电磁环境仿真中电波传播模型研究及仿真分析

研究了移动通信信道的电波传播损耗模型,通过对不同模型的仿真对比,指出在飞行器控制通信仿真中宜采用Longley-Rice模型的点对点模式,以适应飞行器控制通信的特殊需求。抽取航天飞机雷达地形测绘使命(SRTM)高程数据作为传播模型点对点模式中传播路径的详细地形剖面数据,仿真结果显示电波预测值与理论值吻合度较高。     

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.     

圆锥对数螺旋天线辐射特性的理论分析

采用有限元-边界积分方程方法(FE-BI)系统分析了不同结构参量变化对双臂圆锥对数螺旋(CLS)天线性能的影响。分析了不同工作频率对圆锥螺旋天线方向图的影响,改变螺旋线包角对其性能进行了讨论;研究了圆锥半张角对辐射特性的影响。研究表明:螺旋线包角和圆锥半张角对有限长CLS天线的辐射方向性有较大影响,实际应用中应充分考虑。     

典型雷达电磁环境效应特征数据模拟系统

针对雷达系统复杂电磁环境效应,在分析雷达面临复杂电磁环境的基础上,研究电磁环境要素表征方法,提出雷达信号处理和数据处理阶段电磁环境效应量化指标,建立雷达电磁环境要素信号模型、雷达信号接收与处理、雷达数据处理模型,给出雷达电磁环境效应数据模拟方法,支持不同复杂电磁环境要素的参数化输入,并动态仿真复杂电磁环境与雷达系统的作用过程,输出各个节点的效应表征参数瞬态和统计值。初步结果验证了研究思路的正确性,能够为建立复杂电磁环境要素与复杂电磁环境效应之间的映射关系提供大样本数据支撑。     

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.     

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     

基于LiDAR点云的地理电磁环境建模及仿真研究

在复杂地理环境中,不规则的地形和多样化的地表覆盖物会给电波的传播造成较大的影响.针对数字高程模型（Digital Elevation Model,DEM）电磁建模缺少地表覆盖物信息的不足,研究了基于LiDAR点云的地理电磁环境的建模.采用数学形态学方法对格网化后的LiDAR点云数据进行处理,从点云数据中先后提取了地物、地形的信息,在此基础上,对各种地物赋予其相匹配的电磁参数,得到了更为准确的地理电磁环境的模型,并采用抛物方程模型对有真实地表覆盖物环境下的电波传播特性进行了仿真分析.相较于传统的基于DEM的电磁建模,该电磁建模方法能够获取到地形、地物的信息,更全面地考虑到地物对电波传播特性的影响,预测结果也将更加准确有效.     

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.     

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.     

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.     

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.     

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。     

基于电磁环境数据的信息挖掘与关联分析

城市通信技术的改革换代和用频设备的逐渐增多使得电磁环境变得越来越复杂。充分了解频谱资源利用的特性是提高频谱管理效率的关键。为了更全面地探索频谱利用的特点,提出一套完整的对复杂多样电磁环境大数据进行详细数据质量分析和处理的流程,分别对处于同一服务的不同信道、处于不同服务的不同信道进行频谱相关性分析,证明了频谱之间的相关性;对电磁环境大数据进行属性构造,构造了频率维占用度和时间维占用度属性。引入图像处理领域的多维混合高斯模型,对电磁信号进行背景噪声的去除,提取电磁信号,为后续的信息挖掘和关联分析奠定基础。     

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     

无人机通信干扰电磁环境半实物仿真系统

针对战场环境下复杂传播环境及敌方干扰对无人机通信系统性能的影响,提出了综合信道衰落和干扰共同作用下的无人机通信信道理论模型。在此基础上,基于微波暗室设计实现了无人机通信干扰电磁环境半实物仿真系统。该系统利用硬件现场可编程门阵列(Field Programmable Gate Array,FPGA)实时模拟无人机通信信道和干扰信号,利用微波暗室模拟外场的无线传播环境,并通过天线位置和角度调节装置模拟发射机、干扰机和接收机之间的空间位置特性。实测结果表明,该半实物仿真系统能够真实复现无人机通信干扰电磁环境,可用于无人机数据链抗干扰性能的测试和评估。     

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.     

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.