计、优化,仿真出该天线的电参数和辐射方向图,然后将设计的天线模型进行通信实验。实验表明圆极化的轴向模螺旋天线通信质量良好,完全达到设计要求。     

抗干扰天线及天线阵列研究

本文对抗干扰天线及天线阵列进行了研究,提出了一种小型化的微带贴片天线,并使用该天线单元进行组阵。文中提出的立体天线阵列的主天线单元实现了宽波束和在低仰角方向上增益的改善,能够满足工程应用的需要。     

单元方向图对阵列综合性能影响分析

在阵列天线综合问题中,传统方法假设各辐射单元各向同性且忽略互耦效应。工程应用中这些忽略会给计算结果带来较大的误差。本文首先建立了天线单元方向图对天线阵列性能影响的数学模型,对阵列指向精度、目标方向图赋形等问题进行了仿真对比分析。为了克服由单元方向图带来的误差,将阵中单元方向图代入优化过程中,算例表明该措施的有效性。考虑了阵列边缘单元辐射特性差异对阵列性能的影响。仿真结果表明在优化过程中考虑这些差异可以进一步提高计算精度。     

Monolithically integrated Yagi-Uda antenna for photonic emitteroperating at 120 GHz

A monolithically integrated photonic emitter using a uniplanar Yagi-Uda antenna is presented. By integrating a uni-travelling-carrier photodiode with the antenna, an emission of millimetre-wave signals with a power of 0.1 mW at the frequency of 120 GHz has been demonstrated experimentally     

Modelling Yagi-Uda antennas using point source approximation

A point source approximation is shown to be an efficient algorithm for calculating the near and far fields of Yagi-Uda antennas for the evaluation of the human radiation exposure zone boundaries. Results of a 12-element Yagi-Uda antenna compared to numerical electromagnetics code show that the modelled antenna field strength and front-to-back ratio were calculated to within 0.10 and 0.34 dB, respectively, while the occupational and general public exposure zone boundary distances were calculated to within 0.23 and 0.14 m, respectively.     

A method of accurate determination of azimuthal distribution of received RF power

In this paper, we introduce a method for the determination of directional distribution of received RF power, with angular resolution independent of receiving antenna radiation pattern. The proposed method is based on a series of measurements taken while rotating, at fixed predefined steps, a usual directional antenna of known radiation pattern on the azimuthal plain. It is proved that the resolution accuracy of the measurement method depends only on the angular step of the antenna rotation and it is independent of the antenna beamwidth. As a result of this feature, the proposed method allows the determination of the RF power angular distribution with fine resolution using a directional antenna of much wider beamwidth for the measurements. Copyright © 2001 John Wiley & Sons, Ltd.     

手机天线辐射与人头吸收率的仿真分析

利用HFSS软件仿真分析了PIFA手机天线的电磁辐射特性。为改善天线的性能,在原结构基础上添加了金属屏蔽板,研究了加入屏蔽板后天线性能的变化情况。通过HFSS仿真人体头部模型内的电场和整体的SAR分布的方向图,仿真结果表明,加入屏蔽体后人体头部的辐射电场和SAR分布明显减弱。     

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6.8 dBi,驻波系数小于1.4,主瓣交叉极化比大于40 dB.天线的尺寸仅为110 mm×105 mm,约为λ₀/3×λ₀/3（λ₀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.     

A secret story about the Yagi antenna

A hitherto unpublicized story about a note thrown away by a British soldier named Newmann in Singapore during World War II, which revealed to the Japanese that the Yagi-Uda antenna was being used by the British in radar systems, is related. The invention of the Yagi-Uda antenna and its practical use in Europe are briefly discussed, and the role of radar and the Yagi-Uda antenna in Japan's defeat in the Pacific discussed. The history of Newmann's note is recounted in detail, and portions of the note itself are reproduced     

An improvement of parasitic dipole array using suppressor elements

A novel configuration of parasitic arrays is introduced. The characteristics of the array in both forward and backward radiation are improved by using a new element, the suppressor. The suppressor elements are aligned parallel to a radiating dipole or to a conventional endfire array such as a Yagi-Uda array. Radiation in the unwanted direction is reduced by the suppressors, and the forward gain is effectively increased. Design of the optimum antenna parameters was achieved using the moment method, and results were compared to measured values, with good agreement obtained. New arrays were compared to well-designed Yagi-Uda arrays. A new array which is aligned with two broadside suppressors and with three endfire elements had an improved forward gain of 1.5 dB and a reduced backward gain of -4 dB compared to a conventional, well designed Yagi-Uda array with five endfire elements     

Log periodic Yagi-Uda array

The log periodic Yagi-Uda array is introduced in this paper. The concept used for extending the frequency bandwidth of the basic Yagi-Uda antenna by employing log periodic principles is presented; and its connection with the log periodic array with parasitic elements is established on the basis of the measured performance. The results of experiments on a log periodic Yagi-Uda dipole array show that the antenna characteristics of the basic antenna are preserved with frequency. Because of the mirror symmetry of the structure, it is shown that a log periodic monopole is realizable.     

计算抛物面天线支杆对方向图影响的简化方法

本文基于物理光学球面波展开法，提出一种计算抛物面天线支杆对其方向图影响的简化方法，文中导出了计入支杆散射的天线辐射方向图的解析表达式，并给出了支杆对其方向图旁瓣电平影响的计算实例，数值结果表明，本文所提出的新方法不仅计算结果精度高，而且所需计算机容量小，运算速度快，可应用于天线工程设计。     

A Compact Diversity Antenna for Handheld Terminals

The handheld terminals antenna should have a small size, sufficient gain and big bandwidth. In this paper, a compact planar inverted-L diversity antenna for handheld terminals is proposed. Three diversity antennas operating at 2.15 GHz are designed and the effect of important parameters of the proposed antenna is measured. The isolation is found to be better than 13 dB, the usable bandwidth is about 13%. Moreover, the measured radiation patterns are also obtained that the backward radiation is decreased.     

Terahertz Yagi-Uda Antenna for High Input Resistance

This paper presents the design of terahertz Yagi-Uda antennas with high input resistance. The proposed Yagi-Uda antennas can achieve much higher input resistance than existing THz antennas by using a full-wavelength straight-line dipole and a full-wavelength U-shaped dipole as driver elements. Current leakage into the bias line was minimized by applying photonic bandgap structures at the bias line. By designing the antennas on a thin substrate, end-fire radiation patterns with high antenna resistance can be obtained even when the substrate has a high dielectric constant. We expect that the proposed Yagi-Uda antennas can achieve increased terahertz output power by improving their capacity for impedance matching with a photomixer.