Computer Programs for the Calculation of the Horizontal Far Field Radiation Pattern and Directivity of Full Wave Dipole Panel Antennas

Two computer programs have been developped for the calculation of the horizontal far field radiation pattern and the directivity of full wave dipole panel antenna arrays for the VHF TV Broadcasting. The programs are written in Basic and were run with the aid of a HP-86 personal computer.     

Analysis of reflector antenna systems with arbitrary feed arraysusing primary field superposition

In contrast to secondary pattern superposition, where the fields reflected from the main reflector arising from each element are superimposed in the far field of the reflector, the approach presented here sums the primary fields at the reflector surface before the physical optics radiation integral is performed. The method allows each feed array element to have arbitrary position, orientation, pattern, and excitation (magnitude and phase). In addition, it is inherently efficient because evaluation of only one time-consuming radiation integral is required, rather than one per feed element as in secondary superposition. The method allows for accurate calculation of the power radiated from the feed, permitting the reflector gain and spillover efficiency to be determined within the context of a single computer program. The accuracies and characteristics of this method are demonstrated with several examples     

Probe correction of spherical near-field measurements

Probe correction has been implemented in a computer program which calculates antenna far fields from spherical nearfield measurements. The computer program has been applied to near-field measurements on a satellite model, and the accuracy of the computed far field is significantly improved, compared with the results obtained without probe correction.     

高压半导体器件电场的二维数值分析

利用作者们开发的有限元二维分析程序对高压半导体器件的电场分布进行了模拟分析.给出了这类器件中有离子注入、场板和栅极延伸等终端结构时的电场分布;根据模拟结果得出突变平面结表面电场的近似公式,将此公式与圆柱坐标对称解和计算机模拟结果进行了比较.     

Diffraction by an arbitrary subreflector: GTD solution

The high-frequency asymptotic solution of diffraction by a conducting subreflector is studied. By using Keller's geometrical theory of diffraction and the newly developed uniform asymptotic theory of diffraction, the scattered field is determined up to an including terms of orderk^{-1/2}relative to the incident field. The key feature of the present work is that the surface of the subreflector is completely arbitrary. In fact, it is only necessary to specify the surface at a set of discrete points over a random net. Our computer program will fit those points by cubic spline functions and calculate the necessary geometrical parameters of the subreflector. In a companion paper by Y. Rahmat-Samii, R. Mittra, and V. Galindo-Israel, the scattered field from the submflector is used to calculate the secondary pattern of an arbitrarily shaped reflector by a series expansion method. Thus, in these two papers, it is hoped that we have developed a "universal" computer program that can analyze most dual-reflector antennas currently conceivable. It should also be added that our method of calculation is extremely numerically efficient. In many cases, it is one order of magnitude faster than the conventional integration method based on physical optics.     

并行算法性能简析

随着计算机实际应用范围的扩展，针对在不同领域中应用计算的问题本身存在的并行性和单机性能的限制，基于提高计算机在实际应用计算中的计算速度为目的，通过对PI计算程序的研究，结合近年来的教学实践，并通过对并行计算加速比和效率两个并行程序性能评价参数的分析，提出了应用并行计算程序是提高计算机计算速度的有效途径的结论。该结论将对复杂的多个进程计算问题提供有效地解决方案。     

Calculation of the radiation pattern, gain and input impedance of a Yagi antenna

A computer program is presented for the calculation of the radiation pattern, gain and input impedance of a Yagi antenna having up to ten elements.     

Efficient computation of the far field of parabolic reflectors by pseudo-sampling algorithm

The newly developed pseudo-sampling representation is applied for computing the far field of an offset parabolic reflector with a cluster feed illumination. A new comb-type fast Fourier transform (FFT) algorithm is used in a computer program. Both precision and computational time are analyzed, demonstrating the excellent performance of the method.     

平面近远场变换的快速算法

基于考虑探头补偿的平面近远场变换理论 ,根据实际需要 ,提出了一种工程实用的平面近远场变换快速算法。通过该算法由近场测量数据变换得到的天线远场方向图 ,既能达到任意分辨率 ,又能节约计算内存和提高计算速度。     

有源相控阵天线发射方向图测试简易方法

有源相控阵天线需要对接收和发射两种状态的天线方向图进行测试。现有天线测试远场只能进行接收态的方向图测试,介绍了在远场进行发射态方向图测试的一种简易方法。利用远场的测试转台和发射喇叭,使用频谱分析仪接收有源相控阵天线发射的数据,编制测试软件采集处理数据,即能实现有源相控阵天线发射方向图的测试。该测试方法简单易行。     

Scattering of a Plane Wave on a Ferrite Cylinder at Normal Incidence

The scattered field is given as a series of cylinder functions. If the ferrite cylinder is magnetized along its axis the scattering pattern becomes asymmetrical about the direction of incidence. Approximation formulas for the thin cylinder and the far field zone are given. It is shown that in the first approximation the amplitude is an even function and the phase angle of the field is an odd function of the scattering angle. Exact numerical results have been obtained with a Univac digital computer. By a suitable arrangement of the ferrite cylinders, a unidirectional pattern can be obtained which is controlled by the applied magnetic dc field.     

基于VPN的水箱远程实验系统的设计与实现

设计了一套基于VPN的水箱远程实验系统，通过资源共享来提高实验装置的利用率，描述了该系统的硬件平台、下位机运行程序和上位机监控界面。采用VPN技术，使实验者不必亲临现场，只需通过互联网即可接入系统，编写下载和调试程序，解决了目前基于工业控制系统的远程实验系统只能”监”而不能”控”的问题。     

MOS型新型功率器件终端场分析与实验

采用二维有限元数值分析的方法，开发了用于反向偏置ｐ－ｎ结分析的模拟软件，可以模拟与ＭＯＳ型功率器件反向耐压有关的终端浅结场环、场板、ＳｉＯ２介质及界面态。为高压器件的终端研究、设计和优化提供了精确而有效的ＣＡＤ工具。此文介绍模拟所采用的物理模型和模拟方法，并以三环浅结带场板终端为例，给出部分模拟实例、结论及实验结果。     

带反射腔开式套筒天线方向图计算

采用电磁场数值域中的矩量法对带反射腔开式套筒天线进行分析，并通过计算机编制程序计算出了该天线的方向图以及半功率波瓣宽度，结果与有单位提供的实测基本吻合。     

Ultrawide-band modeling of transient radiation from aperture antennas

A new method for the numerical calculation of transient field radiated through aperture-type antennas (slot, open-ended waveguide, and horn) is described. The finite-difference time-domain method is applied for the near-field prediction in the close surrounding of the antenna and a proper data-fitting procedure of the aperture field, involving interpolating functions with separation of space- and time dependence, permits: 1) to calculate "off-line" the radiated field without the need to store a great amount of data; 2) to avoid, in the case of far field, the numerical evaluation of radiation integral; and 3) to obtain approximate far field formulas which are still separable with regard to space and time. The method enables a full data reusability in calculation of field pattern over a wide angular range at a same time, or of the transient response at fixed observation points.     

Novel FDTD simulation method using multiple-analysis-space for electromagnetic far field

Wide-band undesired electromagnetic noise near electronic systems, which includes small noise source like the printed circuit board (PCB), is a current problem in the field of electromagnetic interference. However, the estimation method for the electromagnetic noise near a system under test has not been established. This paper proposes a newly developed estimation method of the electromagnetic noise for a wide area, from near to far field, using the finite difference time-domain (FDTD) method. The proposed FDTD simulation method is an estimation technique for near to far field with multiple analysis spaces (MAS). The MAS has an internal analysis space (IAS) and an external analysis space (EAS). The analysis near a radiation source can be calculated in the IAS. The EAS is the outside space from IAS, which is for calculation of the far field. It is expected that the proposed FDTD method by MAS (FDTD-MAS) decrease in the calculation cost in terms of computational time and memory costs, especially for estimation of radiation from PCB. The principle procedure of the FDTD-MAS method is described in the first part of this paper. As example of advantages of the calculation and confirmation of the calculation accuracy, the electric field distributions radiated from a 1-GHz half-wavelength dipole antenna in an IAS of 0.3/spl times/0.3 m/sup 2/ area and an EAS of 7/spl times/7 m/sup 2/ area are used as examples. When the cell size ratio of IAS to EAS is changed from 6 to 20, the FDTD and theoretical values show good agreement. It is indicated that the FDTD-MAS simulation method is one of the most powerful tools for the estimation of electromagnetic noise from near field to far field from small and thin source.     

Comparison of measured and calculated antenna sidelobe couplingloss in the near field using approximate far-field data

Computer programs presently exist to calculate the coupling loss between two antennas provided that the amplitude and phase of the far field are available. It is shown that when this far-field information is not available it is possible to specify approximate far fields from a knowledge of the sidelobe of each antenna along the axis of separation and the electrical size of each antenna. The ENVLP computer program developed by M.H. Francis and A.D. Yaghjian (ibid. vol.AP-34, p.952-5, July 1986) was modified for this purpose. Measurements of near-field coupling loss between two moderately sized microwave antennas were made to determine the effectiveness of using approximate sidelobe level data instead of the detailed far fields. Comparison of the measured and computed coupling indicates that the use of approximate far fields gives an estimate of the coupling loss with an uncertainty of about ±5 dB     

Near-field blockage of an ultralow sidelobe antenna

An analytical model is presented which describes the farfield radiation pattern of an array antenna blocked by a vertical or horizontal metallic cylinder in the near field of the aperture. The implementation of this model as a generalized computer program has been completed, and the computed radiation patterns have been verified by extensive measurements on a low sidelobeX-band slotted waveguide array. The effects of the blockage are summarized graphically for a wide range of obstacle sizes and distances, and for aperture illuminations ranging from conventional reflector-type distributions to ultralow sidelobe distributions. Using dielectric or absorptive coatings to improve the radiation pattern in the presence of cylindrical obstacles is proposed as a logical extension to the existing model.     

The complex propagation constant of multilayer waveguides: analgorithm for a personal computer

An algorithm for the calculation of the propagation constant of integrated-optics waveguides is developed. The waveguide may consist of any number of layers with complex refractive indexes due to gain and loss. It allows the additional determination of the field distribution. Thus, all parameters necessary for heterostructure laser development can be calculated. The resulting program was run on a personal computer; numerical results are presented