圆周扫描地基SAR地形表面提取辅助的三维成像算法

圆周扫描地基合成孔径雷达(GBCSAR)具备大视场、高分辨率等优势,且具备三维分辨能力,在复杂场景形变监测领域具有重要意义.但在大场景下目标点数量庞大,常规的三维成像方法耗时很长,难以满足实时连续监测的需求.因此本文提出一种针对GBCSAR的地形表面成像方法.在场景形变监测时,地形表面形变往往可以反映场景形变趋势,针对...     

Analysis and modeling of a high-temperature superconducting floating resonant strip in waveguide

A two-gap floating resonant strip is used for characterization of the high-temperature superconductor, YBa₂Cu₃O_7?δ. The method has the advantages of simplicity, no electrical contact, operation at various resonant frequencies, and of requiring only a small sample. An analysis was devised that allows for the accurate design of the strip dimensions to produce a desired resonant frequency. Experimental measurements in X and Kuband (8–18 GHz) agree well with the calculations. The sensitivities of the circuit to positional errors and size variations of the resonant strip were investigated. The surface resistance was measured and compared favorably with the theory.     

An Analysis of Gap in Microstrip Transmission Lines

Although microstrip transmission lines have been widely used in microwave integrated circuits, the discontinuity structures in the microstrip transmission lines such as a gap, an abruptly ended strip conductor, and so on, have hardly been analyzed. An analytical method and numerical results for a gap capacitance in the microstrip transmission line are described. The equivalent circuit parameters are formulated with three-dimensional Green's functions, based on a variational principle. The numerical results are in good agreement with the published experimental data. The fringing effect of an abruptly ended strip conductor is also investigated.     

Transient Analysis of a Directional Coupler Using a Coupled Mlcrostrip Slot Line in Three-Dimensional Space (Short Paper)

In recent MIC techniques, double-sided MIC has been studied because its advantages in propagation characteristics are greater than that conventional MIC's. A coupled microstrip slotline is one of them. Its application to various circuit elements has often been discussed. But the coupled microstrip slotline is essentially three-dimensional structure, so the analysis demands a rigorous three-dimensional treatment. Also, the recent high-speed pulse technique demands analysis in the time domain. The present paper treats a directional coupler using the coupled microstrip slotline in three-dimensional space and time. The results of the directional coupler analysis is presented with the complicated time variation of the three-dimensional electromagnetic field. So, the mechanism of the directional coupling phenomena that is produced by the propagation characteristics of the even and odd modes is presented in the time domain, In particular, the instantaneous diagram of the Poynting vector details the energy flow in the transient process. For the analysis of the characteristics of the complex microwave device, these results present the utilities of the various field distributions that are obtained by the three-dimensional vector analysis in the time domain.     

激光相变硬化可视化分析

提出激光加工热响应的空间温度场可视化方法并对相变硬化进行分析,应用映射原理,建立空间温度场数据点着色色彩与温度的对应关系,用相视化方法分析了光束功率密度和移动速度对空间温度分布及相变硬化带的影响。方法可以直观、形象地显示温度场分布状态,预测相变硬化的深度和宽度,为研究激光束与材料相互作用时的参数优化提供了理论基础。     

Rigorous full-wave space-domain solution for dispersive microstriplines

The eigenmode problem for the open microstrip line is analyzed in the space domain starting from the calculation of a dyadic Green's function in the spectral domain. The transverse and the longitudinal current are discretized using the method of moments. A point-matching technique is used to impose the boundary condition, i.e., zero tangential electric field, on the strip. The edge conditions at the end points of the strip are explicitly incorporated and special care is taken to accurately retain the static behavior of the field on and near the strip. Special attention is given to the variation of the current distribution as a function of frequency     

Transient Analysis of a Stripline Having a Corner in Three-Dimensional Space

The transient analysis of electromagnetic fields has shown its utility not only in clarifying the variation of the fields in time but also in gaining information on mechanisms by which the distributions of an electromagnetic field at the stationary state are bronght about. We have recently proposed a new numerical method for the transient analysis in three-dimensioual space by formulating the equivalent circuit based on Maxwell's equation by Bergeron's method. The resultant nodal equatiou is uniquely formulated in the equivalent circuit for both the electric field and the magnetic field. In this paper, we deal with the stripline which should be analyzed essentially in three-dimensionaf space because of its structure, The time variation of the electric and magnetic field of the stripline having a comer is analyzed and the remarkable changing of distribution of the field is presented as a parameter of time and of conditions imposed by the corner stucture.     

Accurate Analysis of Coupled Strip-Finline Structure for Phase Constant, Characteristic Impedance, Dielectric and Conductor Losses

Propagation constant, characteristic impedance, dielectric loss, and conductor loss of coupled strip-unilateral finline is here computed for the first time. The technique of analysis is based on the assumption of hybrid wave propagation implemented through the spectral domain approach for the phase constant. A perturbation method together with the spectral analysis has been applied to find the losses. The basis functions used to approximate fields within unilateral finline gap and currents on the strip have been selected as Legendre polynomials for the unbounded field or current and trigonometric functions for bounded field or current. The Green's function matrix in the spectral domain for the two distinct planes of the coupled strip-unilateral finline has also been presented. This gives the opportunity for direct implementation in the analysis of other similar structures. The possibility of the extension of the technique to shielded stratified dielectric with distributed planar conductor within different layers has been also discussed.     

Modal analysis of strip-loaded diffused optical waveguides by a variational method

The propagating modes supported by strip-loaded three-dimensional diffused optical waveguides are analyzed in detail theoretically by using a variational method. Some typical numerical examples of the propagation constants and the field distributions are illustrated. The dependence of propagation characteristics on the geometrical parameters of the loading dielectric strip is discussed.     

Transient Analysis of the Electromagnetic Field for a Wave Absorber in Three-Dimensional Space

In recent years, large-scale structures such as tall buildings, large bridges, and towers cause severe reflection and diffraction in the propagation of electromagnetic waves. The most effective means for improvement of these characteristics is coating an electromagnetic wave absorber on the surfaces of structures. At the present time, determination of the performance of a coating and the estimation of its effects are carried out on a practical basis. Beforehand, however, theoretical clarification of absorbing characteristics is necessary for better design of a structure. This analysis demands the unified treatment involving both characteristics of absorber materials and the shapes in three-dimensional space of structures to which they are applied. Also, the analysis of propagation characteristics of a pulse wave in the time domain will be important. In this paper, we report the fundamental treatment of absorbing characteristics, including boundary conditions of the structure. The method of time-domain analysis in three-dimensional space and time is used. This method is formulated by Bergeron's method and based upon the equivalent circuit of both Maxwell's equation and characteristics of the medium. As an example, the performance of a very thin coating of absorber with magnetic loss is presented. The variations of field distribution for changes of magnetic-loss term including permeability and the frequency of incident wave, are shown. The absorbing characteristics for a pulse wave in the time domain are also given as a parameter of incidence angle.     

基于虚拟现实技术的激光传感器数据多维可视化方法

传统的基于WebVR的激光传感器数据多维可视化方法,基于几何模型的激光传感器数据多维可视化方法与基于三维GIS空间的激光传感器数据多维可视化方法均存在数据处理速度慢的问题,为此设计一种基于虚拟现实技术的激光传感器数据多维可视化方法。采集激光传感器数据,对数据预处理,利用八叉树方法对数据空间进行划分,并定义传递函数,目的是为了获得三维数据场的数据属性,建立三维对象渲染模型,根据虚拟现实技术中的点、线、面等构建模型,以此完成激光传感器数据多维可视化处理。实验对比结果表明此次设计的基于虚拟现实技术的激光传感器数据多维可视化方法比传统的三种方法处理速度快,能够快速地传递激光传感器数据信息。     

三维极化幅度调制解调器

从空间电磁场的数学描述出发,给出了对无线通信信号幅度、极化辐角与极化相位角进行三维联合调制解调的方法。根据描述空间电磁场各参数之间关系的方程,首先建立了三维联合调制信号的模型,然后讨论了三维联合调制信号通过矢量天线发射的实现方式,并给出了在接收端通过信号幅度检测及其波达方向(DOA)极化参数估计这2个步骤来实现对三维联合调制信号进行解调的策略;分析了三维联合调制误码率的计算方法及其性能。分析与仿真结果均表明:所提出的调制解调方法具有传输速率高和误码率低的优点。     

Scattering by thin dielectric strips

A plane wave incident on a thin dielectric strip with infinite length is considered, letting the incident electric field vector be parallel with the edges of the strip. The field is expanded in the dielectric region as the sum of three plane waves (the forced wave and two surface waves). Thex-axis andy-axis propagation constants are known for each wave, and Galerkin's method is employed to determine the amplitudes of these waves. Finally, the far-zone scattered field is determined by considering the polarization currents radiating in free space. Numerical data are presented to illustrate the scattering properties of lossless and lossy dielectric strips as a function of the angle of incidence and the width of the strip. The calculations show excellent agreement with an earlier moment method using pulse bases and point matching.     

电磁场积分方程时间步进解法稳定性的研究

本文对用三角片状单元剖分及做相应的矢量基函数展开,采用空间域的Galerkin矩量法,时间域采用步进递推方法解电磁场时空积分方程并进行了程序实现.研究了这种方法的优缺点,分析了计算中出现的振荡发散现象,与细线栅网结构剖分方法进行了比较,从中得到关于时空积分方程时间步进解法稳定性的一些结论.     

Three-dimensional analysis of a cylindrical waveguide converter forcircular polarization by the spatial network method

Two types of converters for generating a circularly polarized wave from a linearly polarized one are analyzed using the spatial network method (SNM). The converter types studied are: those loaded with metal plates in a cylindrical waveguide and those loaded with a fin. The cutoff wavelengths are computed from the frequency response by applying the fast Fourier transform. The phase-shift constants and guide wavelengths are computed from the spatial and time variations of the electric field distribution. The whole distribution of fields obtained by the SNM is shown to provide detailed information on the field properties, such as the local field concentration. In particular, the process of generating either a circularly or elliptically polarized wave from a linearly polarized wave is shown by three-dimensional and time-domain analysis. It is confirmed that the fundamental characteristics of the converters agree well with the analysis and measured results     

Diffraction of high-frequency electromagnetic waves by curvedstrips

The authors describe the construction of a high-frequency solution in the geometrical theory of diffraction (GTD) format for the generation of edge-diffracted space rays and edge-excited surface waves by an electromagnetic wave normally incident on the edge of a curved impedance strip. The transformation coefficients necessary for the analysis of the diffraction on curved surfaces with equal vanishing face impedances are tabulated in a form appropriate for numerical applications. The procedure for evaluating the diffracted field excited by the edge of a cylindrically curved strip, which can be associated with a reflector antenna or an aperture on a curved surface, is presented for both perfectly and nonperfectly conducting cases     

Quadratic relationships for a strip small-period array

A strip array with a period small with respect to the wavelength is considered. The far field of this array is described by the nonlocal equivalent boundary conditions. It is shown with the help of the active power theorem that a near field transferring the active power along metal strips exists in the strip. The relationships connecting the far field on the strip surface with the active power of the near field are derived. It is demonstrated with the help of the Lorentz lemma that the near field has a nonzero quadratic shape and the relationships connecting it with the far field are obtained. A method of determination of the far field components on the array surface that are normal to the array plane is proposed. This method allows one to take into account the finite values of the quadratic forms.     

Application of extended boundary conditions and the Haar wavelets in the analysis of wave scattering by thin screens

A recent approach to solution of 2D scattering problems for electromagnetic waves scattered by thin screens is analyzed. With the use of examples of scattering by a strip and an unclosed cylindrical surface, it is shown that the proposed approach has no advantages in terms of the efficiency of numerical solution over a well-known approach based on exact integral equations for currents that have singular kernels and that are solved with the Krylov-Bogoliubov method.     

大跨度天基数据链的TDD时隙调度分析与优化

针对天基数据链系统卫星间的传播时延较大且节点间距离变化较大等特点，提出了一种提高时频资源利用率、提升系统容量、减小时延的方法。在时分多址与空分多址相结合的接入方式下，进行了时隙调度的分析与优化，利用卫星星座的空间复用与大跨度传播时延特性，采用时隙编排、收发状态调整、帧格式优化等手段，将信道利用率和系统容量提升了1倍，将卫星节点在某一方向获得服务的平均等待时间缩短为原来的1/4，提高了天基数据链系统的服务质量。