Shielding Characterization of Metallic Enclosures With Multiple Slots and a Thin-Wire Antenna Loaded: Multiple Oblique EMP Incidences With Arbitrary Polarizations

Shielding effectiveness (SE) of metallic rectangular enclosures with thin slots and a thin-wire antenna loaded by an impedance, illuminated by multiple electromagnetic pulses (EMPs) simultaneously, is investigated using a hybrid finite-difference time-domain (FDTD) method. In order to enhance the simulation efficiency of the FDTD algorithm, accurate formulas for handling multiple thin slots, a thin-wire antenna, and a lumped network are integrated together. Numerical results show that for real metallic enclosures, their shielding performance is very sensitive to the variations in direction and polarization angle of the incident EMPs. However, at a given frequency, the resistance and inductance loaded at the terminal of a thin-wire antenna have little effect on the SE level. For two, three, as well as more EMP incidences, common-frequency interferences will result in strong inner field resonance in the enclosure.      

一种UWB雷达脉冲信号发生器的设计

介绍了UWB雷达的人体生命探测系统的工作原理,比较了几种窄脉冲产生方法的优缺点,详细分析了雪崩三极管原理,利用雪崩三极管的雪崩特性实现了超宽带雷达窄脉冲的产生。通过研究分析典型的脉冲产生电路,给出了产生人体生命探测系统的脉冲信号发生器的电路,最后由实验仿真结果可得,电路可生成脉宽为皮秒级的双极性脉冲,脉冲的峰-峰值达2...     

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.     

Scattered EM Field Responses of Canonical Scatterers Illuminated by an Impulse-Radiating Antenna (IRA)

This paper investigates the possibility of using the impulse-radiating antenna (IRA) as both a transmitter and receiver of electromagnetic energy for the purpose of target identification. Of specific interest is estimating the induced open-circuit voltage at the IRA's source terminals, when it is illuminated by the scattered EM field from simple conducting bodies excited by an incident field from the same IRA acting as a transmitter. In this study, several different canonical scatters are considered, including thin wires, spheres, conducting boxes, and an infinite conducting plate. For a 7 kV pulse excitation of the IRA, received peak transient voltages at the antenna ranged from a few volts to about 400 volts, depending on the scatterer.     

Transient Currents Induced on a Metallic Body of Revolution by an Electromagnetic Pulse

A numerical technique is presented that may be used to predict the current induced on a thin metallic body of revolution excited by an electromagnetic pulse. Examples are given. Introduced here is the use of the radiation condition in a finite difference solution. This development alleviates the requirement that finite difference techniques be applied to a bounded region of space.     

Rectangular Waveguide With Metallic Nanostructure Driven by Magnetic Field

The changes in the propagation constant of the TE₁₀ mode of a rectangular waveguide with a metallic nanostructure, occurring under an external magnetic field have been investigated. Expressions for complex reflection and transmission coefficients have been derived. The dependence of the reflection coefficient upon the intensity of the external magnetic field is analyzed. It is shown that the experimental values of the propagation constant or the reflection and transmission coefficients can be used to estimate the value of the microwave magnetoresistance of nanostructures. Experiments on the measurement of the reflection and transmission coefficients in a waveguide with an (Fe/Cr)n nanostructure have been performed in millimeter and centimeter wave bands.     

Design of Low-Pass Elliptic Filters by Means of Cascaded Microstrip Rectangular Elements

A new method for synthesizing nonredundant low-pass elliptic filters in a microstrip configuration is presented. The realization consists of the cascade connection of proper rectangular elements, each one corresponding to four reactive elements of the lumped-constant prototype. This allows an effective control of parasitic and unwanted reactance which results in the possibility of realizing higher order filters with cutoff frequencies up to X-band. Fifth- and seventh-order filters were fabricated on alumina substrates showing very good performance, particularly in the passband.     

脉冲平面波斜入射旋转对称体时域电磁散射特性分析

介绍了一种运用旋转对称时域有限差分算法进行电磁散射问题分析的方法。对脉冲平面波在圆柱坐标系下进行分解,应用总场/散射场连接边界引入入射波,采用PML吸收边界条件。运用这种方法分析了有限长度闭合金属圆柱体的散射问题,通过与矩量法分析结果的比较,验证了该方法的正确有效性。     

Analysis of an Inhomogeneously Loaded Rectangular Waveguide with Dielectric and Metallic Losses

A dieletric loaded rectangular guide (Fig. 1) is analyzed taking into account the losses of the line, the substrate, and the metallic shield. For this study, Schelkunoff's method is used in considering the propagation modes as a convenient combination of coupled modes of the empty waveguide. Computations and experimental measurements are made for two different lines.     

用于超宽带穿墙雷达的窄脉冲产生技术

用于超宽带穿墙雷达的脉冲产生技术是一种无载波极窄脉冲产生技术,在无线电通信领域有着广阔的应用前景。提出了使用延时芯片和ECL门产生极窄脉冲的方法,并对其产生原理做了理论分析。设计了原理框图和电路图,最后给出并分析了试验结果。     

带孔缝矩形金属腔体屏蔽效能研究

针对带孔缝矩形金属腔体在电磁辐射下的屏蔽效能问题,利用基于时域有限积分法的电磁仿真软件CST,建立了平面波辐照条件下含孔缝金属腔体的耦合模型,重点研究了电场极化方向,腔体材料,矩形孔缝的长度、宽度和深度,孔缝填充介质介电常数及其厚度等参数对屏蔽效能的影响规律.研究结果表明:典型金属材料对屏蔽效能的影响差别不大,垂直于电场极化方向的孔缝边长更能影响腔体的屏蔽效能,孔缝尺寸会影响矩形金属腔体的谐振点,孔缝深度能够通过衰减入射波在一定程度上影响屏蔽效能,孔缝填充介质会降低屏蔽效能,介质厚度及其介电常数会影响屏蔽效能峰值点.研究结果对金属腔体的电磁兼容设计有一定的指导意义.     

贴片-网栅级联二阶宽带带通频率选择表面设计

采用贴片谐振型与网栅感性型单元级联组合的方法,设计了一款二阶宽带带通频率选择表面(FSS),在0°～45°入射角范围内,通带为8.0～12.6 GHz,覆盖X波段,平均插入损耗小于1 dB。该结构由两层贴片型单元阵列和一层感性金属网栅级联组成,优化确定的FSS单元尺寸为0.136 λ×0.136 λ(λ为工作波长)。设计的FSS单元为小型化对称结构,采用等效电路法和全波电磁仿真,对该FSS结构的工作机理和TE/TM极化波在不同入射角的传输频率响应进行分析。研究结果表明在0°～60°入射角范围内传输频响具有较好的角度稳定性和极化一致性,所设计的单元级联结构的层间耦合小,弱化了单元对齐的影响,其对带通曲面天线罩设计具有应用价值。     

非辐射边馈电的宽带双层微带贴片天线

介绍了一种非辐射边馈电的宽带双层微带贴片天线单元,并对其参数特性进行了仿真研究,结果表明,通过在寄生贴片上开3～5个与极化方向相平行的缝,可有效抑制天线的交叉极化,同时改善天线的阻抗带宽。相比传统双层微带贴片,该天线单元的阻抗带宽可提高3%以上,而交叉极化指标相当。当该单元应用于阵列天线设计时,可简化馈电网络,便于实现宽带、高效、大扫描角的微带共面馈电天线阵。对X波段8×8单元实验小阵的测试结果表明,该天线在17.6%的频段内具有良好的交叉极化性能及较高的工作效率。     

Accurate Characterization of Shielding Effectiveness of Metallic Enclosures With Thin Wires and Thin Slots

In many electrical and electronic systems, metallic enclosures are used to provide electromagnetic shielding. These enclosures normally contain thin wires, thin slots, and frequency-selective slots (FSS) that degrade the shielding effects. In this paper, integrated FDTD formulations are developed that can model both subcellular thin slots and thin wires simultaneously. The formulations are shown to be capable of accurately predicting shielding effectiveness and inner field distributions of a metallic enclosure in both the frequency- and time-domains when subject to a high-power electromagnetic pulse.      

Design of Stacked Rectangular Dielectric Resonator Antenna for Wideband Applications

Wireless Personal Communications - In this article, we present the study to improve the bandwidth of the dielectric resonator antenna (DRA) excited by aperture coupled feed by using a stacked DRA...     

Novel Parameter Estimation of Double Exponential Pulse (EMP, UWB) by Statistical Means

High-power electromagnetic environments, such as the high-altitude electromagnetic pulse (HEMP) and the ultrawide-band (UWB) pulses, pose dangerous threats to electronic systems. Such pulse shapes are often described physically by the characteristic parameters: the rise time t_r, pulse width t_fwhm and maximum electric field strength E_max, and mathematically by the double exponential function with characteristic parameters alpha, beta ,kappa . and E₀. In practice, it is very necessary to transform the two groups of parameters into each other. In this paper, a novel relationship between the two groups of parameters is established by statistical means. This method utilizes only four assistant variables to realize the transform, and the overall estimation error is less than 2.0%.     

An Experimental Investigation of the Rhombic EMP Simulator Under Pulse Excitation

The rhombic simulator excited by a pulse generator is investigated experimentally. The voltage pulse at the driving point of the simulator and the associated current pulses that travel along the conducting tubes that form the rhombus have been measured with different loads. The complex sequence of electromagnetic pulses (including the incident pulse, the reflected pulses from the load, and other reflection points) have been measured on the metal ground plane. The origin (localization) of each pulse has been carried out. From the Fourier transformation of the waveforms in the time domain, the spectrum of the electromagnetic pulse in the frequency domain is obtained. It is shown that the characteristics of the simulator with the two types of excitation (continuous wave and pulse) are consistent.     

VLSI Implementation of the Multistage Detector for Next Generation Wideband CDMA Receivers

The multistage detection algorithm has been proposed as an effective interference cancellation scheme for next generation Wideband Code Division Multiple Access (W-CDMA) base stations. In this paper, we propose a real-time VLSI implementation of this detection algorithm in the uplink system, where we have achieved both high performance in interference cancellation and computational efficiency. When interference cancellation converges, the difference of the detection vectors between two consecutive stages is mostly zero. Under the assumption of BPSK modulation, the differences between the bit estimates from consecutive stages are 0 and ±2. Bypassing the zero terms saves computations. Multiplication by ±2 can be easily implemented in hardware as arithmetic shifts. However, the convergence of the algorithm is dependent on the number of users, the interference and the signal to noise ratio and hence, the detection has a variable execution time. By using just two stages of the differencing detector, we achieve predictable execution time with performance equivalent to at least eight stages of the regular multistage detector. A VLSI implementation of the differencing multistage detector is built to demonstrate the computational savings and the real-time performance potential. The detector, handling up to eight users with 12-bit fixed point precision, was fabricated using a 1.2 m CMOS technology and can process 190 Kbps/user for 8 users.     

Frequency Response of Multiconductor Transmission Lines Illuminated by an Electromagnetic Field

A well-known result [1], [2] for the response of a two-wire transmission line illuminated by a nonuniform electromagnetic field is extended to multiconductor lines. A simple matrix equation for the currents induced in arbitrary termination networks is obtained. Air Development Center.