共查询到19条相似文献,搜索用时 156 毫秒
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副瓣电平是天线的重要技术指标之一,较低的副瓣电平可以减弱杂波影响、提高雷达的抗干扰能力。但在实际设计天线的过程中,不可避免的会引入随机误差,使得阵列的口径分布发生变化,直接影响天线阵的性能。随机误差的引入最终都可以表现为阵列各个单元的幅度误差和相位误差,故需要分析随机幅相误差对阵列天线副瓣电平的影响。本文以此出发,应用统计学理论,得到计入随机幅相误差后阵列副瓣区副瓣电平的统计特性,并由此分析在整个副瓣区域内最高副瓣电平的统计特性。结合计算机仿真,证明分析计算结果的正确性。 相似文献
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文中针对数字波束形成系统,推导出阵列天线的通道幅相误差和阵元位置误差对波束方向图的第一副瓣、零陷深度及半功率波束宽度影响的一般规律。并且对数学公式进行了详细的推导。分析与仿真结果表明:随机误差对波束方向图性能的影响主要与天线阵列的权系数和阵元数目有关。 相似文献
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对误差分布函数进行了理论分析,通过分析有源相控阵系统的组成,构建了其误差组成结构,并推导了误差计算公式.通过理论推导和仿真分析研究了幅相误差对有源相控阵天线副瓣电平的影响.结合误差计算公式和副瓣电平公式得到了实现所需副瓣电平的幅相误差分配方法. 相似文献
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超低副瓣阵列天线的公差分析 总被引:10,自引:1,他引:9
对S波段超低副瓣阵列天线中的线阵和面阵的相关误差,非相关误差与平均误差与副辨电平,最大误差副辨电平之间的各种关系进行了分析,得到了一些有用的公式和图表。实验证明水平面在300GHz内最大副瓣电平低于-40dB,宽角副民平低于-50dB,垂直面内在中心频率处最大副瓣低于-38.7dB,交叉极化最大副民平低于-40dB。 相似文献
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研究随机误差对电扫阵列天线(包括频扫和相扫天线)方向性和副瓣电平的影响,根据频扫阵列天线实际存在的随机误差给出了计算结果。 相似文献
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In this paper, approximate formulas are derived for the electromagnetic pulse due to a delta-function current in a horizontal electric dipole on the planar boundary between a homogeneous isotropic medium and one-dimensionally anisotropic medium. The components of the electric field consist of two delta-function lateral pulses which decrease with the amplitude factor /spl rho//sup -2/ and travel along the boundary with different velocities and different amplitudes. Also, it is noted that the formulas for the time-dependent magnetic field components obtained by Fourier transforms from the approximate formulas in the frequency domain are not adequate. 相似文献
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Error performance of selection combining and switched combining systems in Rayleigh fading channels with imperfect channel estimation 总被引:3,自引:0,他引:3
Lei Xiao Xiaodai Dong 《Vehicular Technology, IEEE Transactions on》2005,54(6):2054-2065
In this paper, we present a general analysis of the performance of selection combining (SC), switch-and-stay combining (SSC), and switch-and-examine combining (SEC) systems in Rayleigh fading channels with imperfect channel estimation (ICE). The complex channel estimate and the actual fading are modeled as jointly Gaussian random variables. For SC systems with channel estimation error, closed-form expressions are obtained for the error rates of M/sub s/-ary pulse amplitude modulation (PAM) and rectangular-quadrature amplitude modulation (QAM), and simple single integral formulas with finite integration limits are derived for the symbol error probability of arbitrary two-dimensional (2-D) modulation formats. These error probability expressions are then applied to three types of channel estimation errors potentially encountered in practical systems to study their impact on the performance of selection diversity. Moreover, single integral formulas with finite integration limits are derived for the performance of SSC and SEC systems with minimum mean square error (MMSE) channel estimation. Optimum switching thresholds for 2-D modulation formats with MMSE based switched combining are acquired through numerical computation. 相似文献
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In this paper, we address the issue of imperfect channel estimation in coded systems on fading channels. Since performance of channel codes is influenced in different ways by different components of channel-estimation errors, we develop a simplified model which separates the estimation errors of a Wiener-filtered received signal into the amplitude error and the phase error. Based on the model, we derive tight bounds on component error variances. Moreover, we prove that the classical Wiener filter results in a biased estimate of the channel amplitude. We also show that the probability of having a phase-estimation error large enough to cause decision errors in the receiver is significant. Using our model, we derive an approximate upper limit on the optimum pilot-symbol spacing and approximate lower limit on bit-error rate performance of coded systems with a given pilot-symbol separation. The proposed model and derivations are confirmed by extensive simulations. 相似文献
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An-Hui Liang Wei-Bin Huang Chong-Cheng Fan 《Lightwave Technology, Journal of》1989,7(12):2046-2051
Two moment-related definitions for the mode-field half-width (MFHW) of a planar optical waveguide with an arbitrary index profile are proposed, and their relationships to the MFHW based on a Gaussian least-mean-square fit are derived. Various formulas for calculating splice loss for two identical planar waveguides under transverse offset and axial tilt are presented, including accurate formulas based on transmission coefficient, approximate formulas based on various MFHW definitions, and error formulas for using them both. Numerical data for symmetrical step-index slab waveguides show that for small misalignments, splice losses calculated from moment MFHWs are more accurate than those from the Gaussian MFHW, and error formulas can be used to obtain conservative estimates 相似文献
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Some simple, approximate formulas are provided for calculating the axial ratio of a circularly polarized (CP) wave, as generated by two radiating elements that have amplitude, phase, orthogonality, and polarization errors. The derivations of the formulas are not presented, but agreement between the exact and approximate results is demonstrated for a set of sample cases, assuming that the above errors are small 相似文献
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《Microwave Theory and Techniques》1981,29(2):135-142
A numerically efficient and accurate method for the derivation of line capacitance and characteristic impedance of a thin microstrip line is discussed. Galerkin's method is found to give highly accurate results when only one or two basis functions are used. We use three methods to derive approximate formulas for microstrip line capacitance and characteristic impedance. Asymptotic lower bounds derived through the variational method and matched asymptotic expansion methods give expressions which reveal the functional forms of these approximate formulas. Seminumerical approximation gives rise to formulas usable on a desk calculator. It is found that there is excellent agreement between the seminumerical formulas, the asymptotic formula derived through matched asymptotic expansions and numerically derived results. 相似文献