Two-Dimensional Topology Optimization of a Horn Antenna

A two-dimensional horn antenna is used as a model for topology optimization. In order to employ the topology optimization, each point in the domain is controlled by a function which is allowed to take values between 0 and 1. Each point’s distinct value then gives it an effective permittivity, either close to that of polyimide or that of air, two materials considered in this study. With these settings, the optimization problem becomes finding the optimal distribution of materials in a given domain, and is solved under constraints of reflection and material usage by the Method of Moving Asymptotes. The final configuration consists of two concentric arcs of air while polyimide takes up the rest of the domain, a result relatively unsensitive to the choice of constraints and initial values. Compared to the unoptimized antenna, a slimmer main lobe is observed and the gain boosts.

Simplified Calculation Method for Transient Field of Transverse Electromagnetic Horn Antenna Used by High-altitude Electromagnetic Pulse Simulator

For conveniently calculating the radiated electric field of transverse electromagnetic(TEM) horn antenna,an approximate simplified analytical calculation method is suggested.This method divides the horn to a system of V-antennas and superimposes the fields of all V-antennas to obtain the field of the TEM horn.The method is compared with the traditional analytical method and numerical method.The obtained results suggest that the proposed method is valid,simple and that it can fastly calculate the radiated electric field of the TEM horn antenna in an arbitrary space with an arbitrary excitation voltage.Based on this method,radiation of the TEM horn antenna of a high-altitude electromagnetic pulse(HEMP) simulator is simulated.Rise time,pulse width,peak value of electric field,and field distribution are analyzed.Results show that the TEM horn antenna can be used in HEMP simulators: the near field waveform is closer to the standard waveform than to the far field waveform; the standards for the rise time and the peak value of electric field are easily satisfied; the pulse width of the radiated field can be increased by broadening the pulse width of an excitation source and by making the antenna of a proper

“天线与电波传播”课程中案例设计式教学的探索

“天线与电波传播”是电子信息类本科专业核心课程,是“电磁场理论”课程的深化与应用拓展。课程涉及诸多典型的天线,包括八木天线、平面螺旋天线、喇叭天线、微带天线等,天线结构较复杂,理论分析难度较大,大多需要近似分析。为了提高“天线与电波传播”课程的教学效果,针对典型天线设计较成熟的现状,在理论课程教学中采用案例设计式的教学方法,通过案例设计,让学生带着目标任务去学习,提升对“天线与电波传播”课程学习的兴趣和主动性。以矩形喇叭天线设计为案例,提出具体的矩形喇叭天线设计需求,学生运用所学的课程知识,通过运用电磁仿真软件进行设计,完成设计目标,增强获得感,并将理论的近似计算结果与仿真结果进行对比分析,深化学生理论与实际的联系。通过上述案例设计式教学,让学生由“接收天线”转变为“发射天线”,强化学生对课程知识的理解,增强学生的创新思维能力和综合分析能力。

小型化超宽带H面脊喇叭端射天线

超宽带天线技术是实现射频孔径综合的关键技术之一,适用于解决大型电子信息系统中采用多个天线带来的布局困难、互相干扰等问题。本文设计了一款具有端射特性的小型化超宽带H面脊喇叭天线。天线通过加载指数型脊结构,降低了矩形波导的截止频率,从而大幅展宽了天线工作带宽。同时,通过在喇叭口加载单曲面形介质透镜,改善了辐射口面上相位不均匀的问题,进而显著提高了天线的端射增益。该天线结构紧凑,其尺寸仅为0.57λ_(L)×0.45λ_(L)×0.11λ_(L),可覆盖0.8 GHz~18 GHz的超宽频带,且交叉极化优于30 dB。该天线剖面低、结构稳定、易于加工,可直接安装于金属结构上,易于与载体集成。通过与同类型端射天线相比可知,该天线在小型化和电性能两方面都具有优越性。

基于TEM喇叭的电磁脉冲辐射天线优化设计

针对TEM喇叭天线终端反射大、低频辐射效率低的问题,对其进行了仿真优化设计。采用时域分析方法,分析了端部加载电阻与背部加载电阻的低频补偿方法,对TEM喇叭天线的尺寸、极板顶角等结构参数进行了优化,采用末端卷边结构,提升了辐射场的峰值场强与脉宽。根据仿真优化结果,研制了长度2.5 m、天线极板间张角45°、天线极板顶角45°的TEM喇叭天线,通过实测验证了仿真结果。结果表明,加载电阻可以有效降低反射,背部加载电阻方式的峰值场强和脉宽比端部加载电阻高,且采用4个电阻并联加载的效果较好;适当增加天线长度、极板顶角以及极板间夹角可以提高天线辐射性能。该研究结果为TEM喇叭天线在辐射式核电磁脉冲试验系统的应用提供了参考。

一款高增益双脊喇叭天线

为了满足实际干扰测试需求,设计了一款脊上开槽的超宽带高增益双脊喇叭天线。首先,首次引入二次Bezier曲线作为脊的渐变曲线并验证了该曲线的可行性,天线的电压驻波比(VSWR)带宽为2 GHz~18 GHz;然后,通过加入楔形块和采用锥形渐变脊,成功地解决了天线高频增益下降和辐射方向图畸变的问题;最后,通过在脊上开锥形槽,进一步降低了低频段的VSWR。仿真结果表明天线在2 GHz~18 GHz内的VSWR小于1.9,在5 GHz~17 GHz内小于1.5,且在不加载介质透镜的情况下,高频增益稳定在18 dBi以上。实测结果表明天线的VSWR和增益与仿真结果吻合,可用于天线干扰测量系统和高增益反射面天线的馈源。

一种表面波衰减率测量方法研究

介绍了雷达吸波材料表面波衰减率的重要性以及测量方法,从雷达方程入手分析出近场条件下测量雷达散射截面(RCS)的各影响因素,通过分析得出发射天线和接收天线的波束宽度和间距成为近场测量RCS的重要误差来源。提出了增大方向图1 dB波束宽度并减小发射天线和接收天线间距来减小测量误差的方案,设计制作了8~12 GHz圆锥喇叭天线,具有良好的圆对称性,1 dB波束宽度达到22°。组建了近场RCS测试系统,以金属立方体作为目标开展了测试系统验证试验,与理论值相比RCS曲线峰值之差小于0.5 dB,平均值之差小于0.2 dB,具有较高的测量精度。使用组建的近场RCS测试系统开展表面波衰减率测量试验,与紧缩场测量结果之差为0.38 dB,实现了近场条件下表面波衰减率的准确测量。

High-performance lens antenna using high refractive index metamaterials

In this paper, a high refractive index metamaterial （HRM）, whose element is composed of bilayer square patch （BSP） spaced by a dielectric plate, is proposed. By reducing the thickness of the dielectric plate and the gap between adjacent patches, the BSP can effectively enhance capacitive coupling and simultaneously suppress diamagnetic response, which significantly increases the refractive index of the proposed metamaterial. Furthermore, the high refractive index region is far away from the resonant region of the metamaterial, resulting in broadband. Based on these characteristics of BSP, a gradient refractive index （GRIN） lens with thin thickness （0.34/~0, where 2~0 is the wavelength at 5.75 GHz） is designed. By using this lens, we then design a circularly polarized horn antenna with high performance. The measurement results show that the 3-dB axial ratio bandwidth is 34.8% （4.75 GHz-6.75 GHz） and the antenna gain in this frequency range is increased by an average value of 3.4 dB. The proposed method opens up a new avenue to design high-performance antenna.

Deployable Antenna with Compact Ortho-mode Transducer and Feeding Systems

The compact ortho-mode transducer (OMT) and compact conical corrugated horn(CCCH) are used as feeding system of the deployable dual polarizing antenna in this paper.A new stricture of double-septum in main wave guide OMT is proposed. The finite difference method in time domain (FDTD) in combination with genetic algorithms(GAs) is used to analysis and optimize this new OMT. The experiment results show that the voltage standing wave ratio (VSWR) of this OMT and feeding system is less than 1.17 in bandwidth; the isolation between the ortho-mode ports is less than -40dB; the cross-polar level of the feed can reach -35dB and the length of the main waveguide can be reduced 50% at least.

ANALYSIS OF N-SLOT STRUCTURE CORRUGATED HORN

On the space harmonics technique general formulas are derived of the characteristicequation and the equivalent wall admittance of corrugated horns with N-slot structure(each periodhas N slots whose shape and depth may be the same or different).As an example,the calculatedradiation patterns for a corrugated horn having dual-depth corrugations show good agreementwith the measured ones.

STUDY ON THE PHASE CENTER OF ELECTROMAGNETIC HORNS

The characteristics of the phase centers of electromagnetic horns having nearlysymmetric pattern are presented analytically.It is proved that the phase center on the φ=45°plane coincides with the average phase center,and if a single plane phase center is used to definethe horn phase center approximately,the φ=45° plane phase center will be the best choice.

Polynomial-Based Evaluation of the Impact of Aperture Phase Taper on the Gain of Rectangular Horns

The aperture phase taper due to quadratic phase errors in the principal planes of a rectangular horn imposes signifi-cant constraints on the on-axis far-field gain of the horn. The precise calculation of gain reduction involves Fresnel integrals;therefore, exact results are obtained only from numerical methods. However, in horns’ analysis and design, simple closed-form expressions are often required for the description of horn-gain. This paper provides a set of simple polynomial approximations that adequately describe the gain reduction factors of pyramidal and sectoral horns. The proposed formulas are derived using least-squares polynomial regression analysis and they are valid for a broad range of quadratic phase error values. Numerical results verify the accuracy of the derived expressions. Application examples and comparisons with methods in the literature demonstrate the efficacy of the approach.

基于改进遗传算法的车车直接通信毫米波喇叭天线研究

现有车载天线不适用毫米波通信系统,因此亟须研究适用于车车通信系统的毫米波天线。首先,对比现有喇叭天线的特点,确定圆锥喇叭天线为车载天线,通过等效源法求得天线的远场辐射方向图,根据设计要求确定天线的中心频率和增益;其次,基于传统经验公式和电磁仿真软件HFSS进行建模仿真,得到天线的特性参数,通过仿真结果对比得到喇叭天线的开口直径和波导尺寸对天线电压反射系数的影响;最后,利用改进遗传算法对天线进行结构优化,使得波导尺寸和开口直径参数达到最优。结果表明:在天线主频率下,优化后的天线增益为22.2 dB,电压驻波比为1.01,并有较好的方向性,满足车车直接通信系统中车载天线具有较高增益和较强端射能力的要求。

角锥喇叭天线高空电磁脉冲响应统计特性分析

[目的]旨在研究入射参量随机分布条件下电磁脉冲作用时角锥喇叭天线的耦合响应规律。[方法]首先,基于CST电磁仿真软件与Matlab软件联合仿真,建立角锥喇叭天线的电磁脉冲响应统计分析模型;然后,利用CST建立天线电磁脉冲响应仿真模型,通过电压驻波比、增益曲线来验证模型的合理性;接着,考虑通信系统在发射、接收等不同状态下的射频端口阻抗特性,在峰值场强50 kV/m的高空电磁脉冲(HEMP)照射下,得到天线端口耦合响应指标(包括开路电压、短路电流和负载电流等);最后,在球坐标系中设定方位角、仰角和极化角以服从均匀分布,并使用Matlab对天线负载响应波形峰值、波形能量等主要响应指标进行分布拟合。[结果]结果显示,主要信号指标概率分布大都呈“凸”字形曲线。以波形峰值为例,其响应波形峰值有90%的概率小于0.13 A,仅为最大峰值0.8 A的16.2%,即除了在特定的电磁脉冲入射范围内,角锥喇叭天线响应波形的各信号指标在大多数情况下都保持在较低水平。[结论]所得结果可为通信系统电磁脉冲易损性分析奠定基础。

X频段介质加载圆极化喇叭天线设计

设计了一款基于全介质极化器的X频段圆极化喇叭天线。该全介质极化器加载在线极化喇叭天线的前端,将线极化波转换为圆极化波,并有效辐射出去。同时,该全介质极化器还将天线的实测增益提高了约2 dB。天线的测试结果与仿真结果吻合较好。该天线在X频段(8~12 GHz)的实测S11均小于-10 dB,实测轴比在X频段内均小于3 dB,表明该圆极化喇叭天线具有宽带高增益特性。并且,该全介质极化器使用3D打印技术制作,具有加工简便、成本低的优点。该天线可应用于雷达、跟踪制导、卫星通信系统等领域。

一种具有近似对称E/H面波束宽度的SIW喇叭天线

本文提出了一种基于基片集成波导的喇叭天线。为了提高增益,在喇叭孔径前加载椭圆型介质透镜以调整辐射波的相位;为了提高带宽,在上述透镜的上下加载同样形状和厚度的介质板,不仅进一步改善与自由空间的匹配,同时还减小了E面方向图波束宽度,使得天线E/H面波束宽度近似相等。此外,通过在介质板上加载金属柱和金属条带减弱了后向辐射,并因此提高了天线的前后比。仿真结果表明,在S_(11)小于-10 dB的情况下,该天线的带宽范围为22.2 GHz至32.3 GHz,整个工作频带内增益超过9.6 dBi,同时实现了较高的前后比以及在E面和H面较为对称的辐射方向图。

具有高强度带外抑制特性的宽带双脊喇叭天线

提出了一种具有高强度带外抑制特性的宽带双脊喇叭天线。首先,采用两对喇叭外壁与双脊波导构成了开口波导结构,利用波导的高通特性实现高强度的带外抑制。然后,设计了一种非对称阶梯式双脊结构,基于脊结构降低喇叭主模截止频率的原理,获得较宽的工作带宽。仿真结果表明,提出的双脊喇叭天线在12~18 GHz内具有良好的阻抗匹配性能和稳定的方向图性能,通带内插入损耗小于0.5dB。同时,通带与阻带之间的过渡带很窄,传输系数在11GHz以下的频率范围内保持在-11 dB以下。所有结果表明,提出的双脊喇叭天线能够在保持良好的阻抗性能和稳定的方向图性能的同时,实现高强度的带外抑制效果。

大孔径全可动射电望远镜换馈系统设计

为了进一步满足探月工程、深空探测和其他天文观测任务的需求,对设计初期只配置了一个S/X双频馈源的昆明40 m孔径全可动射电望远镜进行升级改造,研制了其换馈系统。在不改变现有天线结构及光路的基础上,拆除了原S/X双频馈源,安装了新的S/X双频馈源,并增加了C频段、Ku频段馈源;给出了换馈系统的详细设计和实施方案,实现了3个馈源间自动快速可靠的切换。对馈源改造之后的天线性能进行了测试,结果表明,天线的主要性能指标有所提升。馈源及换馈系统改造之后,大孔径全可动射电望远镜具有多频段接收能力,能够完成更多频段的天文观测和深空探测任务,提高了望远镜的观测效率和科研产出。

一种用于毫米波双向通信的波导喇叭天线设计

毫米波由于方向性强,要实现在同一直线上的前后向通信,通常采用功分器+双天线的方式。为进一步实现集成化,本文提出了一款将波导功分器和双矩形波导喇叭天线进行集成设计的波导喇叭天线。首先,根据波导的两级阻抗变换设计T型宽带波导功分器;然后,根据最佳角锥天线公式完成对矩形喇叭天线设计仿真;最后,将波导功分器和双矩形形喇叭天线按工程应用进行集成设计建模仿真。仿真结果表明该双向天线最大增益为22.48dBi,在71-86GHz的频带内S_(11)优于15dB。除此之外,本次设计的波导喇叭天线具有结构简单、尺寸小、加工容易等优点,通过合理地集成到宽带通信设备中,可满足货运铁路准线性区上下行的双向无线接入。

交叉极化隔离度对射频仿真模拟精度影响分析

射频仿真系统可以通过控制四脊圆锥喇叭天线两路正交信号幅度和相位实现不同极化的模拟。但该系统存在交叉极化信号,将会产生极化模拟误差和两路正交极化信号角位置模拟偏差。为此,文中通过建立三元组辐射合成信号模型,分析不同交叉极化隔离度对极化轴比和极化倾角模拟误差的影响;同时,根据三元组角位置模拟模型计算不同交叉极化隔离度对两路正交极化信号角位置模拟精度的影响程度。分析结论可指导射频仿真系统工程建设。