Radiation pattern synthesis for circular aperture horn antennas

A set of radiation pattern functions, suitable for synthesis of radiation patterns from circular aperture horn antennas, is obtained by assuming an aperture distribution consisting of the fields of cylindrical waveguide modes. A technique is presented for using a linear combination of the radiation pattern functions to approximate a desired radiation pattern. Linear combinations of the radiation pattern functions resulting in maximum secondary gain, when used to illuminate a paraboloidal antenna, are obtained empirically. Using spherical wave theory, maximum performance theoretically obtainable from an antenna is derived as a function of the aperture size of the feed system; the feed efficiency resulting from these theoretical limits on performance is compared to the feed efficiency of patterns obtainable from circular aperture horn antennas, and to experimental results of attempts to realize optimum circular aperture horn patterns.     

Circularly polarized twisted loop antenna

A novel wire-loop antenna is introduced for circular polarization. By introducing a small gap at the middle of two nonradiating sides of a one-wavelength square wire loop, a 90/spl deg/ time-phase difference between the currents on the other two radiating sides can be achieved. Then by twisting the square loop to make the radiating sides orthogonal the necessary conditions are satisfied for circularly polarized radiation. The antenna yields nearly ideally circular polarization at broadside as well as excellent input impedance properties near the design frequency. The radiation pattern has a broad beamwidth and good rotational symmetry about the axis. For a demonstrator operating at 1 GHz, a 3-dB axial ratio was maintained over /spl plusmn/30/spl deg/. The mechanism of circular polarization is analyzed based on numerical simulation. Experimental results are presented to verify the theoretical predictions made.     

Circularly polarized circular sector dielectric resonator antenna

A circular sector dielectric resonator antenna (DRA) with circular polarization and a single feed is investigated and demonstrated. The design utilizes the radius to height ratio and feed position of the circular sector DRA to excite two resonant modes that are spatially orthogonal in polarization and in phase quadrature. Experimental results are provided for the design and these demonstrate that the circular sector DRA produces circular polarized radiation with axial ratio less than 3 dB over a 10% bandwidth     

W 波段圆极化微带阵列天线设计

本文分析和对比了W 波段圆极化微带阵列天线不同的馈电形式,完成了圆极化阵列天线的设计。由理论分析 和仿真结果可知,单元间等幅同相馈电有利于W 波段圆极化微带阵列天线的实现,其2x2 阵列天线仿真结果驻波小于2 的相对带宽为3.5%, 轴比小于3dB 带宽为2%,中心频点94GHz 时天线增益为12.2dB。该天线在军事领域具有广泛的应 用前景。     

A New Coupling Mechanism for Circularly Polarized Annular-Ring Patch Antenna

A novel coupling technique for circularly polarized annular-ring patch antenna is developed and discussed. The circular polarization (CP) radiation of the annular-ring patch antenna is achieved by a simple microstrip feed line through the coupling of a fan-shaped patch on the same plane of the antenna. Proper positioning of the coupling fan-shaped patch excites two orthogonal resonant modes with 90 phase difference, and a pure circular polarization is obtained. The dielectric material is a cylindrical block of ceramic with a permittivity of 25 and that reduces the size of the antenna. The prototype has been designed and fabricated and found to have an impedance bandwidth of 2.3% and a 3 dB axial-ratio bandwidth of about 0.6% at the center frequency of 2700 MHz. The characteristics of the proposed antenna have been by simulation software HFSS and experiment. The measured and simulated results are in good agreement.     

矩形腔十字裂缝天线

随着卫星移动通信技术的发展,一种能适合机载和地面移动载体卫星通信的天线越来越受到人们的青睐。该种天线应具有宽频带、圆极化和电扫描跟踪等特性,而矩形腔十字裂缝天线就是该种天线理想的辐射单元之一。基于矩量法分析,本文提出了计算矩形腔十字裂缝天线的数值方法,给出了天线单元的输入阻抗、增益和轴比等辐射特性的数值结果,进行了实验验证。验证表明,理论和实验结果有着很好的一致性。     

一种基于电调移相器的可重构天线

设计并实现了一种基于反射式移相器的极化可重构天线。该天线使用一对交叉摆放的领结型振子作为辐射单元,并在馈电网络中通过两路移相器调整双馈端口间的相位差实现线极化、左旋圆极化和右旋圆极化模式之间的切换。通过加载匹配枝节的方法扩展了反射式移相器的移相范围,提高了移相器的移相精度,降低了天线圆极化模式带内的轴比。所设计天线的中心频率为5.4 GHz,在线极化模式下10 dB 阻抗带宽为990 MHz,在圆极化模式下10 dB 阻抗带宽分别为760 MHz 和850 MHz,3 dB 轴比带宽分别为510 MHz和480 MHz。该天线在频带内具有稳定的波束方向图,其平均增益为5.3 dB,并且具有27 dB 的主极化-交叉极化隔离。最终的实测结果与仿真结果基本一致,表明该天线具有良好的性能。     

双频双圆极化北斗天线的设计

设计了一种的小型化的双频双圆极化微带天线。对两个工作于主模的正方形贴片,通过采用对角切角方法,在北斗卫星导航系统的S频段实现右圆极化。通过蚀刻不对称臂U型槽结构,在北斗卫星导航系统的L频段实现左圆极化与小型化。其相比对普通的圆极化天线尺寸减小了24%,使用HFSS进行仿真,仿真结果表明本天线可以达到北斗系统对天线的各项指标要求。     

矩形腔十字裂缝天线的研究

随着卫星移动通信技术的发展,一种能适合机载和地面移动载体卫星通信的天线越来越受到人们的青睐。该种天线要求具有宽频带、圆极化和电扫描跟踪等特性。矩形腔十字裂缝天线就是这种天线理想的辐射单元之一。基于矩量法的分析途径,本文提出了计算矩形腔十字裂缝天线的数值方法,给出天线单元的输入阻抗、增益和轴比等辐射特性的数值结果,并进行了实验实证。理论和实验结果有着很好的一致性。     

Analysis of rotationally symmetric arrays of apertures onconducting spherical surfaces

Rotationally symmetric arrays of circular waveguide fed apertures on conducting spherical surfaces have been analyzed. Representation of the outside electromagnetic fields in terms of spherical transmission line modes permits the array analysis to be viewed as a spherical waveguide junction discontinuity problem. The apertures, in general, carry dual polarized circular waveguide TE₁₁ modes. Two independent formulations-the unit cell method and the eigen excitation method, which take rotational symmetry into account-are developed and are checked against each other numerically for computational accuracy. These two formulations are analytically linked as discrete Fourier series pairs. It is seen that mutual coupling along the array decays more rapidly when the polarization of excitation is perpendicular to the array plane than when it is parallel to it. This analysis has been applied in the performance analysis of the dome lens phased array radar antenna     

基于印刷振子和微带贴片的双极化天线单元研究

该文基于互补天线的原理,研究了一种基于印刷振子和圆形微带贴片的双极化天线单元,其中印刷振子为电流辐射源,圆形微带贴片等效为磁流辐射源,它们分别组成了两个极化端口,在空间形成双极化的辐射场。采用全波电磁仿真技术对该天线结构进行了电磁仿真和优化设计,仿真结果表明,在工作频带范围内,所设计的双极化天线的隔离度达到22 dB以上,在主辐射方向的交叉极化电平低于-20 dB。加工了双极化天线单元并进行了测试,其电压驻波比、端口隔离度和交叉极化电平均满足双极化天线的技术指标要求,验证了该双极化天线设计的可行性。     

Electric tripole antenna for circular polarization

The feasibility of using the tripole antenna for circular polarization was experimentally investigated. Measured impedance and radiation patterns were in agreement with the predictions from the infinitesimal tripole model. For simultaneous operation in both senses of circular polarization the tripole antenna must be fed by a special separator network, preferably of the nonreciprocal type.     

新型强耦合宽带双圆极化阵列天线

空间飞行器由于受到动力和负载的限制, 需要尽可能使搭载的天线轻质小型化.文中提出了一种新型强耦合双圆极化轻质天线.天线单元采用H型缝隙耦合和增加寄生贴片方法, 提高了天线带宽.同时, 通过在辐射贴片、寄生贴片上开圆形槽, 以及金属反射板栅格化的处理, 明显地减轻了天线的质量.采用这种新型天线单元, 设计了8单元的宽带双圆极化阵列天线.仿真结果表明:该阵列天线的中心频率为433 MHz, 左旋和右旋圆极化的相对轴比(Axial Ratio, AR)带宽(AR < 3 dB)分别达到了24.4%和23.2%, 有效实现了小型轻质化宽频带双圆极化阵列天线.     

Cylindrical-rectangular microstrip patch antenna for circularpolarization

The circular polarization condition for a rectangular microstrip patch antenna on a thin cylindrical substrate is investigated. The theoretical study is based on the modal-expansion theory, which is valid for the thin-substrate case. Numerical results for the aspect ratio of the cylindrical-rectangular patch, the optimal feed point for minimum voltage standing wave ratio and the 3-dB bandwidth for circularly polarized radiation are analyzed. Effects of the curvature on the circular polarization condition are also discussed     

具有谐波抑制功能的多极化微带天线阵设计

本文提出了一种基于切换馈电网络的极化可重构微带天线阵。阵列单元采用正方形辐射贴片,利用微带线缝隙耦合进行馈电,通过在馈电结构中心加载短路柱,可获得宽带性能的同时,有效抑制偶次谐波。综合采用串联组阵和并联组阵技术,优化设计了一款2×2的天线阵列,将阵列端口分别与微带分支线耦合器及微带混合环相连,最终实现了水平和垂直线极化,左旋和右旋圆极化四种模式的切换。实验结果表明,所提出的天线在ISM频段2.4~2.5 GHz频率范围内获得了良好的匹配和多极化特性。该天线阵设计简单、易于操作,可潜在应用于无线通信系统中天线极化分集的场合。     

导电媒质包围的球形空腔内的圆环天线的特性

本文导出了导电媒质在被其包围的球形空腔中的圆环天线内产生的输入阻抗的公式。描述了导电媒质中天线辐射性能的定义。导出了圆环天线的辐射电阻公式。数值计算结果表明所得的两个公式收敛迅速,一般只需取第一项或前两项之和即可。探讨了这些数值与空腔半径等参数之间的关系。     

左/右旋圆极化可重构微带天线

设计了一种左/右旋圆极化可重构的微带天线。在矩形微带贴片的两条边上增加枝节,贴片与枝节通过PIN 二极管开关连接,通过控制PIN 二极管的通断来改变正交模式的相位差,使天线在同一个馈电点上可实现左旋圆极化（LHCP）和右旋圆极化（RHCP）的重构。该天线在（2800±10）MHz 的频率范围内驻波比小于2,轴比小于3dB。仿真结果与测试结果均验证了该方案的可行性。     

3种不同馈电方式的半球面螺旋天线分析

基于曲线基函数的矩量法分析了中心馈电、侧边馈电和顶端馈电的半球面螺旋天线的辐射特性。结果表明,半球面螺旋天线具有较好的阻抗特性和方向图特性,具有较宽的圆极化带宽。顶端馈电的半球面螺旋天线具有较宽的增益带宽,其辐射波束的角度比较宽。半球面螺旋天线具有更低的剖面,可以稳定地固定于反射板上,稳定性强,更加具有实际应用价值,在卫星通信领域有着巨大的应用前景。     

新型定向超宽带天线

基于圆片单极天线是一种结构简单的超宽带天线,研究了一种新型的超宽带天线,它将4个圆片单极天线垂直交叉放置作为馈源并采用平板反射面,实现定向以及双极化或圆极化特性。分析了2种变形形式:将平板反射器换为抛物面反射器,实现高增益特性;将圆片振子变形,实现更宽的低频端阻抗带宽。通过电磁仿真软件,计算了天线的S参量和辐射方向图随频率的变化规律。分析表明文中的天线对于传统的圆片单极天线有了有效的改进,实现了超宽带、定向辐射、双极化、圆极化、高增益等不同的特性,它们在卫星通信和移动通信中具有良好的应用前景。     

ETC用5.835GHz微带阵列天线的设计

设计了一种ETC用低旁瓣圆极化微带阵列天线,应用于电子收费(ETC)的路测单元(RSU)。为实现低旁瓣、圆极化的效果,对2个微带天线单元运用旋转与相位补偿的方法进行轴比改进,并以改进后的2单元作为辐射单元制作了一款基于道尔夫-切比雪夫幅度分布的微带天线阵列。经过仿真与实际测量,该天线具有很好的低旁瓣、圆极化的效果。该天线对于ETC系统以及其他类似的天线系统具有很好的理论与实际意义。