共查询到19条相似文献,搜索用时 125 毫秒
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铁氧体吸波体是保证EMC屏蔽暗室符合FCC及IEC标准低频性能要求的关键元件,文章通过理论分析,给出了铁氧体吸波体的吸波性能与其磁损耗角正切之间的数学表达式,并对用于吸波体的典型铁氧体材料进行了性能分析,在此基础上,提出了铁氧体吸波体的设计准则。 相似文献
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为提升暗室吸波工程的设计能力,运用镜像射线跟踪法对10 m 法电波暗室进行仿真设计,通过合理布置吸波材料,考虑一次反射和二次反射对静区的影响,计算了不同极化方式下静区的反射电平、归一化场地衰减和场均匀性。结果表明垂直极化和水平极化时,场地电压驻波比仿真与测试偏差小于2.3 dB;归一化场地衰减仿真与测试误差小于3 dB,场均匀性误差小于2 dB。仿真与测试结果吻合较好,各项指标均满足设计要求,验证了吸波材料布局的合理性及算法的可靠性。该仿真方法可应用于暗室静区性能评估,优化吸波材料布局,进而有效缩短设计周期。 相似文献
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用射线法预测电波暗室的性能 总被引:1,自引:0,他引:1
本文探讨了一种预测 EMC电波暗室归一化场地衰减 (NSA)的方法。此方法是按照暗室的 NSA测试过程,依据几何光学理论来计算接收天线处的场强值,并转化为 NSA的计算值。根据计算所得的 NSA值可以为暗室性能的预测提供参考。本文通过所编制的计算程序,计算了以铁氧体为吸波材料的 3米法暗室的 NSA值,并对计算结果进行了分析和讨论。此方法既适用于 3米法暗室,也适用于 10米法暗室,同时对由于空间所限而设计的不规则暗室也有一定的参考价值。 相似文献
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传统的电路模拟吸波材料设计只考虑正入射时的吸波性能,当入射角较大,尤其是大于30°时,雷达吸波器的吸波效果明显恶化。随着现代双站雷达探测技术的发展,雷达探测电磁波可能来自不同的空间方向,这就要求雷达吸波材料不仅在电磁波正入射时具有较高的吸波性能,在斜入射时同样实现良好的隐身特性。为此,该文提出了一种新型的宽带吸波材料。该材料由嵌入集总电阻的导电方环阵列和设计良好的宽角阻抗匹配(WAIM)层组成。由于WAIM层的存在,斜入射情况下的吸波性能明显改善。同时,针对电磁波正斜入射情况,该文提出了准确的等效电路模型以及严格的数学计算模型,使得结构设计清晰明了。测量结果表明,正入射时的吸波带宽达到137.1%。当入射角小于45°时,所设计吸波材料在反射系数衰减至少10 dB情况下的公共百分比吸波带宽达到110.5%。等效电路模型计算、仿真与实测结果之间的相似性验证了该文设计的有效性。 相似文献
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基于十字分形结构,设计了一种小型化、超薄、高吸波率以及无表面损耗层的超材料吸波体。该吸波体是由两层金属及其中间的有耗介质组成,上层金属是由周期性蚀刻十字分形的贴片组成的电谐振器,下层金属不蚀刻,作为整个金属地板。通过优化结构参数,吸波体单元尺寸仅为0.13λ,厚度为0.0093λ,最大吸波率达99.6%。将此吸波体加载于普通微带天线上,制备了一种新型超材料天线。仿真和实验结果表明:相比普通微带天线,新天线在5.52~5.68 GHz工作频带内,法向RCS减缩都在3 dB以上,最大减缩量达13.5 dB,单站RCS在-18°~+18°角域减缩超过3 dB,且天线辐射性能保持不变,证实了该吸波体具有良好的吸波效果,可以应用于微带天线的带内隐身。 相似文献
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Low-Frequency Model for Rectangular Semi-Anechoic Chambers 总被引:1,自引:0,他引:1
Prez I. M. Nuo L. Pereira F. D. Q. Tejedor J. V. B. 《Electromagnetic Compatibility, IEEE Transactions on》2006,48(4):725-733
An efficient and accurate method to compute the electromagnetic field inside a rectangular semi-anechoic chamber from 30 to 100 MHz is provided. A modal analysis method is used to develop the homogeneous and inhomogeneous solution. They are then combined with a generalized circuital analysis to take into account the effect of the several layers of ferrite and dielectrics on the walls. Several numerical results of the normalized site attenuation (NSA) of a semi-anechoic chamber are provided and compared with measurements, showing a very good agreement 相似文献
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Correction factors for normalized site attenuation 总被引:1,自引:0,他引:1
Sugiura A. Shinozuka T. Nishikata A. 《Electromagnetic Compatibility, IEEE Transactions on》1992,34(4):461-470
EMI standards require test sites to be validated by measuring the normalized site attenuation (NSA) instead of the classical site attenuation (CSA). Theoretical investigations are, therefore, carried out on the general formulation of NSA and CSA, where chain matrices are introduced to account for the effects of antenna circuits. It is found that the theoretical NSA values given by the standards are based on three assumptions inappropriate to measurements using tuned dipole antennas. Thus, correction is considered requisite for every NSA measurement when tuned dipoles are used. In this connection, new correction factors are proposed for various measurement configurations at 3-, 10-, and 30-m test sites. In addition, numerical evaluations are made on the correction factors applicable to the NSA measurements with antenna factors calibrated at 2 or 3 m above a metal plane 相似文献
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Wakabayashi R. Shimada K. Kawakami H. Sato G. 《Electromagnetic Compatibility, IEEE Transactions on》1999,41(2):93-99
Two types of broad-band antennas are widely used for electromagnetic interference (EMI) measurements in the frequency range from 30 to 1000 MHz. Log-periodic dipole antennas (LPDA) are mainly used for the range above 300 MHz and biconical antennas for the range less than 300 MHz. These two antennas have linear polarization. However, EMI measurements can sometimes be more conveniently made with an antenna having circular polarization and so we propose an improved LPDA, which has circular polarization. This LPDA has a second array of dipoles so arranged that each dipole of the second array has a quarter-wavelength phase difference from that of the corresponding dipole of the standard LBDA array for the given radiation field. For this reason, we named it a cross-element LPDA. The cross-element LPDA does not need a broadband 90° hybrid junction to produce circular polarization. We calculated the height pattern and the frequency characteristics of the classical site attenuation (CSA) for the cross-element LPDA when used for both transmitting and receiving, as well as the antenna factor. Moreover, we calculated the normalized site attenuation (NSA) when the cross-element LPDA is used for receiving or for both transmitting and receiving 相似文献
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介绍电磁兼容测试场地归一化场地衰减(NSA)理论值计算的方法,此方法可用于不同测试条件下(不同的测试距离,收、发天线不同的高度等)NSA理论值的计算. 相似文献
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NSA理论值的计算方法 总被引:2,自引:0,他引:2
介绍了电磁兼容测试场地归一化场地衰减理论值的计算方法,可用于不同测试条件下NSA理论值的计算。计算结果与CISPR出版物16-1中给出的标准值之差不大于0.1dB。 相似文献
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General formulas for normalized site attenuation (NSA) are derived in terms of antenna impedances by using the two-port circuit theory to show the effects of mutual coupling. The investigations focus on the antenna factors and antenna calibration procedures that are appropriate for NSA, and the validity of the NSA concept is discussed on the basis of these theoretical investigations. The NSA measurements are found to be appropriate for site validation when using broadband antennas having constant antenna factors. It is theoretically concluded, however, that the original concept of the NSA may not be applicable to the use of tuned dipole antennas, even after adopting the correction factors specified in the existing ANSI standard. NSA is shown to require different correction factors if the antennas have changeable antenna factors 相似文献