锥削分布圆形口径场的瞬态辐射

利用电磁脉冲的口径瞬态辐射场计算公式,针对锥削分布圆形口径的同相口径场及线性相移、平方律相移等非同相口径场情况,计算了辐射高斯脉冲时的E面能量方向图、半能量波瓣宽度及面积利用系数等参数。计算表明,对于锥削分布圆形口径场,其辐射场特性与口径面半径、激励脉冲宽度及口径面锥削分布指数有着密切的关系。     

有限接地板上圆口径辐射方向图的计算

利用等效原理和矩量法计算嵌在无限大金属板上圆形口径的辐射方向图,激励为ＴＥ１１和ＴＭ１１模,然后把该辐射场作为有限接地板边缘的入射场,利用ＧＴＤ法计算有限接地板对圆口径方向图的贡献,其中在焦散区及接近焦散区鞴要用等效磁流法计算有限接地板的影响,给出计算公式及计算例子,部分结果得到了文献的验证。     

偏馈抛物面天线方向图外场测试分析

基于口径场法,提出了地基偏馈抛物面天线方向图的数值计算模型,分别给出了自由空间和镜面多径反射情况下的偏馈抛物面天线方向图,分析了测试距离对水平和垂直方向图的波瓣分布和增益的影响;同时分别仿真了固定测试距离情况下,偏馈抛物面天线镜面反射方向图随仰角和高度的变化规律.外场测试结果验证了仿真模型的正确性.该仿真模型能解释不同测试条件下,天线外场方向图的波瓣分布特点,对天线外场测试设计、性能评估和测试误差分析有一定的指导意义.     

偏焦偏置抛物面天线的辐射特性

以馈源横向偏焦量Δy作为变化因素分析了偏焦偏置抛物面天线的远场辐射特性.在采用坐标转换、相位计算的基础上运用口径场法推导了远区电场的近似表达式,并对不同偏焦量Δy下的天线方向图进行了计算和比较分析.结果表明,随着偏焦量Δy的增大,天线主波瓣偏离抛物面的焦轴线角度越大,天线增益越小;而且主波瓣宽度越宽,旁瓣的不对称性越明显,第一旁瓣的相对强度也越大.     

计算对数周期偶极子天线相位中心的变步长法

为了提高计算对数周期偶极子天线(LPDA)视在相位中心的速度和精度,提出一种计算LPDA视在相位中心的变步长法,井计算LPDA的E面、H面视在相位中心,给出了E面、H面方向图半功率波瓣宽度内的最大相位差.最后,根据计算出的相位中心重新计算LPDA在E面、H面的相位方向图,在天线功率波瓣宽度内相位值平坦,表明该方法是有效的.     

FDTD-TDEEC混合法计算抛物面天线远区辐射场

应用时域有限差分一时域等效边缘电流(FDTD-TDEEC)混合法计算脉冲辐照情况下大口径抛物面天线的远区辐射场,先使用FDTD方法计算抛物面天线馈源的近场,再根据基尔霍夫面积分表达式(KSIR),求出表面上任意点的场对抛物面天线口径边缘上场的贡献,并将此贡献看作是入射脉冲,使用TD-EEC方法计算抛物面天线的远区辐射场.给出馈源为偶板子的算例,所得计算结果与EEC方法的结果符合较好.数值计算表明,抛物面口径边缘的绕射对抛物面方向图的副瓣有一定影响.该方法具有通用性,可有效分析其它类型馈源的各种电大尺寸的单反射面天线的远区辐射场,包括馈源偏焦的情况.     

MATLAB在反射面天线三维方向图中的应用

提出了一种反射面天线三维方向图的绘制方法。介绍了分析反射面天线辐射场的方法,并将表面电流法和口径场法进行了比较。给出了计算抛物面上的电流分布公式,论述了表面电流法的基本原理。运用MATLAB软件对反射面天线的辐射场进行了数值计算,阐述了程序主要语句格式和功能以及计算的流程图,得到了天线的二维和三维方向图,直观清楚地表现出辐射方向图的特点,为绘制反射面天线的方向图提供了一种方法。     

天线相位方向图分析

干涉仪测速定位系统对天线提出相位精度要求,主要是相位方向图的平坦性和天线对之间相位方向图的一致性。本文分析了影响抛物面天线远场相位特性的各种因素;根据微波天线相位中心讨论的现有成果,选取等效参考相心;利用口径场理论导出相位方向图的计算公式;同时考虑了天线转动中心偏离相位中心随指向变化引起的相移;并与实测的相位方向图进行比较,获得了较为满意的结果。     

基于不同等效面的漏波天线辐射特性研究

基于等效原理计算了一款分别使用线电流源与线磁流源激励的一维无限长漏波天线的总场辐射方向图和漏波辐射方向图.应用等效原理,两种辐射方向图均分别使用了等效面电流和等效面磁流两种不同的等效方法推导.使用谱域法推导出天线总场与漏波辐射场方向图的解析解并使用互易性原理推导出总场的辐射方向图以作对比.对比结果显示不同等效面得出的漏波场辐射方向图不同.     

雷达有源隐身技术研究

凡是能够减小目标信号特征使雷达探测能力降低的技术均属于雷达隐身技术。在有源隐身技术中，除了干扰方式处。有源对消是一处灵巧的信号消隐方式。主要讨论采样相干手段使目标散射场和人为引入的辐射场在雷达方向相干对消，对雷达接收机始终处于合成方向图的零点，从而抑制雷达对目标反射回波的接收这样一种有源对消隐身技术，计算了相干对消的波瓣特性、功率指标及对消波的幅相取值条件。     

Radiation characteristics of waveguide-excited dielectric spheres with matched sphere-air boundary

The results of experiments on the radiation characteristics of circular-waveguide-excited dielectric spheres with matched sphere-air boundaries are reported. The test data have shown that a waveguide-excited dielectric sphere, backed by a metallic hemisphere and with simulated quarter-wavelength matching at the dielectric?air boundary through surface perturbations, produces a directive pattern with a low side-lobe level, increased on-axis gain and reduced 3 dB beam-width, as compared with a simple wavegudie-excited dielectric sphere of the same diameter and an optimum horn with an aperture of identical cross-sectional area. Also, it presents a low voltage standing-wave ratio over the waveguide band.     

Numerical calculation of the radiation from a guiding structure of arbitrary cross-section

A quadrature scheme is described for the calculation of the radiation field of an open-ended guiding structure directly from the longitudinal field components of the mode in the aperture. The calculated radiation pattern for a rectangular waveguide and a regular polygon dielectric rod agree well with known results. Radiation patterns for rectangular dielectric rod are also presented.     

Calculation of Transient Radiation Parameters of Aperture

Transient radiated field from aperture antennas is derived by using the field equivalence principle. For Gaussian pulse excited uniform and tapered planar apertures, transient radiation parameters, such as radiation energy pattern, the half-energy beamwidth and directivity, are calculated. The simulation formulations for calculating the half-energy beamwidth and directivity are presented     

Radiation fields of the short-backfire antenna

A method for the approximate calculation of the radiation fields of a short-backfire antenna is presented. This technique is based upon the assumption that the aperture field is distributed approximately cosinusoidally in both horizontal and vertical planes as evidenced by near-zone field measurements. It appears that the short-backfire antenna is essentially a circular aperture antenna with cosinusoidal aperture field, and that the dipole functions merely as an exciter for this field.     

同轴波导口面的辐射特性研究

为了研究同轴口面的辐射特性,从同轴口面的电磁场的矢量模函数出发,应用口面场的傅里叶变换求解同轴口面的辐射场,研究了同轴区域的电尺寸、同轴喇叭张角与2个常用的高次模辐射特性之间的关系,给出了2个常用模式的比例与辐射方向图的关系和供工程设计用的参考数据。     

Optimization of the geometry of a TEM-horn for radiation of ultrashort pulses used as an element of an antenna array with controlled position of the main lobe

The finite-difference time-domain method is used to build the model of a TEM-horn with exponential longitudinal distribution of the characteristic impedance along the axis. This model is used to calculate the antenna energy pattern and the shape of the ultrashort pulse of the electromagnetic field in the far zone. Geometrical parameters of the antenna aperture are selected so as to increase the width and the uniformity of the energy pattern in the direction of radiation as well as minimize the level of the backward radiation.     

Analysis of Aperture Field of Circular Groove Guide Horn Antenna by Using FD-TD Method

This paper presents an instance of using FD-TD method to analyze the aperture field of circular groove guide horn antenna. This process is one part of a hybrid method to solve the radiation field of aperture antenna. To verify the calculated aperture field the radiation pattern is computed from it and compared with the measured one. Good agreement is reached.     

Time Domain Analysis of the Near-Field Radiation of Shaped Electrically Large Apertures

The near-field radiation of several electrically large apertures has been computed based on the aperture field convolution method, including a square aperture, a circular aperture, and a serrated edge aperture. The frequency range is 8.0–12.0 GHz. The aperture diameters are limited to 5.00 m and the corresponding electrical size is 133–200 wavelengths. The time domain spectrum has been obtained by chirp z-transform with a Hamming window and the mechanism for the generation of the aperture near-field radiation in time domain is analyzed. The calculation results demonstrate that the near-field radiation of the aperture can be approximately seen as the synthesis of a plane wave from the aperture, cylindrical waves from the edges, and spherical waves from the corners. By this method, the direction, position, and magnitude of incoming waves in the near-field region can be estimated, and the aperture design can be modified to meet the requirements of the near-field radiation. The near field of the three apertures mentioned above has been compared, and it is shown that the serrated edge aperture has more uniform direct wave and lower diffraction waves, making it a candidate for compact range (CR) aperture design.      

An analysis of millimeter wave quasi-optical gaussian beam radiation-perturbational expansion method

In this paper perturbational expansion of wave equation is used to analyse the Gaussian beam radiation efficiency and the near field distribution of aperture antenna. The analysis is also suitable at large angles from boresight because the Gaussian beam used here is corrected to satisfy wave equation. An approach of minimum deviation of aperture field is used to calculate the Gaussian beam radiation efficiency, and calculation results is compared with that of Wydle's[1].