基于OFDM技术和自组网技术的海上频谱感知传输系统研究

控制电磁频谱权成为控制信息权的核心,战场频谱管理是夺取控制电磁频谱权的重要保障.电磁频谱监测与管理系统中需要进行频谱信息的传输,而数据传输系统就是实现这个功能的关键.由于海上气象条件复杂,网络信号稳定性不佳,舰载电磁监测设备远离海岸而且机动性强.针对这一点,提出了一种基于OFDM技术与移动自组网技术的海上频谱感知传输系统,完成监测信息的远程实时传输.     

EM simulators=CAE tools

The emergence of vastly refined algorithms for finite-element analysis, which are putting electromagnetic simulators into the hands of any engineer who can afford a personal computer, is discussed. Field simulation allows an engineer to analyze the electromagnetic behavior of a device without building a physical prototype and taking measurements. The way in which simulation technology is changing the design process is illustrated by considering the design of a coax-to-waveguide transition. The field simulation model developed by the design engineer is passed to the manufacturing engineer, who runs parameter studies of the device by varying key dimensions and materials to determine the sensitivity of device performance to these parameters. Further, the field simulation model helps determine the impact of unforeseen changes during manufacturing due to variations in supplies and facilities. The process used by the finite-element simulators to solve Maxwell's equations is described. Two typical CAE applications are examined: a microwave low-pass filter design and a study of electromagnetic coupling in digital circuit interconnections. Pointers for selecting electromagnetic CAE software are given     

Electromagnetic and thermal analysis for lipid bilayer membranesexposed to RF fields

Experiments with pulsed radio frequency fields have shown influence on the low-frequency behavior of lipid bilayer membranes. In this paper, we present an electromagnetic and thermal analysis of the used exposure device to clarify whether the observed effects have a thermal cause and to determine the fields at the lipid bilayer. In order to model the very thin lipid bilayer (about 5 nm) accurately, the electromagnetic analysis is broken into several steps employing the finite difference time domain technique and a finite element/boundary element hybrid approach. Based on the obtained power loss due to the electromagnetic fields, the temperature change is calculated using the finite element method for the solution of the heat conduction equation. Both, the electromagnetic and the thermal analysis are performed for a variety of material parameters of the exposure device. The electromagnetic analysis shows that the exposure device is capable of producing voltages on the order of 1 mV across the lipid bilayer. The combined electromagnetic and thermal calculations reveal that the temperature oscillations due to the pulsed radio frequency fields are too small to directly influence the low-frequency behavior of the lipid bilayer.     

场路结合法分析设备电磁辐照效应

电子设备机壳内部往往会内置多层印制电路板,外界电磁干扰很可能通过设备的外接导线进入设备内部进而对电路板造成损坏。针对这种情况,采用全波分析法获得受干扰设备的相关参数,利用该参数建立等效源模型;等效电路法分析内部电路板上电路的电磁特性。通过全波分析法和等效电路法相结合的方式来分析外界电磁干扰进入设备内部时所造成的影响,为处于高频电磁干扰环境中的电路工作特性研究提供新思路和参考。     

电磁环境复杂度等级评估模型

综合考虑靶场复杂电磁环境适应性试验的特点和实际需求,研究了电磁环境复杂度等级分类和评估方法。首先分析了电子装备类型及电磁环境适应性特点。其次提出基于电子装备类型的电磁环境复杂度等级评定方法,即对于雷达类和通信类设备基于信噪比、侦察类设备基于信号脉冲流分别制定复杂电磁环境等级。第三考虑用频装备天线扫描,给出了电磁环境复杂度等级动态统计分析表达式。该研究可为电磁环境适应性试验和作战指挥研究提供重要支撑。     

光控伺服系统建立、建模与仿真

介绍了一种具有抗电磁干扰,信息传输快的光控伺服系统的组成,并详细阐述了此系统关键组成部分——光伺服阀中光驱动器所应用的光致伸缩陶瓷材料(PLZT)的应用原理以及其在阀中具体的实用结构。对光控伺服系统的各个环节进行系统级的建模与仿真分析,讨论其抗电磁干扰能力,比较不同控制方式PLZT光执行机构精度的影响。探讨了光控伺服系统,尤其是光伺服阀光驱动器的实用性以及其有待解决的问题。     

某加固网络交换机电磁辐射超标的分析与改进

加固网络交换机为某兵种地面车载设备,在对其进行电磁兼容试验时,电磁辐射测试项(RE102)出现超标。经对设备的分析、发现机箱孔缝、电缆屏蔽、电源防护及接地方式等方面存在导致电磁泄漏的不利因素。采取减小孔缝、加强电缆屏蔽、改进电源外罩与接地方式等措施后,设备顺利通过RE102测试项。     

Passive electro-optic antenna using polymer material

The experimental results of a polymer microwave electro-optic antenna are reported. The device amplitude-modulates an optical input beam with a free-space propagating electromagnetic wave. By using a new dipole printed antenna, the electromagnetic energy is concentrated inside the device. An antenna factor of 168 dB/m is achieved with only 1 mum of electro-optic polymer     

GaAs器件电磁脉冲效应实验与毁伤机理研究

介绍了GaAs低噪声器件电磁脉冲效应实验响应的易损敏感端,对所确定的敏感端注入电磁脉冲方渡,研究了器件在静态时的损伤阈值.根据GaAs器件易损性薄弱环节,从GaAs器件的结构、内部缺陷等出发,探索电磁脉冲对GaAs器件易损性薄弱环节的损毁机理.通过对毁伤实验分析,进一步阐述了电磁脉冲对器件存在潜在不稳定性失效,对器件和整机系统设计者和使用者具有一定的参考意义.GaAs微波低噪声器件在EMP正脉冲注入情况下,获得的损伤阈值约为3.024μJ.在EMP负脉冲注入情况下,损伤阈值约为10.02μJ.初步认为GaAs FET的正脉冲EMP比负脉冲EMP更易损伤.     

基于电磁超材料的微波单向传输圆波导设计

微波隔离器是微波系统中不可或缺的器件,常见的隔离器都采用了铁氧体旋磁材料配合吸收负载实现电磁波的单向传输.这种器件虽然可以使电磁波单向传输,但是并不能改善能量的浪费问题,还增加了系统的复杂度.针对上述问题,本文基于电磁超材料设计了一种微波单向传输的圆波导,使用波导内壁涂覆折射率逐渐变化的材料来影响电磁波的传输特性,从而...     

Reliability study of AlGaN/GaN HEMT under electromagnetic,RF and DC stress

In the context of studying the reliability of RF High Power Amplifiers (HPA) in their real environment, a study of the behavior of AlGaN/GaN HEMTs performances under electromagnetic stress is presented in this paper. The DUT has undergone several stress combinations (electromagnetic stress, electromagnetic and RF stress, electromagnetic and DC stress, …). The near field setup is used to disturb with electromagnetic field the device under test (DUT). Degradations in DC and power characteristics are observed for all stress types. This could be associated with electron trapping within the AlGaN barrier and AlGaN surface leading depletion of the 2-DEG.     

DC-6 GHz宽带同轴电磁辐照实验装置的设计研究

由于传统TEM小室的频带宽度不能满足日益增长的宽频带需求,该文采用同轴结构设计了一个DC-6 GHz的宽带电磁辐照装置。该装置基于传输线理论和阻抗匹配原理,采用锥形过渡与圆同轴连接的结构,在端口处选用N型连接器,与腔体的连接实现了良好的阻抗匹配。利用CST仿真软件进行建模优化,最后对仿真结构进行加工与调试,仿真结果表明,该同轴电磁辐照装置在DC-6 GHz频率范围内S11均在–10 dB以下,由于加工的误差测试结果在个别频点稍有偏差,但趋势和仿真结果具有较好的一致性,吻合较好,证明该辐照装置具有良好的传输性能。该文设计的同轴腔在电磁辐照系统中具有很好的应用价值。

     

Electromagnetic wave effects on microwave transistors using afull-wave time-domain model

A detailed full-wave time-domain simulation model for the analysis of electromagnetic effects on the behavior of the submicrometer-gate field-effect transistor (FET's) is presented. The full wave simulation model couples a three-dimensional (3-D) time-domain solution of Maxwell's equations to the active device model. The active device model is based on the moments of the Boltzmann's transport equation obtained by integration over the momentum space. The coupling between the two models is established by using fields obtained from the solution of Maxwell's equations in the active device model to calculate the current densities inside the device. These current densities are used to update the electric and magnetic fields. Numerical results are generated using the coupled model to investigate the effects of electron-wave interaction on the behavior of microwave FET's. The results show that the voltage gain increases along the device width. While the amplitude of the input-voltage wave decays along the device width, due to the electromagnetic energy loss to the conducting electrons, the amplitude of the output-voltage wave increases as more and more energy is transferred from the electrons to the propagating wave along the device width. The simulation confirms that there is an optimum device width for highest voltage gain for a given device structure. Fourier analysis is performed on the device output characteristics to obtain the gain-frequency and phase-frequency dependencies. The analysis shows a nonlinear energy build-up and wave dispersion at higher frequencies     

Lead—Lead telluride Schottky-barrier microstrip

Observations of some interesting properties of the II-VI semiconductor PbTe result in the realization of a Pb-PbTe Schottky-barrier microstrip having a slowing factor as large as 450 for propagating electromagnetic waves. The properties of PbTe are briefly described, and the key features that produce a large slowing factor are explained. The theory of device operation at cryogenic temperatures is presented, along with details of device fabrication and actual device performance.     

碳纳米器件光电特性的电磁散射分析

用经典的宏观电磁理论对由碳纳米材料制成的光敏器件的光电特性──主要为功率吸收特性[1],作了适当的建模分析.在该模型中,将光处理为频率较高的电磁波,纳米材料处理为有损介质材料,应用经典的电磁散射理论中的并矢格林函数建立了相应的散射模型,由此求得器件中碳纳米管束处的电场强度,并分析其吸收功率特性,从而对该光敏器件的设计给出一些指导性的意见.最后用商业全波仿真软件HFSS对该结果进行了验证.     

雷电电磁脉冲模拟研究

根据雷电在远场产生的电磁辐射场具有平面波的性质 ,提出了一种由冲击波发生器和平行板横电磁室 (PPTC)组成的简易远场雷电电磁脉冲 (LEMP)模拟装置 ,实现对远场雷电电磁脉冲辐射场的模拟 ,并依照 IEC标准用试验验证了该装置的可行性。在此基础上 ,利用此装置对典型电火工品 (EED)进行了辐射试验。     

Vibration control of flexible rotors using a passive magnetic device working on the principle of electromagnetic shunt damping

Excessive rotor vibration can propagate the micro-cracks and hence the premature failure of the rotor system. A passive magnetic device working on the principle of electromagnetic shunt damping (EMSD) is proposed to passively control the rotor vibrations. Although, these EMSD-based damping systems are quite common in the literature, however, there is not even a single article available in the literature, showing the application of such a device passively controlling the rotor vibrations from a distance. Due to the flow of flux between the rotor, stator, and air gap, the modeling procedure for such an EMSD-based system changes completely and is not available in the literature. Due to rotor movement, there is a variation in the magnetic flux provided by the permanent magnets placed in the device. Due to electromagnetic interactions, electric currents are induced in the windings provided in the device. When these currents are allowed to pass through electrical resistance, damping forces are generated. In this way, vibration energy is converted into heat energy. In this research, it is observed that the damping effect is maximum for an optimal value of electrical resistance. The effect of several turns in the windings and permanent magnet thickness is also investigated in terms of the production of damping forces. The efficiency of the device is mathematically proved through simulations. Further, experimental results verify the effectiveness of the proposed device.     

某非金属壳体控制设备的电磁屏蔽设计方法与研究

为了解决某非金属壳体控制设备电磁屏蔽效能低,抗外部电磁干扰能力差及对外辐射超标的问题,本文结合工程可行性提出了某非金属壳体控制设备电磁屏蔽改进措施;通过对某非金属壳体控制设备的壳体、开关以及缝隙屏蔽设计,提高该设备电磁屏蔽特性。试验测试证明,改进后控制设备满足GJB 151B-2003中RE102及RS103项目的要求。     

磁共振射频信号对医疗器械影响的数值和实验研究

广泛研究了在MRI系统中的医疗器械射频致热问题。采用全波电磁仿真和热仿真工具,研究了器械长度与器械尖端周围的最大温升的相关性。测试结果显示,“最坏情况”的温升测量结果与仿真数据一致。该工作提出了一种高效、准确的方法,用来评估多种不同尺寸的医疗器械在磁共振环境下的射频致热情况。     

S-domain methods for simultaneous time and frequencycharacterization of electromagnetic devices

An efficient procedure is developed for simultaneously characterizing the time-domain and frequency-domain behavior of electromagnetic devices. The procedure works in the complex-frequency plane called the s-domain-and provides an analytical expression for the behavior of the device at any frequency and for any transient excitation. This analytical expression is obtained by first evaluating a reduced-order model of the poles and zeros of the device. These poles and zeros are then used to characterize the device in terms of rational polynomials in the s-domain. Two different methods for evaluating reduced-order models are presented. One is called asymptotic waveform evaluation (AWE) and is combined with the finite-element method; the other is called adaptive Lanzcos-Pade sweep (ALPS) and is combined with the boundary-element method. The resulting reduced-order models provide the frequency-domain behavior of the device over a broad bandwidth. Using the Laplace transform, these reduced-order models also provide the time-domain behavior. Several numerical examples have been run using commercial electronic design automation (EDA) software to demonstrate that this solution procedure is a highly efficient and accurate way to characterize the electromagnetic performance of real-life devices