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简要地概述的设计无载波脉冲探地雷达天线的理论论据和方法,并讨论了天线的类型的技术现状,对一种比较实用的无载波脉冲探地雷达天线的近地面工作特性进行了实验测试。结果表明,天线的性能在一定程度上受土壤特性的影响,天线向地下传输的能量与天线距离地面的高度h有很大关系。在h≤40cm时,随着天线高度h的升高,天线向地下传输的能量急剧地减小。借助于该实验,还对天线辐射出的无载波脉冲在土壤中的传播特性进行了研究 相似文献
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无载波脉冲探地雷达收发技术的研究 总被引:1,自引:0,他引:1
本文对无载波探地雷达的关键部件-收发技术进行了研究。首先分析了取样频率,取样门管参数对取样头性能的影响,设计了发射天线所需要的高速脉冲源和高速取样头以及收发双工开关,最后对取样过程的稳定问题进行了讨论。实验证明了我们研制有取样头性能良好,它可以用在无载波探地雷达系统中作为信号采集器。 相似文献
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本文研究地下塑料圆盘和管道的探测,指出了探地雷达和普通雷达的区别。叙述了为研制一种可靠的探测系统所进行的广泛深入的工作,该系统为工作于时域的无载波系统,辐射一个快速上升时间脉冲以照射地面。 相似文献
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频率步进方法是探地雷达技术的工作体制之一,与时域无载频脉冲体制的探地雷达技术相比,在探测性能上具有较多的优越性.本文在简述其工作原理的基础上,介绍了作者研制的一种频率步进探地雷达系统,该系统主要用于对地雷目标进行三维成像探测.在研制该雷达系统过程中,对已有的反对称Vivaldi天线提出了改进设计.实验测量结果表明,本文研制的反对称Vivaldi天线与传统的同类天线相比,性能更加优越.同时,为了得到更加清晰的地雷图像,本文还分别引入了f-k偏移成像方法和合成孔经雷达(SAR)处理技术对雷达探测信号进行处理,得到了满意的结果.探测实例表明,频率步进探地雷达系统能够实现对浅层地下地雷目标的高分辨率三维成像探测. 相似文献
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目标识别是雷达探测领域研究的难点问题,本文利用无载频脉冲探地雷达系统对有耗媒质中细长导线状和环状金属目标的瞬态散射特性进行了实验测量,并利用极点展开理论对谐振现象的产生给予了分析和讨论。在瞬态脉冲激励下,有耗媒质中的目标能够产生外部振荡现象,目标谐振时雷达接收信号的幅值比非谐振时大得多。谐振信号的产生与目标形状和特性、媒质参数、激励脉冲的宽度和天线极化特性等因素有关。 相似文献
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FDTD分析探地雷达天线的辐射特性 总被引:4,自引:0,他引:4
探地雷达系统一般采用超宽带短脉冲信号,因而其天线系统必须具有较好的宽带性能。只有几种类型的宽带天线能够用于探地雷达系统中,如电阻加载的蝶形天线、TEM喇叭天线及其变形形式。本文将给出一种新型的探地雷达天线,该天线为置于镜像面上且具有离散指数电阻加载的单偶极子。文中将采用FDTD计算和分析该天线在自由空间和有耗媒质上方时的辐射特性。结果表明,通过选择一定的电阻加载形式,可使天线具有较好的辐射波形,从而能够满足实际探地雷达的需要。最后,通过地下目标散射场的理论结果和实验结果说明了本文所采用方法的正确性。 相似文献
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脉冲探地雷达的模拟计算 总被引:1,自引:0,他引:1
本文在给出Debye型色散媒质中2.5维时域有限差分法(2.5D-FDTD法)迭代公式的基础上,对无载频脉冲波在不同色散媒质中的传播特性进行了计算,分析了脉冲产生畸变的原因,并提出对部分畸变脉冲进行整形的方法。分别对地下单体目标和群体目标的雷达回波电平图进行了模拟计算,并与实际无载频脉冲探地雷达的探测结果进行比较,二者有较好的一致性,证实了本文所给计算公式的正确性。另外,还分析了土壤参数对雷达探测深度和分辨率的影响。 相似文献
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无载频脉冲探地雷达性能分析及其FD—TD法数值模拟计算 总被引:1,自引:0,他引:1
探测深度和分辩率是探地雷达的两项重要指标。本文分别对无载频脉冲探地雷达的探测深度和分辩率进行了分析,指出了影响雷达探测深度和分辩率的因素,并利用2。5维时时有限差分方法对雷达的探测性能进行了数值模拟计算,给出了地下单体目标和多体目标的回波信号电平图,并将部分计算结果与实验测试结果进行了对比,二者具有好的一致性。 相似文献
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探地雷达探测干旱区潜水埋深研究 总被引:1,自引:0,他引:1
结合探地雷达技术理论与包气带土壤水分分布特性分析了探地雷达测定潜水埋深的技术原理,并对天线频率、地下水埋深、毛细水带等影响探测结果精度的客观因素进行了误差分析。为验证探地雷达技术应用于干旱区潜水埋深探测的有效性,选取神东矿区松散层为第四系风积沙覆盖的两个工作面,潜水位平均埋深分别为41m和10m,采用探地雷达对区域的潜水埋深进行了野外探测,并利用工作面上方测线附近水井的水位实测值进行验证。结果表明利用探雷达能有效地测定该工作面处地下潜水埋深,探测精度与水位埋深和采用的天线主频等因素有关。在确定潜水位埋深时,还需考虑土壤毛细水带高度的影响。 相似文献
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The optimum transient radiation from an arbitrary antenna 总被引:2,自引:0,他引:2
Pozar D. Schaubert D. McIntosh R. 《Antennas and Propagation, IEEE Transactions on》1984,32(6):633-640
Bounds on the optimum transient radiation from an arbitrary antenna enclosed by a spherical surface of specified size are presented. The optimization criterion is either maximization of the radiated electric field amplitude at a specified time and far-zone position, or maximization of the radiated energy density in a specified time interval for a particular far-zone position. The latter optimization results in the prolate spheroidal wave functions. In both cases, the total energy radiated by the antenna is constrained to be 1 J, and the antenna excitation is assumed to be bandlimited. The performance of the optimum arbitrary antenna is compared to that of optimized practical antennas, such as dipoles and arrays of dipoles. The effect of a sidelobe constraint is also studied. 相似文献
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Solutions are presented for the optimal electric field waveforms radiated by an arbitrary ultrawideband (UWB) antenna. Optimization criteria include maximization of the electric field amplitude at a particular time and location, or maximization of energy density over a specified time interval at a particular location. Assuming bandpass signals, constraints are placed on the total radiated energy, the Q of the antenna, and the size of the antenna. The solution is developed using a spherical mode expansion of the fields radiated by an arbitrary antenna enclosed by a spherical mathematical surface, and optimized using variational methods. A closed-form result is obtained for the case of amplitude maximization, while an integral equation must be solved numerically for the case of energy maximization in a time interval. An interesting result from these solutions is that the shapes of the optimal radiated field waveforms are largely independent of the size of the antenna. The solutions also indicate that the antenna characteristics that provide optimum field amplitude or energy in the transient case are identical to those associated with maximum gain in the CW case. 相似文献
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A linearized hydrodynamic theory and potential function technique arc used to formulate the theory of a corner-driven loop antenna immersed in a warm plasma. The theory explains some of the experimental observations obtained from impedance measurement of a loop antenna on the Ariel 3 satellite. The far-zone fields and the normalized radiated power for different antenna sizes are calculated. The results suggest that much of the radiated energy is radiated in longitudinal plasma waves 相似文献
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The simulation of a plasma sheath using an artificial dielectric is studied in this investigation and is applied to an antenna geometry which is similar to some configurations encountered in aerospace applications. The antenna configuration is equivalent to a horn in an infinite ground plane with an unbounded plasma layer in front of the horn. The plasma layer is simulated by a rodded medium, and the radiation patterns of the antenna system are studied experimentally at 9, 10, and 11 Gc/s. Two constructions of rodded media are utilized in the pattern measurements. The experimentally determined radiation patterns have a secondary maximum associated with the properties of the plasma sheath. More energy is radiated in the OFF-axis region when the plasma sheath is present. 相似文献
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One phase of the electromagnetic compatibility program is the determianation of the electromagnetic energy actually radiated into space by an antenna. Methods have long been established, or proposed, for measuring the power output of a transmitter, the antenna impedance, and the antenna-radiation pattern. However, very little definitive work has been published regarding the methods for computing the transmitter energy coupled to the antenna and radiated at harmonic and spurious frequencies. It is the purpose of this paper to reduce to a simple form the equations for determining the power absorbed by an antenna connected through a coaxial transmission line to a transmitter. Most discussions of transmission-line-power transfer assume the matched conditions so universally desired at the operating frequency. When harmonic and spurious frequencies are considered, both the transmitter and the antenna are likely to be poorly matched to the transmission line and to each other. This paper points out what measurements need to be made and gives the functional relations necessary to compute the power radiated under unmatched conditions. Since the actual power coupled to the antenna in a given instance may be critically dependent upon the exact length of transmission line, some means must be available to take this into account. The expressions derived give the maximum and minimum power that will be absorbed, and also give the probability that any specified intermediate power will be exceeded if a random choice of transmissionline length is used. 相似文献
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Adaptive wire bow-tie antenna for GPR applications 总被引:2,自引:0,他引:2
Lestari A.A. Yarovoy A.G. Ligthart L.P. 《Antennas and Propagation, IEEE Transactions on》2005,53(5):1745-1754
In this paper, the basic design of an adaptive ground penetrating radar antenna is introduced. The antenna is able to adapt its input impedance to a variation in the antenna elevation and soil type to keep reflections at the antenna's terminal minimum. As a result, energy transfer from the generator to the antenna is maximized, which in turn maximizes the energy radiated by the antenna into the ground for different antenna elevations and soil types. The antenna is based on a wire bow-tie structure with variable flare angle for adjusting the antenna's input impedance. The flare angle variation is realized by short-circuiting the gaps separating the wires from the feed point of the antenna, for which electronic switching devices such as PIN diodes could be used to allow fast and convenient control of the antenna's flare angle. 相似文献
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Probe compensated near-field measurements on a cylinder 总被引:1,自引:0,他引:1
A new method is developed for determining the farfield pattern of an antenna from probe compensated near-field measurements over the surface of a right circular cylinder enclosing the antenna. The method is derived by first expanding both the field radiated by the antenna and the field radiated by the measurement probe, when it is used as a transmitter, into cylindrical wave expansions. The Lorentz reciprocity theorem is then used to solve for the field radiated by the antenna from the probe output voltage. It is shown rigorously that the antenna pattern can be determined independently of the characteristics of the measurement probe provided that certain calibration data are known. A method for determining these data from the measured far field radiated by the probe is described. It is shown that the necessary numerical integration can be performed with the fast Fourier transform algorithm. Experimental results are presented to validate the theory and to demonstrate its practicality from a measurement and computational viewpoint. 相似文献
20.
J. A. MORENTE R. P. TORRES A. SALINAS J. PORTI 《International Journal of Electronics》2013,100(3):623-635
An analysis is described to calculate the optimum load which maximizes the radiated electromagnetic field from a linear dipole antenna fed by a very short pulse. For each frequency in the band, the analysis is carried out by solving Pocklington's equation via a Galerkin moment method, together with a variational technique. A constraint on the energy of the radiated signal is used as an isoperimetric condition, so that the solution is physically realizable. The optimum solution is also compared with the response of an unloaded antenna. 相似文献