半电波暗室中的EMI辐射骚扰试验测量不确定度分析与评定

半电波暗室能模拟理想的开阔场情况,符合电磁波在自由空间中的传播规律,在此特定环境中测量EMC一个重要技术指标——辐射骚扰场强,简单介绍测量不确定度理论,详细分析辐射骚扰场强的测量不确定度来源与评定,并给出评定结果,为实验室的电磁兼容检测提供指导。     

New Method for Computer Identification Through Electromagnetic Radiation

The electromagnetic waves emitted from devices can be a source of information leakage and can cause electromagnetic compatibility (EMC) problems. Electromagnetic radiation signals from computer displays can be a security risk if they are intercepted and reconstructed. In addition, the leaks may reveal the hardware information of the computer, which is more important for some attackers, protectors and security inspection workers. In this paper, we propose a statistical distribution based algorithm (SD algorithm) to extracted eigenvalues from electromagnetic radiate video signals, and then classified computers by using classifier based on Bayesian and SVM. We can identify computers automatically and accurately through electromagnetic radiation by using the algorithm in our experiment environment.     

电动汽车电磁兼容技术及其发展趋势(英文)

The electromagnetic compatibility of electric vehicles is not only the important technology issue in researches,development and industrialization of electric vehicles,but also the key research area of ...     

The DES raligun facility at CEM-UT

The Center for Electromechanics at The University of Texas at Austin (CEM-UT) has constructed a facility for the operation of electromagnetic (EM) launcher experiments. The facility was specifically designed to investigate distributed-energy-store (DES) railguns. Experiments conducted in the facility have demonstrated the DES railgun concept using a 1-m long, four-stage DES railgun. Investigations have begun on a 4-m, ten-stage DES railgun to demonstrate operation of such a system at higher projectile velocities. The capabilities and design of the major components of the facility are described. Also presented is a review of the experimental development of the railgun system. The DES railgun facility is a versatile laboratory test bed facility for EM acceleration experiments.     

之江实验室声学实验室设计和性能测试

之江实验室声学实验室包括消声室、半消声室、混响室和听音室,结合实验楼整体布局,确定了声学实验室内部结构尺寸,提出了声学设计性能要求,为类似声学实验室的设计和规划提供参考。建成后,按照JJF 1147、JJF 1143和GB/T6881.1-2002分别对消声室、半消声室、混响室和听音室声学性能进行了测试,结果表明,该声学实验室达到了预期设计目标,可提供高精度的声学环境,为之江实验室开展相应的声学研究提供了基础环境条件支撑。     

Hypervelocity impact testing using an electromagnetic railgun launcher

An electromagnetic (EM) railgun launcher facility has been developed to routinely conduct hypervelocity impact tests. Two types of completely reusable EM launchers have launched sabot/impactor packages between 2 and 43 grams to velocities between 1.5 and 8.5 km/s. The highly reliable railguns have conducted over 250 projectile launchings and have established a projectile/launcer data base covering interior as well as exterior ballistic considerations. A conventional type instrumented ballistics range is compatible with the EM launcher and can be used to conduct anti-armor and lethality experiments at hypervelocities.     

A VME-based quench detection and logging system for superconductingmagnets

Quench detection is one of the crucial parts in the superconducting magnet test facility, specially related to the safety issue of the measurement environment. Consequently, those old systems, mainly relying on analog/TTL gate technologies, tend to be carefully adopted with minimum modification even for a new measurement facility, to maintain the working functionality. For a new measurement environment, readjustment of the system is necessary to control the different noise environment, and to incorporate the new measurement system configuration. For this purpose, an understanding of the physics of the quench-induced signals and noises is recommended to customize a new system. We have recently developed a prototype of the new fully digital quench detection system for the Magnet Test Lab. (MTL), Superconducting Super Collider (SSC) Laboratory, based on five out-of-shelf VME cards supported by a real-time O/S VxWorks. The new digital system not only provides improved signal processing and additional logging functions, but also supports user-friendly interfacing of parameter control and status display. One demonstration shows the modularity, simplicity, versatility, and compatibility of the new with the existing systems. This paper describes the overall system design, with the development and test environment     

频分多址法用于硐室盲炮检测与识别的试验

为探明硐室爆破中的盲炮,在高精度磁法、瞬变电磁法和瞬态电磁耦合法的研究基础上研究开发了频分多址法。该法是利用电磁波在大地中的传播规律,在不同装药硐室中预置发射不同频率的电磁信号发生器,在地面安装无线检测接收系统,通过接收到的不同频率信号来实现硐室盲炮检测与识别。试验结果表明,电场信号信噪比低、反应微弱,磁场信号的信噪比高,采用频率在1000Hz左右的磁场信号作为检测的信号源的实用性更好;频分多址法可以检测与识别出地下225m的盲炮,能满足地下硐室盲炮检测的距离要求;检测精度可达到2Hz,能同时有效地检测与识别地下单个及多个盲炮的存在。     

Hearing aids' electromagnetic immunity to environmental RF fields

In this work, the electromagnetic interference on hearing aids was evaluated. Electromagnetic (EM) immunity tests on different types of hearing aids were carried out, using signals of intensity and modulation comparable to those present in the environment. The purpose of this work is to characterise the interference, establishing the immunity threshold for different frequencies and finding out which types of hearing aids are more susceptible, and in which frequency range. The tests were carried out in a GTEM cell on seven hearing aids, using AM and GSM signals in the radiofrequency (RF) range.     

Near-Field Electromagnetic Characterization and Perturbation of Logic Circuits

We propose here a nondestructive electromagnetic (EM) near-field test bench for both EM compatibility and susceptibility of circuits. This setup permits both the collection of the near field and injection without contact of a disturbing EM field, all through a probe. Exhaustive characterizations of probes are undertaken via simulations and experiments. According to their design, they are supposedly linked more to the electric or the magnetic field. Simulations of their EM behavior are undergone to fix their optimal geometries, leading to the best measurement performances. It is shown by both the simulations and the S-parameter measurements that their presence does not interfere with the electric behavior of the device under test. Then, logic circuits are characterized from the EM point of view, with the help of this test bench. Circuits are placed on three different printed boards: one double-sided low-frequency board without a ground plane and two single-sided boards with a ground plane and a design that is more or less optimized. EM near-field mappings highlight the strong field areas of the circuits. The need for a ground plane is highlighted. Field patterns on the traces are linked with those observed on microstrip lines. Then, an EM aggression is injected over a supposed sensitive zone of the circuit. Whichever printed board is considered, a parasitic signal superimposes itself on the output signal of the gates. Deepened studies are undergone to exhaustively explain the phenomena observed.     

Performance of the first Japanese large-scale facility for radon inhalation experiments with small animals

A radon test facility for small animals was developed in order to increase the statistical validity of differences of the biological response in various radon environments. This paper illustrates the performances of that facility, the first large-scale facility of its kind in Japan. The facility has a capability to conduct approximately 150 mouse-scale tests at the same time. The apparatus for exposing small animals to radon has six animal chamber groups with five independent cages each. Different radon concentrations in each animal chamber group are available. Because the first target of this study is to examine the in vivo behaviour of radon and its effects, the major functions to control radon and to eliminate thoron were examined experimentally. Additionally, radon progeny concentrations and their particle size distributions in the cages were also examined experimentally to be considered in future projects.     

ZM4300光学遥感器空间环境模拟试验设备新技术

ZM4300光学遥感器空间环境模拟试验设备为了满足对温度、真空度、污染量、振动及多种试验模式的要求,采用了一些新技术措施,包括:多种试验模式、污染综合控制技术、大尺寸热沉精确控温和高温度均匀性、热沉兼具液氮制冷和乙醇制冷(机械制冷)模式、多种液氮流程运行模式、卸载隔振设置等。     

混响的混合高斯概率密度建模

混合高斯模型能够有效地拟合混响背景的一维概率密度分布。常用的混合高斯概率密度模型参数估计方法是EM迭代算法,但这种算法的主要缺点是估计精度过分依赖于初始值。而GreedyEM算法通过往混合模型中不断地加入高斯分量,能很好地解决这一问题。文章将多维图象处理中的GreedyEM算法加以合理简化,并给出模型自动定阶方法,从而成功应用于水声混响的一维混合高斯模型建模中。实验结果表明:应用新算法能从混响接收数据中准确拟合其概率密度曲线,并且能适应不同的数据长度,具有很好的通用性。     

基于SEA分析验证的混响箱-消声室实验方法设计及隔声性能研究

不同于以往的理论、经验设计,采用低频段的声固耦合法、中高频段的统计能量法(SEA)对设计的混响声场进行声学分析,提高混响水平。根据虚拟结果建立混响箱实物,置于半消声室内进行测试,混响箱结构本体的噪声衰减量超过50 dB,混响时间达到混响要求,混响场内不同位置声压值差距均小于2 dB,该混响箱设计满足混响声场的要求;将SEA法隔声计算结果与应用混响箱-消声室法对板件的隔声测试结果进行对比,两者吻合良好;因此该实验方法能实现很好的隔声效果。通过该方法可快速对单层板及夹层板件进行隔声测试,发现吻合频率效应对隔声性能影响较大;以上研究对工程应用有较大的参考意义。     

基于PXI的水下目标辐射噪声和信号模拟器

文中以宽带和多目标信号为模型,在虚拟仪器开发环境LabWindows/CVI下,设计和开发了基于PXI总线的水下目标模拟器。目标模拟器产生24阵元平面水声基阵的接收信号,在实验室里模拟海洋环境下的目标回波、混响和环境噪声,提供测试水声设备所需的各种目标信号。最后给出了该系统在水声自导系统调试和性能测试应用中的结果。     

The Design of an Automated, High-Accuracy Antenna Test Facility

This paper presents the step-by-step application of proven far-field range and instrumentation design techniques to a specific antenna measurement problem, describes the resulting facility design, and presents the predicted measurement uncertainty. Fundamental electromagnetic design criteria for an outdoor, far-field facility establish minimum dimensional requirements for the range design and limiting values of source-antenna directivity. Electromagnetic compatibility of the facility is assured by frequency coordination with existing and planned services in the area surrounding the available site. Additional design constraints for this facility included restricted measurement time, reduction of spurious test enclosure effects, limited available terrain, and required data quality. In this case, the required range length is in excess of 6500 ft, and paraboloidal source antenna diameters up to 23 ft are required. The frequency coordination problem was solved by exploiting the natural terrain features and configuring the measurement system as "test-on-transmit." Signal and reference paths share the same range cable. The quantity of data that must be handled in the available measurement interval required the use of a computer-based measurement system.     

Plasma diagnostics and heating in fusion programs and the possible role of free electron lasers

In the research on controlled thermonuclear fusion there is a wide utilization of electromagnetic (EM) sources with regard to both plasma diagnostics and plasma heating. In this paper the analysis is focused on the applications to magnetic fusion lines, principally on tokamaks. Concerning the diagnostics, scattering of EM waves, which has the widest and most various applications of EM sources, is reviewed. The physical principles of Thomson and resonance fluorescence scattering are illustrated and the requirements of EM sources are outlined. Finally the most urgent needs are reported indicating possible and useful developments of FELs. Heating is then discussed and the three principal frequency ranges are indicated. The present and future principal projects of magnetic fusion are reported together with their EM power requirements and wave frequencies for plasma heating. It is suggested that a possible application of FELs is in the field of electron cyclotron heating.     

Hybrid predistortion to compensate third- and fifth-order intermodulation of a 2 GHz power amplifier using cuber predistortion and second harmonics injection

A new circuit construction technique that actively utilises second harmonics injection (HI) to realise fifth-order predistortion (PD) for power amplifiers (PAs) with memoryless AM/AM and AM/PM conversions is proposed. Applying a combination of the proposed technique and cuber predistortion (CPD) to third-order distortion yields the simultaneous compensation of both third- and fifth-order intermodulation distortion (IM3 and IM5); capabilities are not possible with the conventional third-order PD approach. Since the proposed method can be implemented as a simple analogue circuit, it betters compactness and lowers cost. In order to derive the PA bias condition at which second HI works most effectively, a complex power series nonlinear model that allows both amplitude and phase nonlinearities to be dealt with simultaneously is used. To confirm the author's compensation theory, a 2 GHz band PA and a hybrid lineariser that employs second HI and CPD are fabricated and experiments are performed. About a 20 dB simultaneous reduction in IM3 and IM5 is achieved with the two-tone test. A W-CDMA one-carrier test is also conducted to verify the improvement in adjacent channel leakage power ratio compared with CPD only.     

预白化与小波变换联合的混响抑制方法研究

针对主动声呐在强混响背景下匹配滤波器检测性能不理想的问题,提出了将预白化与小波变换联合处理方法。首先将混响预白化处理,然后通过小波变换将混响和回波信号分解到不同的尺度空间下,在尺度空间进行阈值量化处理,对有用的信号成分进行数据重构,最后利用重构的数据进行匹配滤波处理,使得混响被有效抑制,改善检测性能。仿真和试验数据处理结果验证了该方法的有效性,信混比可以提高约3 dB。