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1.
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.   相似文献   

2.
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.  相似文献   

3.
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.  相似文献   

4.
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.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
用于超宽带穿墙雷达的窄脉冲产生技术   总被引:1,自引:0,他引:1  
黄堂森 《电子科技》2007,(2):23-24,28
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。  相似文献   

8.
9.
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...  相似文献   

10.
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.   相似文献   

11.
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 tr, pulse width tfwhm and maximum electric field strength Emax, 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%.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
Modeling of an EMP conducted environment   总被引:7,自引:0,他引:7  
The International Electrotechnical Commission (IEC) decided in 1988 to produce a civil standard on the electromagnetic effects of a high altitude EMP (HEMP). Different documents pertaining to the radiated environment and to specifications and test methods have been elaborated and are circulated. A standard conducted environment dependent on many parameters is, however, more difficult to define. The authors present a probabilistic approach which has been adopted to define a typical current shape for the conducted environment. The distribution functions of the peak current value for horizontal and vertical polarizations based on 1710 calculated cases reflecting a variation of the elevation and azimuthal angles from 0 to 90° are presented and discussed  相似文献   

15.
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.  相似文献   

16.
The work presented in this letter demonstrates that nonuniform transmission lines (NUTLs) can be used for pulse shaping applications in ultra wideband pulsed systems and presents an approach to their design for this application. The pulsed waveforms generated are modified Hermite polynomials and encoded pulse trains thereof and are characterised by a broad bandwidth ranging from near DC to over 10 GHz and relatively long temporal duration in the region of nanoseconds. These pulses are more mathematically complex and at least three times higher bandwidth than previously has been reported in the literature. It is also believed to be the first time that modified Hermite polynomial pulses have been generated in practice. The NUTL design approach is verified by test structures fabricated on FR4 circuit board. The results demonstrate that NUTLs, which are completely passive structures, allow generation of complex pulse shapes in applications requiring fast, transient waveforms.   相似文献   

17.
提出并实验验证一种级联啁啾光纤光栅反馈半导体激光器产生宽带、无时延混沌激光的方法.在该方法中,级联啁啾光纤光栅的高色散引入不规则的外腔模式,破坏了外腔模式谐振,进而消除混沌信号的时延特征.此外,不规则的外腔模式与激光器内部模式拍频,引入了新的高频振荡,进而增强混沌信号的带宽.对比研究了单个与级联啁啾光纤光栅反馈系统中色...  相似文献   

18.
由于群速度失配的影响,飞秒光脉冲在感应到FONPS(级联五阶非线性相移)的同时,将不可避免地发生脉冲畸变.通过理论分析及数值模拟,提出了使级联五阶非线性过程运行在较大相位失配条件下的解决方案,成功地消除了脉冲畸变.并且借助于该过程中倍频效率的提高,有效地补偿由于相位失配量的增大所造成的FONPS的下降,实现飞秒基频光脉冲在感应到大的FONPS的同时无脉冲畸变发生.  相似文献   

19.
陈旗  曹汉强  方标  黄高明 《信号处理》2012,28(6):900-906
压缩感知技术可以用来实现对非合作宽带信号的欠采样快速处理。宽带脉冲压缩雷达能够有效解决雷达探测距离和距离分辨力的矛盾,在探测领域得到了广泛应用,为实现对非合作宽带脉冲压缩雷达信号的快速欠采样接收处理,本文首先开展了信号稀疏分解与重构算法研究,通过对贪婪算法、凸松弛类算法、组合类算法三大算法进行对比分析,选用了运行速度快且重构精度高的正交匹配追踪(OMP)算法针对非合作宽带脉冲压缩雷达信号进行压缩感知仿真分析。仿真结果表明:在一定信噪比条件下,OMP算法完全能够实现对非合作宽带脉冲压缩雷达信号的欠采样和信号重构,从而实现了对非合作宽带雷达信号的欠采样处理,为处理非合作超宽带雷达信号提供了很好的理论指导。  相似文献   

20.
The quasi-likelihood, maximum-likelihood, and quasi-optimal algorithms for estimating the instants of appearance and disappearance of an optical pulse with the rectangular intensity profile of an unknown height are synthesized and analyzed. The losses in estimation accuracy due to the a priori unknown intensity of the optical pulse are found.  相似文献   

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