FAFFA加速的PO—MM研究复杂金属载体上线天线电磁特性

本文提出了一种快速远场近似(FAFFA)加速的混合物理光学-矩量法(PO-MM)，利用FAFFA加速计算矩阵方程中的矩阵矢量积，明显提高了计算效率．对物体表面上的远场组之间的耦合作用推导出了一组简洁的计算公式，并分析了计算复杂度．复杂金属组合体上线天线输入导纳、互导纳和方向性图的计算结果与文献结果一致．利用该方法分析计算了一个舰船模型上线天线的电磁特性．数值结果表明了这种方法的正确性和工程应用中的有效性．     

基模螺旋天线的研究

本文提出了一种计算基模螺旋天线的新方法.该方法采用螺旋线段对基模螺旋天线进行划分,只需少量分段就可用矩量法对其进行精确模拟分析.文中求出了螺旋天线上的电流分布和远场方向图,与直线段模拟计算结果吻合良好.求阻抗矩阵 Z时,利用螺旋天线的对称性和周期性,只需求出一小部分元素就可得到Z 矩阵的其它元素的值.该方法分段数少,使得计算时间和计算所需存储量大大减小,计算速度和精度显著提高.     

双圆柱体结构天线阵列的电流计算方法

在天线的设计过程中,天线表面的电流分布将对天线的性能产生重要影响。本文介绍了一种双圆柱体结构全向天线阵列的表面电流及等效端口导纳矩阵的计算方法,根据这个算法,本文计算了在一定物理尺寸下该天线阵列的电流分布和端口导纳矩阵。数值计算显示这种算法是可行的,结果是令人满意的。     

双圆柱体结构天线阵列的电流计算方法

在天线的设计过程中,天线表面的电流分布将对天线的性能产生重要影响。本文介绍了一种双圆柱体结构全向天线阵列的表面电流及等效端口导纳矩阵的计算方法,根据这个算法,本文计算了在一定物理尺寸下该天线阵列的电流分布和端口导纳矩阵。数值计算显示这种算法是可行的,结果是令人满意的。     

MLFMA分析复杂载体平台上天线问题

该文分析了导体介质复合结构平台上线天线的辐射问题。利用等效原理建立EFIE-PMCHW表面积分方程组,定义线、面和连接基函数描述复杂结构上电流分布,分析了导体介质分界面处基函数的处理;利用多层快速多极子方法(MLFMA)加速迭代求解过程中的矩阵矢量相乘运算,并用于有耗媒质求解。MLFMA的运用极大地提高了求解实际电大问题的能力。数值计算结果验证了方法的正确性和高效性。     

改进的IPO-CBFM 分析电大尺寸腔体的RCS

计算电大尺寸复杂腔体电磁散射时,迭代物理光学法与矩量法的混合方法（IPO-MM）是有效方法之一。为 了提高该算法的效率,在IPO 中使用快速远场近似（FAFFA）技术加速,在腔体复杂部分的MM 中使用特征基函数法 （CBFM）技术加速。在新的IPO/FAFFA-CBFM 混合法中,利用分块技术对求解矩阵进行降秩,使用传统的求解方法 即可求解方程,而不需要预条件处理与低频法的迭代求解方法。结果表明,新的混合方法有更高的计算效率和在单机 平台上解决更大复杂腔体电磁问题的能力。     

车载多天线系统的电磁兼容问题分析

本文采用矩量法和微波网络理论相结合的方法分析了车载多天线系统的电磁兼容问题，该方法先将天线系统等效为微波网络，然后采用矩量法求解该等效网络的导纳矩阵Y，利用该导纳矩阵可求得天线间的耦合度，文中也对发射功率较大的天线的近场分布进行了分析。     

波导平板裂缝天线阵的设计

利用商业软件HFSS的S参数仿真结果，采用等效网络法对矩形波导宽边纵缝进行互耦环境下的导纳计算；并利用天线远场幅度、相位方向图仿真结果，采用口径场反演方法，对阵中辐射缝参数进行修正。通过设计实例，验证了该方法非常适合于平板裂缝天线阵的设计，有效地提高了设计效率。     

变极化单脉冲环焦天线分析与实验

本文用物理光学法分析研究任意极化单脉冲环焦天线的近场分布和远场方向图.利用傅里叶级数展开公式,将四重积分分别简化为三重(近场)和二重积分(远场),大大简化了数值计算.实验结果证明了理论分析的正确性,数学模型和分析软件可用于大中型双赋形单脉冲环焦天线设计.     

球模式展开理论近远场变换及快速算法

基于球模式展开理论的近远场变换是天线球面近场测量系统实现的关键,它将待测天线在空间建立的场展开成球面波函数之和,由于其计算公式复杂,因而计算耗费时间长。该文在实际计算中利用快速傅里叶变换及矩阵的思想可以大幅度提高程序运行速度,节省计算时间。采用该方法对角锥喇叭天线的近远场数据进行仿真验证,结果表明外推远场的结果和理论值吻合良好,说明了该方法在保证计算精度的同时,可缩短计算时间。     

求解复杂载体天线辐射问题的近场预条件技术

提出了一种近场预条件技术与LDU分解法相结合的新技术,用于加速矩量法(MoM)分析复杂载体上线天线辐射问题中线性方程组的迭代求解.通过LDU分解可将系数矩阵中表示载体上单元相互作用的具有对角占优特性的子阵分离出来,构造一个矩阵分解形式的预条件阵.结合广义最小留数(GMRES)法,分别对装载在两个简单形体和一架大型飞机模型上的线天线的辐射问题进行了求解.数值结果表明,该方法可大大加快线性方程组迭代求解的收敛速度,提高分析计算效率.     

Modélisation d’une antenne-réseau et traitement optimal

An array antenna is modeled after a linear multipole filter, one part of which is connected to a distant source, radiating in a specified direction, while the relations between the other parts are characterized by the antenna admittance matrix. This modeling technique is applied to an array of parallel linear wire antennas. It is shown how the array admittance matrix can be evaluated numerically by a discrete quantization of the Maxwell’s equations with the proper boundary conditions (Harrington’s method of moments). The admittance matrix is then used to formulate the optimum signal processing for transmission (maximization of antenna gain, with or without constraints) and for reception (maximization of signalto-noise ratio). Along with the model of the array antenna that is submitted, a method of signal processing is developed in which accurate estimates are included of the losses that occur within the array elements as well as of the coupling between elements and of the noise arising in the receiving system. The antenna designer can thus optimize the geometric configuration of the array and study the phenomenon of superdirectivity with a more realistic approach than was hitherto possible.     

Measurement techniques for antennas in dissipative media

Methods used to simulate dissipative media environments for antennas are reported and special techniques developed to determine the electrical properties of antennas in such media are discussed. Tank systems for simulating infinite homogeneous isotropic media characterized by ratios ofalpha/betain the range0 < alpha/beta < 1.0are described along with the apparatus for determining the constitutive parameterssigmaandepsilonof the media. A new device for measuring antenna input admittance is presented which permits a simple measurement of admittance over a broad frequency range where conventional methods are cumbersome in field use. Apparatus for measuring antenna current and charge distributions is described together with a discussion of the associated probing errors. Measured admittances and current and charge distributions are compared with current theories for thin wire linear and loop antennas in the dissipative media and are found to be in good agreement.     

Modeling strategies of the input admittance of RC interconnects for VLSI CAD tools

In this paper, models of input admittance of RC interconnects are discussed in depth to understand and evaluate their loading effects on driving CMOS gates. From a detailed analysis of input admittance pole-zero location, arguments are derived to prove that their input admittance can be accurately approximated to that of a low-order equivalent RC circuit, in contrast to the case of timing analysis of RC wires. More specifically, 1st- or 2nd-order equivalent circuits are derived analytically via the moment matching approach, in contrast to previous analyses that rely on purely numerical approaches. Moreover, simple analytical rules to extend results to arbitrarily complex networks are derived, as opposed to the usual approach that requires numerical estimation of moments. Being fully analytical, the proposed approach permits one to develop models that are extremely simple (i.e. computationally efficient), as well as to gain an insight into the properties of input admittance of RC interconnects.The proposed equivalent circuits are evaluated and validated in situations that occur in real CAD design flows, where RC wire loading effects are estimated by CAD tools to perform the timing/power analysis of the buffer driving the wire. The analysis is validated through extensive simulations on a 65 nm CMOS technology. Well-defined criteria are also derived to select the appropriate model of RC wire input admittance for accurate timing/power estimations in VLSI CAD tools.     

Multimode Equivalent Networks for the Design and Analysis of Frequency Selective Surfaces

A modular technique originally proposed for waveguide junctions, the multimode equivalent network approach based on the integral equation formulation (IEMEN), is extended to the analysis of multilayer frequency selective surfaces integrated with waveguide array antennas. This technique represents each layer and transition between layers in terms of a generalized impedance or admittance matrix, obtained directly from the solution of an integral equation with reduced kernel. Thanks to the adopted formulation, the integral equation needs to be solved only in a limited set of frequency points. The IEMEN method is validated by comparison with results available in literature.     

Accurate model of arbitrary wire antennas in free space, above orinside ground

An accurate model of wire antennas in free space, above or inside lossy ground is presented in which the current is assumed to flow on the surface of the wire and the testing is also performed on the surface. To replace the traditional delta-gap source, a more accurate source model is developed by using the Huygens' principle. From this principle and reciprocity theorem, a variational formulation of the input admittance is derived. When the triangle function is chosen as both basis and weighting functions, all the elements of impedance matrix and source vector are formulated in closed forms, which can be rapidly computed. Several numerical results are given. Comparing with measured data, both the current distribution and input impedance by this model are more accurate than those of delta-gap model     

X 波段加膜片式单脊波导裂缝天线的研究

等效导纳值是波导宽边纵缝天线的关键设计参数。为克服传统波导裂缝天线副瓣偏高、设计效率低下等问题,本文提出了一种单脊波导裂缝天线的改进设计方法,在传统波导裂缝阵列天线设计的基础上,利用等效导纳值对天线等效电路的影响,在裂缝单元下增加金属膜片,通过改变金属膜片的高度,优化裂缝等效导纳值,使得每个裂缝口径场分布更加接近于理论设计值,并在设计过程中使用牛顿迭代法提取导纳进一步缩短设计时间。通过设计实例表明:应用此方法设计单脊波导裂缝天线能够有效抑制副瓣电平,天线方位面副瓣电平可达到-30 dB 以下;在满足主要指标要求的前提下,设计效率显著提升。     

A novel ray tracing on general paraboloids of revolution for UTDapplications

Analytical expressions have been obtained for the ray-geometry parameters on the general paraboloid of revolution (GPOR) using a novel technique known as the geodesic constant method. These ray parameters are in a one-parameter form and can be readily employed in high-frequency EM antenna scattering problems. As an example, the uniform theory of diffraction (UTD) mutual admittance results are presented for two antennas located on the GPOR arbitrarily, in three dimensions     

Mutual coupling in aperture-coupled patches on cylindrical reflectors calculated using a spectrum of two-dimensional solutions

The mutual coupling between groundplane slots in aperture-coupled patch antennas on cylindrical structures is calculated using a moment method in the Fourier domain. By separating the three-dimensional (3D) problem into a spectrum of two-dimensional (2D) problems an efficient calculation of the admittance is possible. To increase the accuracy in the mutual admittance calculation, an asymptotic extraction technique is used. Several cases of antenna geometry are investigated and comparison is made to measurements. The method used allows for efficient and accurate analysis of dual polarized aperture-coupled patches placed on general cylindrical structures, as in the case of base-station antenna arrays for mobile communications.     

Analysis of zigzag antennas

The integral equation technique is used to find rigorous solutions of the current distributions on zigzag antennas. Through a new decomposition technique the currents are analytically separated into forward and reflected components, from which accuratek - betadiagrams of the structures can be obtained. For the case of log-periodic antennas, the forward component of the current also gives the characteristic admittance of the antenna, which can be determined hitherto only through many measurements or calculations.