V-conical antenna

A new angular antenna called the V-conical antenna was investigated. The characteristics of the antenna are frequency-independent, and the electromagnetic fields are pure spherical waves (transverse electromagnetic mode) even in the near region. The theoretical analysis makes use of conformal mapping. Closed-form solutions for the fields, currents, and characteristic parameters are obtained. The formulas are simple and precise. An experimental study of the antenna was conducted under pulse excitation. The shape of the measured electric-field pulses is the same as that of the source pulse from a picosecond pulse generator. The measured field patterns are very close to those predicted by the theory. Such a structure with a tapered resistive termination is an ideal directional pulse antenna or electromagnetic pulse simulator     

Theoretical Analysis of the Rhombic Simulator Under Pulse Excitation

An analysis is given of the electromagnetic pulse generated in the space between the wires of a rhombic simulator by pulses of current traveling along the wires. After the mechanism of pulse excitation is clarified with the help of measured results, the electromangnetic pulse is investigated in terms of a current pulse with known shape that travels along the rhombic wires. The calculated pulse sequences agree very well with the measured ones. The "subpulse" radiated by each small segment of the wires as the current pulse traverses it is also studied. The time delays of the sequence of subpulses play an important role in the formation of the complete electromagnetic pulse. The amplitudes of the subpulses are relatively less important.     

The Matching Between an EMP Simulator and the Pulse Generator

The input properties of the parallel-plate Harvard EMP simulator (HES) and the means for matching the simulator to the pulse generator have been studied in detail. Due to mismatching, multiple reflections occur between connections, and the originally generated single pulse becomes a complicated pulse sequence which includes not only the main impulse, but also many parasitic pulses. The parasitic pulses can be eliminated by meeting the conditions for match, or they can be separated from the main pulse by increasing the electrical distance between the simulator and the generator. The input properties of the simulator can be represented in terms of an "apparent impedance" which depends on the part of the pulse sequence under consideration. For the main incident pulse, the apparent impedance is a resistance close to the characteristic impedance of the simulator for CW operation at low frequencies.     

超宽带纳秒脉冲在带通滤波器中传输特性研究

根据超宽带(UWB)纳秒电磁脉冲的基本特性,采用模拟计算仿真与实验研究方法,研究了超宽带纳秒电磁脉冲信号通过微波接收机带通滤波器的时域、频域传输特性,初步认识了超宽带纳秒电磁脉冲通过带通滤波器传输特性规律,它是对传统连续波(CW)信号与脉冲调制信号通过微波带通滤波器传输特性技术的补充和完善。该研究成果为将来开发超宽带纳秒电磁脉冲在各类接收机中的应用提供技术基础。     

强激光打靶产生电磁脉冲特性与传导防护研究

为了降低电磁脉冲的场强大小,加强强激光打靶产生电磁脉冲的传导防护性能,提出了强激光打靶产生电磁脉冲特性与传导防护研究。由于强激光打靶产生电磁脉冲对各种电子设备和电气设备都会造成一定威胁,采用双指数函数,分析了强激光打靶产生电磁脉冲的时域波形频谱,完成了强激光打靶产生电磁脉冲的特性研究;为了消除强激光打靶产生的电磁脉冲波,分析了电磁脉冲理想滤波器的衰减特性,并利用电磁脉冲滤波器的衰减计算公式,设计了电磁脉冲滤波器;利用电磁脉冲滤波器的衰减特性,在强激光打靶产生电磁脉冲过程中安装了屏蔽体,通过计算强激光打靶产生电磁脉冲的传导防护效能,实现了强激光打靶产生电磁脉冲的传导防护。仿真结果显示,提出的传导防护方法与其他两种方法相比,电磁脉冲的传导防护性能更好。     

面向IC芯片结构高速数字传输线特性三维电磁场时域模拟器

本文介绍一种采用对称凝缩节点传输线阵方法研制成面向集成电路芯片结构的高速数字传输线特性三维电磁场时域模拟器。模拟器能模拟高脉冲在ＩＣ芯片上由任意矩阵结构组成的共同传输线中的时域全波传输过程。     

时频空交叠信号的脉内调制类型识别算法

复杂电磁环境下的雷达信号分选技术充分利用被侦察信号的特征信息,把分属于不同信号源的雷达脉冲流分离开来。随着脉冲流密度的增加,出现了一些在时频空3个维度上均严重交叠的脉冲,这些脉冲的辐射源信息差别很小,以至于识别算法无法正确将它们区分,进而造成脉冲丢失或错误识别,使得信号分选的性能大大下降。以6种常见的脉内调制类型脉冲为研究对象,针对脉冲之间两两交叠的情况,提出了基于部分快速傅里叶变换算法的时频空交叠信号脉内调制类型识别算法,并通过一系列仿真分析了算法的性能,证明了算法能够有效地分辨频域和空域高度重叠但时域不完全重叠的信号脉冲流,提高信号分选的性能。     

A planar triangular monopole antenna for UWB communication

A planar triangular monopole antenna (PTMA) is presented for high-frequency structure simulator ultra-wideband (UWB) communication. The high-frequency structure simulator three-dimensional electromagnetic solver is employed for design simulation. A printed PTMA has been realized by using the FR-4 printed circuit board substrate. The measured voltage standing wave ratio is less than 3 from 4 to 10 GHz. In the UWB communication frequency range, the measured phase distribution of the input impedance is quite linear and the H-plane patterns are almost omni-directional. The Kirchhoff's surface integral representation was adopted in the developed finite-difference time-domain code to compute the far field distributions from the near filed ones in time-domain. This is to investigate the radiated power density spectrum (PDS) shaping to comply with FCC emission limit mask. The effect of various source pulses (first-order Rayleigh pulses with /spl sigma/ of 20, 30, and 50 ps) on the radiated PDS shaping is also studied.     

Electro-Optical System for EMP Measurement

An electro-optical system is described for measuring the E-field component of electromagnetic pulses (EMP) produced by an EMP-simulator. Typical rise time of these pulses is down to 10 ns, measured E-field strength from 1-500 kV/m. The measurement device consists of a He-Ne-Laser as the light source, fiber optics as the transmitter with a length of up to some hundred meters, a Pockels-cell with two polarizers as the sensor modulating the light intensity in dependence of E-field strength, and a photodiode with preamplifier and storage oscilloscope as the detector. The wide E-field range can be measured by capacitively coupling the E-field to the Pockels-cell via pairs of plane antennas with variable area. Measurements are shown of pulses produced by a laboratory simulator and a field simulator.     

Currents and fields of thin circular and elliptical loops

Approximate solutions for the current of thin circular and elliptical loops have been determined on the basis of an asymptotic antenna theory. The fields at and around the center have been calculated to illustrate the broadband behavior of these structures when used as electromagnetic pulse (EMP) simulators. Fields calculated with this approach and those measured in an actual EMP simulator are compared. The comparison indicates that the model presented might be adequate for describing the salient features of the fields of a real system and could provide an alternative to experimental field mapping efforts     

减小雷达环境模拟器脉冲丢失概率方法

雷达信号环境模拟器在模拟复杂电磁信号环境时,会产生大量脉冲丢失,这与实际战场环境不符,同时对电子侦收也存在一定影响。采用直接数字合成（DDS）技术可生成任意波形,解决脉冲丢失问题。     

基于IRA天线的辐射波模拟器天线辐射性能研究

将通常用于超宽带领域的IRA天线应用到辐射波电磁脉冲模拟器中,提出一种基于反射器脉冲辐射天线的核电磁脉冲辐射波模拟器,分析其天线结构,给出四种馈臂形式,通过仿真比较了四种馈臂形式天线的辐射效率、远场和近场波形以及频率增益特性。结果表明:该天线的低频辐射效率有待进一步提高;具有锥形渐缩形式馈臂的天线能产生较好的远场和近场波形。IRA天线相较笼形天线具有体积小、方向性好等优点,如果能进一步提高其低频辐射性能,IRA天线将成为理想的辐射波模拟器天线。     

An Experimental Investigation of the Distribution of Current And Charge Induced on a Tubular Conducting Cylinder by an Electromagnetic Pulse

The distribution of current and charge induced on a tubular cylinder by an electromagnetic pulse (EMP) is investigated experimentally in the Harvard parallel-plate EMP simulator (HES). The pulse shapes of the current and charge induced on the surface of the cylinder are measured. After Fourier transforms of the observed pulse shapes are taken, the distributions of the several frequency components on the surface are obtained. The measured distribution of each frequency component is then compared with the theoretical distribution calculated using Kao's method.     

Response of an overhead wire near a NEMP simulator

The response of an overhead wire illuminated by a simulated nuclear electromagnetic pulse (NEMP) was experimentally investigated. The wire is 70 m long, 7 mm in diameter, and situated 5 m above the ground. It is located 20 m away from a hybrid-type EMP simulator. The simulator is a resistively loaded elliptical loop structure with its pulse generator located 20 m above the ground. The overhead wire is terminated with various combinations of short circuit, open circuit, and characteristic impedance at the two ends, and the current response is measured at one end and in the middle. The measured responses are compared with calculated values from available analytical models     

HEMP模拟器的改进及测量探头的设计

针对国际电工委员会发布的高空核电磁脉冲（HEMP）波形新标准,对有界波电磁脉冲模拟器进行了改进：研制了新型纳秒液体开关,设计、制作了D-dot型电场监测探头,构成了一套完整的快前沿HEMP抗扰度实验系统。试验结果表明,改进后的模拟器可产生前沿小于2.0 ns,半峰宽25 ns,峰值50 kV/m的双指数电磁脉冲;通过与瑞士Montena公司生产的SEG2G型电场探头试验测量结果的比较,表明本文研制的测量系统完全满足设计要求。     

太赫兹波在介质中传播的FDTD分析

时域有限差分法是电磁场领域中应用最为频繁的数值方法之一,它可以有效地处理复杂媒质中颗粒对电磁脉冲信号的散射问题,以及超宽带电磁脉冲信号在色散媒质中的传播问题。几乎所有介质,无论其在太赫兹（THz）波段是否有吸收峰,对太赫兹波的传播都有影响。研究太赫兹波在介质中的传播情况,对优化太赫兹系统,分析与设计太赫兹应用技术有重要意义。本文模拟了太赫兹波在散射介质中的传播,说明了太赫兹波在内弹道干涉测速应用中的可能性;模拟了太赫兹脉冲在色散介质中的传播情况,为太赫兹时域光谱系统中晶体选择提供依据。     

静电放电电磁脉冲均匀辐射场模拟

为了研究静电放电电磁脉冲（ESDEMP）的特性,利用传统的静电放电电磁脉冲产生方法,通过静电放电模拟器在静电放电抗扰度试验平台上放电,产生了静电放电电磁脉冲,并测出了静电放电电磁脉冲的时域波形和频谱。在研究电磁脉冲模拟器的基础上,首次通过ESD模拟器和GTEM室的结合,在GTEM室内产生了均匀的、重复性和线性好的ESDEMP。实验表明,用TEMP室、GTEM室等大型装置产生均匀静电放电电磁脉冲辐射场的方案是可行的。     

Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse

The development of antenna theory for nonsinusoidal electromagnetic waves has been based on the idealized rectangular pulse. In practice, an antenna that is designed to operate in the mode of an electric hertzian dipole would radiate a pulse that best approximates a Gaussian one when the driving current consists of a linear transient. The principle of radiation of nonsinusoidal electromagnetic waves with the time variation of Gaussian pulses is discussed. The properties of the Gaussian pulse are presented, i.e., the autocorrelation function, energy spectral density, and spectrum. Antenna patterns, such as peak-amplitude pattern, peak-power pattern, energy pattern, and slope pattern are derived for a Gaussian pulse received (or radiated) by a linear array antenna. Computer plots of the derived antenna patterns are presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for a rectangular pulse     

Ultra-Wideband Waveform Generator Based on Optical Pulse-Shaping and FBG Tuning

We propose and demonstrate experimentally a prototype for ultra-wideband (UWB) waveform generator based on optical pulse shaping. The time-domain pulse shape is written in the frequency domain, and a single-mode fiber performs frequency-to-time conversion. A U.S. Federal Communications Commission (FCC)-compliant power efficient pulse shape is inscribed in the frequency domain by a fiber Bragg grating (FBG) with an excellent match between optimized and measured pulses. Two other popular UWB pulse shapes (Gaussian monocycle and doublet pulses) are achieved by proper tuning of two FBG-based variable optical filters. A balanced photodetector removes an unwanted rectangular pulse superimposed on the desired waveform, assuring compliance at low frequency.