Introduction to the special issue on high-power electromagnetics (HPEM) and intentional electromagnetic interference (IEMI)

A new threat to civil society has recently emerged. It is known as intentional electromagnetic interference (IEMI) and covers the threat of intense electromagnetic disturbances that may be applied to the sophisticated electronic systems that are so important to our daily lives. This paper provides a brief background for the threat, defines important terms, describes the different types of electromagnetic threats, explores the importance of topological concepts, summarizes the current understanding of equipment susceptibility, provides an overview of protection concepts, and summarizes the ongoing work in international standardization. This paper also serves as the introduction to the IEMI papers in this special issue.     

Dependence of the criterial levels of damage in semiconductor structures under the action of high-power electromagnetic pulse on the pulse rise rate

It is demonstrated that the criterial (critical) levels of thermal damage of the semiconductor structures with p-n junctions depend on both electromagnetic pulse energy and power and the pulse rise rate. The temperature of destruction of the junction that is found from the solution to the heat-conduction equation is chosen as the critical damage level. At a constant pulse power, the energy needed for the damage decreases with increasing pulse rise rate.     

基于脉冲耦合的超宽带高功率电脉冲源

以固态半导体器件为基础,基于超快电子学中的晶体管雪崩导通理论,利用脉冲耦合原理,在时域上将多路高压皮秒脉冲耦合输出,获得了超宽带高功率脉冲。通过四路脉冲耦合实验验证了该设计思路的可行性,提高了输出脉冲功率。实验中,单路高压皮秒脉冲的幅度为1.33kV,宽度为770ps,峰值抖动≤1%,脉宽抖动≤1%,四路脉冲耦合后,输出脉冲幅度为2.66 kV,宽度为875 ps,峰值抖动≤1%,脉宽抖动≤1%。该方法可以推广至多路脉冲耦合,获得更高的功率。     

高功率激光器上的SBS脉冲压缩

:对高功率激光器上SBS脉冲压缩技术的研究工作进行了详细的回顾 ,比较了几种常用的SBS脉冲压缩系统 ,总结了常用于脉冲压缩的几种物质的布里渊参数 ,并分析了SBS脉冲压缩技术的可能的发展趋势。     

A high-power long pulse excimer laser

Excimer lasers operating at high average powers are becoming important for materials-processing applications. A long-pulse excimer laser with automatic spark preionization which provides a pulse energy of 1 J with an optical pulse length of 200 ns full-width half-maximum for XeCl is described. Successful scaling of the repetition rate to 220 p.p.s. is discussed along with requirements for gas flow.<>     

A compact radiator of high-power electromagnetic pulses

The design and parameters of a compact radiator of high-power electromagnetic nanosecond pulses designed for simulation of ultra-wideband exposures in electromagnetic compatibility problems are described. It is shown that the effective pulse power of the radiator is 3 GW in the forward traveling wave and 15 GW in the wave reflected from the reflector. The effective density of the continuous energy spectrum is 17 mJ/MHz at 0.3 GHz.     

Transmission of electromagnetic pulse into the head

Characterstic of electromagnetic pulse transmission in homogeneous spherical models of human and animal heads are studied as a function of time and position. The incident pulse waveform is described by a triple exponential waveform which exhibits close agreement with measured pulse shapes. The transmitted pulse is shown to be proportional to the time rate of change of the incident pulse, with peak occuring at the leading surface of the spheres.     

高功率啁啾高斯脉冲在光纤中传输的形变研究

从光纤广义非线性薛定谔方程出发,定义了用于衡量脉冲形变大小的脉冲形变因子,定量地分析了在传输过程中脉冲形变因子、临界长度、临界功率及初始啁啾之间的关系。结果表明:在传输过程中,当入射脉冲的峰值功率一定时,正啁啾脉冲的形变比负啁啾脉冲和无啁啾脉冲的形变小;当脉冲的初始啁啾一定时,脉冲传输的临界长度随着传输功率的增加而降低,且随着功率的增大,不同初始啁啾脉冲的临界长度趋于一致;在传输距离一定时,临界功率与初始啁啾呈线性变化,且啁啾的漂移对正啁啾脉冲的临界功率影响较大。     

On the electromagnetic pulse produced by nuclear explosions

The electromagnetic pulse (EMP) produced by the gamma rays from nuclear explosions is discussed. The gamma rays produce a current of Compton recoil electrons, and these electrons produce further ionization so that the air becomes conducting. The Compton current leads to the generation of electromagnetic fields according to Maxwell's equations. The conductivity tends to limit the magnitude of the fields. Approximate methods of solving the equations are described by considering time regimes in which various terms in the equations are negligible, e.g., either the conduction current or the displacement current can be dropped. Further advantage is obtained by replacing the transverse fields by outgoing and ingoing waves; outgoing waves are dominant at early times. Features of the solutions are described for nuclear bursts at the ground surface and at high altitude. The history of EMP is reviewed briefly.     

Double-ended thyratrons in high-power burst mode pulse modulator applications

The use of four-gap double-ended thyratrons in a 30- to 100-µs pulse modulator is described. The PFN-type modulator operates at 105-kV peak, charged from the 11-kV public supply, and powers an ill-matched and potentially unreliable load directly at 30 to 70 kV without a pulse transformer. The maximum repetition rate is 200 pps. The completed modulator has been delivered to the customer and successfully recommissioned. Satisfactory operation is reported with 200-MW 6-kJ pulses in bursts of average power up to 400 kW; this is well in excess of the published ratings of the tubes employed. The methods used to obtain this performance are discussed and the main details are given of pulse discharge, energy dump, and switched charge circuits appropriate to the thyratrons used. The possibility of uprating the modulator is mentioned, and certain recent developments in large thyratrons are discussed. These include a new pentode-type electrode system which should give improved performance with simpler deck circuitry. For extended bursts at long pulse lengths the realistic maximum capability of single tubes in current production seems to be about 1-GW peak at 2-MW average power.     

核电磁脉冲地波传播规律

介绍了核电磁脉冲地波传播的理论计算方法,研究了当大地电导率大于0.005 S/m时,地波传播函数随频率及传播距离的变化规律,并计算了不同传播距离核爆电磁脉冲的地波电场。结果表明,频率越高,传播距离越远,传播函数的幅值越小;核爆电磁脉冲的传播距离为500 km时,电场的幅度会有大于一个量级的衰减。     

Propagation effects for electromagnetic pulse transmission

We review past research on the propagation of electromagnetic pulse signals over the surface of the earth with emphasis on analytical methods to predict waveforms. The best example is the electromagnetic field radiated from a lightning stroke that can be observed at global distances or very close in if one has sufficient motivation. In any case, the propagation channel will distort the signal wave shape because of the strong frequency dependence of the attenuation factors and the phase velocities of the modes. We begin with a flat earth model that has the virtue of simplicity particularly when displacement currents in the earth are relatively small compared with the conduction currents. Here we see that the rise time of the ideally radiated step function signal is of the order of a few microseconds at a range of 50 km over average land paths. Such a prediction is in accord with published experimental data. At greater ranges, earth curvature comes into play and we show here how various analytical and numerical methods can be used in overlapping time regions which serves as a good consistency check. Other complicated effects such as mixed land-sea paths and ionospheric influences are also reviewed.     

From electromagnetics to system performance: a new method for theerror-rate prediction of atmospheric communications links

An original and general method is proposed to predict the impact of electromagnetic effects due to the environment on the error performance of microwave communications systems. The method is based on the concept of a process-oriented model which consists of a simplified representation of the physical phenomenon responsible for transmission impairments and simulates its influence on the signals received by any given communications link. The method yields a thorough characterization of the system impairments in both the time domain, by calculating the fluctuations of the received signal during the evolution of the physical process, and the frequency domain, by inferring the communication channel transfer function from the frequency dependence of the received waveform. In addition, by introducing the simulated channel transfer function as a filter in a communications system simulation software, the method evaluates the degradation induced in the system performance. Three applications as different as scintillation due to turbulence in clouds, depolarization by rain and ice crystals, and interference in the presence of diffraction on obstacles demonstrate the ability of the method to deal with actual radio-communications system impairments     

Design of high-power ultrashort pulse amplifiers by expansion and recompression

A system that expands and recompresses an ultrashort pulse by means of diffraction gratings is described. The expansion can be large enough to broaden the pulse to several nanoseconds. In this manner, as the signal and pump pulses have similar lengths, high-efficiency amplifiers can be designed. The expansion avoids inefficient energy storage in high-gain amplifiers and nonlinear effects in the amplifier medium, and the amplified spontaneous emission is drastically reduced by working in a saturated amplifier regime.     

Dynamic characteristics of double-clad fiber amplifiers for high-power pulse amplification

Based on numerical modeling, the dynamic characteristics of high-power ytterbium-doped double-clad fiber amplifiers during the amplification of nanosecond pulses with kilohertz repetition rates are comprehensively analyzed. The temporal pulse energy, power, upper-level population distribution, amplified spontaneous emission, stored energy, pulse waveform evolution, etc., are emphasized in this paper. Some practical issues in amplification processes, such as the impacts of reflected pulses from the external surfaces and the fluctuation of input pulse energy on the amplifier performance, are also discussed. The models and results are important for the design and development of high-power double-clad fiber amplifiers.     

脉冲雷达发射机的电磁兼容设计

从电讯设计、结构工艺设计等方面分析了脉冲雷达发射机的电磁兼容性设计思路与方法。     

铜蒸气激光器中高压大功率脉冲变压器的研制

为了实现铜蒸气激光器电源的小型化,采用高压大功率脉冲变压器对储能电容进行开关脉冲充电的电路拓扑,通过建立设计和输出模型,采用铁基超微晶材料,研制了高压大功率脉冲变压器,在14kHz下实现了13kV的充电电压,传输功率超过2．3kW。通过控制IGBT的触发脉宽,可实现输出电压和功率的调节。     

大功率半导体激光器的高精度脉冲电源设计

为了满足大功率半导体激光器脉冲应用的实际需求, 针对单脉冲内电流平顶下降问题和重复性情况下电流稳定性降低的问题, 设计了一种多参数宽范围可调的高精度高稳定脉冲驱动电源。该电源以大功率场效应晶体管为核心, 通过现场可编程门阵列产生的高精度时序波形来完成单脉冲内的上升沿调控和栅极控制电压补偿, 通过微控制器结合电流采样的闭环控制方案实现重频运行下的电流高稳定输出。结果表明, 在输出电流100 A、脉冲宽度400 μs、重复频率1 kHz的最大功率输出驱动二极管负载时, 驱动电流上升沿过冲幅度小于0.5%、单脉冲内电流衰减小于0.2%、重复率脉冲不稳定度小于0.1%;在同样输出条件下驱动半导体激光器, 其在单脉冲内光功率过冲小于2%, 重复光脉冲不稳定度小于0.2%。该研究有助于提高脉冲电源脉冲电流稳定性, 对现有脉冲电源结构的改进具有一定的参考意义。     

低频/甚低频电磁脉冲测量系统研究

为了准确地测量电磁脉冲（electromagnetic pulse,EMP）的波形,开展低频/甚低频（low-frequency/very low-frequency,LF/VLF）EMP的形成和传播机理研究,识别不同EMP的特征,并以此为依据来识别、确认雷电及核爆炸等现象,提出了一种高分辨率的EMP原始波形测量系统方案,同时针对LF/VLF这一较低的频段提出了一套有效的系统标校方法,实现了对EMP的连续、准确测量和快速有效判别,并能通过网络实时上传数据.系统采用正交环磁场天线和平板电容电场天线实现信号的接收,设计了低噪声高保真的信道调理电路和高速数据采集电路来实现信号的采集,利用高精度的授时模块为EMP信号标记时间戳,最后结合多点监测波形实现EMP定位估计.实测结果表明:该系统能够给出高分辨率、高精度的LF/VLF EMP波形;利用该系统组网可以实现远距离EMP源的定位,定位精度与目前近距离的定位手段相当.通过长期的运行,验证了该系统具有高可靠、低失真、判别准确、实时性强等特点.