The antennas on a mobile board and their electromagnetic compatibility

This paper presents the solutions of a problem of optimization in the decrease of antenna-coupling coefficients on a mobile board in case of limitations on coverage for each antenna. To determine a minimum value of an antenna-coupling coefficient for one pair of antennas, we use the Gauss-Zeidel optimization method or search method. When two or several antenna pairs have a common antenna, the coordinates of this antenna are determined by the compromise. The algorithms of optimum antenna placement are supported by the computer software and are tested for a case of four antennas.     

电磁环境对电子设备的影响分析

随着电子设备在军事、医疗卫生、航空航天、网络通信等多领域中的广泛应用,其重要性日益凸显,但因为其自身特性较容易受到电磁干扰,制约了其使用性能的有效发挥,为此,深入分析电磁环境下电子设备运行状态和受干扰程度,能够促进电子设备的不断完善,而本文正是以此为研究重点,分析了电磁干扰源及其对电子设备性能的具体影响,进而提出了预防和规避电磁干扰的措施.     

飞机进近着陆系统电磁环境建模与仿真

针对进近着陆系统电磁环境逐渐恶化的问题,提出将多种数值计算方法内嵌的模块化设计的电磁环境仿真方法,从模块化仿真模型的建立、模块间的接口及工作流程等方面对进近着陆系统电磁环境仿真做了系统阐述.并利用该方法在Matlab环境下对实际问题进行了仿真分析.研究表明,内嵌了多种数值计算方法的模块化仿真可以实现提前分析和预测复杂的电磁环境对着陆系统性能的影响,对机场的基本设施建设规划具有指导作用.     

复杂电磁环境分析研究

阐述了电磁环境的基本概念和意义,分析了电磁环境中的基本组成,着重对信息化战场电磁环境的复杂性作了进一步的分析和探讨,建立复杂程度衡量指标,最后应用层次分析法构建评价模型,为更好地完成复杂电磁环境下的信号构建奠定基础.     

FDTD analysis of electromagnetic wave radiation from systemscontaining horn antennas

The application of the finite-difference time-domain (FDTD) method to various radiating structures is considered. These structures include two- and three-dimensional waveguides, flared horns, a two-dimensional parabolic reflector, and a two-dimensional hyperthermia application. Numerical results for the horns, waveguides, and parabolic reflectors are compared with results from using the method of moments (MM). The results for the hyperthermia application are shown as extensions of the previously validated models. This new application of the FDTD method is shown to be useful when other numerical or analytic methods cannot be applied     

Simulation and analysis of antennas radiating in a complex environment

An accurate and efficient numerical solution is developed for predicting high-frequency radiation patterns of antennas mounted on curved surfaces. This solution employs the uniform geometrical theory of diffraction (UTD) and has mainly been used to analyze airborne antenna patterns. In this case the aircraft is modeled in its most basic form so that the solution is applicable to general-type aircraft. The fuselage is modeled as a perfectly conducting composite ellipsoid, whereas, the wings, stabilizers, nose, fuel tanks, and engines, etc. are simulated by perfectly conducting fiat plates. The composite-ellipsoid fuselage model is necessary to simulate successfully the wide variety of real world fuselage shapes. Since the antenna is mounted on the fuselage, it has a dominant effect on the resulting radiation pattern, so it must be simulated accurately, especially near the antenna. Various radiation patterns are calculated for military aircraft, private aircraft, and the space shuttle orbiter. The application of this solution to practical airborne antenna problems illustrates its versatility and design capability. The solution accuracy is verified by the comparisons between calculated and measured data.     

复杂电磁环境下的雷达对抗技术分析

从雷达面临的复杂电子对抗环境以及雷达抗干扰技术的特点出发,对几种典型的雷达对抗技术进行了分析,最后概述了雷达抗干扰的典型体制发展方向。     

Efficient electromagnetic analysis of line-fed aperture antennas in thick conducting screens

This paper presents a numerical and experimental verification of an approximate but efficient integral equation technique for the scattering by apertures in conducting planes with finite thicknesses. The approach is based on a perturbation method and modified Green's functions that take into account the finite metallization thickness. The computational effort and time needed for solving the problem are the same as in zero-thickness case. When compared to full-wave cavity treatment of thick apertures, the method is (depending on the number of unknowns) at least an order of magnitude faster. The method can be applied even to apertures of arbitrary shapes where computing the cavity's Green's functions is a difficult task. The results of simulations using the new approach show good agreement when compared to both results from full-wave cavity approach and measurements.     

基于复杂电磁辐射环境的电磁辐射检测方法研究与分析

随着信息技术的不断发展,多种电磁辐射源同时存在的电磁辐射环境日益复杂,各类场所的人为电磁能量显著增加。为了实现对复杂电磁辐射环境的分析,预防或减少电磁辐射的伤害,通过对单一辐射源检测方法开展研究,创新性地提出了复杂电磁辐射环境的概念及检测方法,包括相对中心检测法和相对轴线检测法,并结合单一辐射源检测结果,对现代城市环境中常见的复杂电磁辐射环境开展了检测,最后对电磁辐射情况进行总结并提出建议。     

UAT analysis ofE-plane near and far-field patterns of electromagnetic horn antennas

The uniform asymptotic theory (UAT) of diffraction has been applied to arrive at expressions valid for both the near as well as far-field patterns of antenna with edges, namely an electromagnetic horn. It is found that the theoretically computed results agree very well with experiment. The agreement is found to be better than that reported by earlier authors in the far sidelobe and backlobe regions. The same theory is valid for near field as well with the pertinent values of radial distance where the uniform theory of diffraction (UTD) requires a slope diffraction correction.     

The application of characteristic-mode techniques tovehicle-mounted NVIS antennas

Radio communications over relatively short distances, but beyond line-of-sight, present few problems nowadays, except in certain situations when no suitable, artificial means of relaying the signals exist. A mode of propagation, known as NVIS, or near vertical-incidence skywave, which relies only on the ionosphere, provides a solution. However, to exploit it requires careful choice of operating frequency, as well as the use of appropriate antennas. If the terminals are mobile, then the antennas, which are usually electrically small, can be the limiting factor. A method of optimizing antenna performance is presented that exploits the natural or characteristic modes of the structure on which the antenna is mounted. Extensive use is made of the method of moments, in the form of both the NEC and MININEC codes, to compute these modes, and to design and test antenna systems that exploit them. Measurements, made using an instrumentation package flown from a tethered balloon, compare very favorably with computed results     

基于统计分析的数据链电磁环境适应性研究

通过对无人机数据链在零均值和非零均值电磁干扰环境条件下的电磁兼容性概率函数的研究,检验系统在给定信号条件下的电磁兼容性概率,可以客观地反映出无人机数据链电磁环境适应能力的高低.从总体性能检测或环境适应性分析的角度考虑,利用具有可比性的传统误码率分析方法的验证及其取得的一致性结论,清晰地表明该统计方法的有效性.     

Beam-forming techniques operating on HF collocated antennas

Theoretical aspects and experimental results are presented for beam-forming techniques operating on an array of HF collocated antennas without the need for space diversity. This original application achieves the separation of two propagation modes associated with a given path on the ionospheric channel. A specific device, based on different types of active antennas, has been developed and experimental results validate this concept.     

基于结构误差的六边形相控阵天线电性能分析

相控阵天线(Phased Array Antenna,PAA)阵面加工、安装中产生的随机误差导致天线电性能的下降,严重制约高性能PAA的发展.通过考虑互耦参数,且将阵面存在的结构误差作为附加的相位因子引入到天线方向图函数中,建立了平面六边形PAA阵面结构误差与天线电性能之间的结构-电磁耦合模型,并仿真分析了考虑互耦时结构误差与天线电性能的定量关系,以及天线阵元个数变化时,阵元安装精度和阵面平面度对天线电性能的影响规律,为工程设计人员帝定天线结构方案与制造公差提供了重要参考.     

A novel technique for analysis of electromagnetic scattering frommicrostrip antennas of arbitrary shape

A new numerical procedure is developed for the solution of the electric field integral equation (EFIE) for arbitrary-shaped microstrip structures. This approach is superior over conventional EFIE techniques particularly in the low-frequency region or where the structure to be analyzed is electrically small. A pair of new basis functions is presented which are essential to the solution in the entire frequency range of interest. The new basis functions decompose the surface current density into divergenceless and curl-free parts which essentially get decoupled at the very low end of the frequency spectrum. Typical numerical results are presented for certain examples to illustrate the difference in the results between the two methods     

Optical simulation of microwave antennas

It has recently been suggested that microwave antennas may be simulated at optical frequencies using the neon-helium continuous gas laser. The present paper discusses various aspects of this problem and presents a simulation example using as a model the 96-element Australian array used to scan the surface of the sun at 80 megacycles. An optical system can be used for simulation in which an objective lens obtains the Fourier transform of the antenna aperture field which may be photographed. An additional lens produces an image of the antenna aperture field in the same air space as the far field pattern, thus permitting photographs of near field as well as far field patterns. Antenna masters are made as optical transparencies using photographic plates or film. Phasing may be obtained by using a variable thickness optical material evaporated on glass. Various combinations of array distribution, antenna weighting, and phasing are possible to simulate. Atmospheric perturbations are introduced on the antenna pattern by the use of two-dimensional phase delay patterns. Photographs are presented of the antenna aperture field, the far field pattern and several intermediate near field patterns.     

民航导航台电磁环境测试过程及分析

0 引言 民航导航台是以各种地面和机载导航设备向飞机提供方位、距离和位置信息,以保障飞机在昼夜间各种气象条件下的安全飞行;负责指挥飞机的起飞、降落以及飞行高度、飞行速度等重要参数.     

Primary-focus operation of shaped dual-reflector antennas

Primary-focus operation of reflectors designed for optimum performance in a shaped dual-reflector configuration is considered. Provided the reflector diameter is< 100 lambda, only a small loss in efficiency is suffered in comparison with a paraboloidal antenna.     

Efficient electromagnetic modeling of three-dimensional multilayermicrostrip antennas and circuits

An efficient method-of-moments (MoM) solution is presented for analysis of multilayer microstrip antennas and circuits. The required multilayer Green's functions are evaluated by the discrete complex image method (DCIM), with the guided-mode contribution extracted recursively using a multilevel contour integral in the complex _ρ-plane. An interpolation scheme is employed to further reduce the computer time for calculating the Green's functions in the three-dimensional (3-D) space. Higher order interpolatory basis functions defined on curvilinear triangular patches are used to provide necessary flexibility and accuracy for the discretization of arbitrary shapes and to offer a better convergence than lower order basis functions. The combination of the improved DCIM and the higher order basis functions results in an efficient and accurate MoM analysis for 3-D multilayer microstrip structures     

射电天文站电磁环境测量方法及分析

射电天文业务是接收来自遥远宇宙天体的射电信号进行研究的科学.由于来自宇宙天体的射电天文信号非常微弱,比通信系统的信号暗弱百万倍,使射电天文望远镜对周围电磁环境的要求极其严格.射电天文站址要选在电磁环境良好的地区,并在以后的运行中得到电磁环境的保护.建立一套测试射电天文站址电磁环境的设备和方法,对射电天文站址的电磁环境进行实际测试,并对实测数据进行科学合理地分析、评价,作为以后射电天文观测和保护电磁环境研究的依据都是非常重要的.