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"信号与系统"课程是电类专业的重要主干课程,在学习掌握信号与系统分析基本原理与方法的基础上如何做到学以致用,以提高学生的学习兴趣与实践能力,应该是任课老师必须思考的一个问题.本文基于信号与系统的基本理论与分析方法对OFDM信号传输过程进行了分析与探讨,以使学过信号与系统及通信原理课程的同学也能理解与掌握OFDM信号的传输原理与结构特点.应用Matlab仿真环境建立了OFDM传输方案的仿真平台,通过实验,提高学生的分析能力、理解问题能力及实践动手能力. 相似文献
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建立一种基于双平行相位调制器的OFDM-ROF实验仿真系统.在中心站采用双平行相位调制器产生双边带光载毫米波,利用光交错复用器将信号进行上边带和下边带分离,将OFDM信号通过马赫曾德尔调制器调制到一个边带上进行传输.OFDM的调制和解调部分使用MATLAB软件编写,OFDM-ROF系统实验仿真平台基于软件Optisystem进行搭建,并给出了光载OFDM信号的产生模型和系统仿真结果.实验表明,OFDM-ROF系统经过色散补偿后大幅度提高了系统的传输距离. 相似文献
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随着第五代移动通信技术、低轨卫星互联网等通信系统的发展,正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术凭借良好的频谱效率得到日益广泛的应用。但OFDM系统信号参数复杂,对非合作条件下的盲信号分析带来了较大困难,需要在尽可能少的先验信息下,判定信号参数。为此,提出了一种基于相位轨迹特征的OFDM信号盲分析方法,利用OFDM信号固有的循环周期性,粗估计子载波数及子载波间隔,在此基础上通过非线性变换等处理获取子载波间及符号间的相位变化轨迹,基于相位变化轨迹分析其反映的采样定时误差、载波频率偏差等参数信息并修正估计值,最终通过信号接收误码率进行估计参数正确性验证,实现了对OFDM信号盲分析。仿真分析结果表明,在信噪比(SNR)大于8 dB时,即可实现参数准确估计,优于利用先验信息的相关处理方法。 相似文献
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Pilot-symbol aided coherent M-ary PSK modems in digital cellular mobile radio systems are analyzed theoretically. The error-floors caused by the Doppler spread in a fast fading channel are removed in both flat and selective fading channels. However, the error-floors caused by the delay spread are lower-bounded by those that exist in the ideal coherent detection. The systems are modeled as frequency-selective fast Rayleigh fading channels, corrupted by co-channel interference (CCI) and additive white Gaussian noise (AWGN). In the proposed scheme, pilot symbols are inserted periodically to monitor the channel characteristics. The fading processes experienced by the pilot symbols are used to estimate those suffered by the data symbols using interpolation or filtering. The estimated fade characteristics are used to compensate the random phase variation caused by the Doppler spread, so that the signals can be demodulated coherently. The theoretical performances of the fade compensated coherent modems are evaluated. The results show that the fade compensated coherent demodulation with the least redundancy achieves the same performance as the ideal differential detection in a fading channel. The performance approaches that of the ideal coherent demodulation as more redundancy is allowed. The pilot-symbol-insertion (PSI) scheme is also applicable to M-ary QAM modems and Rician channels. The residual frequency offset can also be compensated by the PSI technique 相似文献
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文章用金相显微镜观察、统计了InSb晶片扩散前、后,经择优腐蚀后呈碟形坑的表面
微缺陷。结果显示这类缺陷的一部分是InSb晶体原生缺陷,一部分由扩散诱生。分析后认为由扩散诱生这类缺陷的原因主要为晶片表面粘污,已证实清洗更洁净的晶片,能有效抑制扩散过程中诱生的这类缺陷。 相似文献
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本文应用混合技术分析了在TE平面波激励下,理想导体半圆柱的双站散射。该混合技术是把半圆柱劈附近的电流表示为未知数,圆柱曲面上的一阶电流应用Fock理论求解,高阶绕射电流表示为含有未知系数的Fock型函数。圆柱平面上的一阶电流用物理光学近似和曲劈的一致性几何绕射理论得到。劈的二阶绕射电流表示为含有未知系数的GTD形式。然后通过磁场积分方程,运用简单矩量法求得劈附近的电流和未知的绕射系数。最后计算了理想导体半圆柱的双站散射截面,结果与矩量法的结果吻合得相当好。 相似文献
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Schmidt G. Sidorenko V.R. Bossert M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2009,55(7):2991-3012
Interleaved Reed-Solomon codes are applied in numerous data processing, data transmission, and data storage systems. They are generated by interleaving several codewords of ordinary Reed-Solomon codes. Usually, these codewords are decoded independently by classical algebraic decoding methods. However, by collaborative algebraic decoding approaches, such interleaved schemes allow the correction of error patterns beyond half the minimum distance, provided that the errors in the received signal occur in bursts. In this work, collaborative decoding of interleaved Reed-Solomon codes by multisequence shift-register synthesis is considered and analyzed. Based on the framework of interleaved Reed-Solomon codes, concatenated code designs are investigated, which are obtained by interleaving several Reed-Solomon codes, and concatenating them with an inner code. 相似文献
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Kh. A. Abdullin N. B. Bakranov D. V. Ismailov J. K. Kalkozova S. E. Kumekov L. V. Podrezova G. Cicero 《Semiconductors》2014,48(4):471-475
Composites formed from ZnO nanorods in combination with CuO or Ag nanoparticles are produced by the deposition of CuO or Ag nanoparticles onto ZnO nanorod arrays grown by the hydrothermal technique. The CuO nanoparticles are synthesized by the vacuum thermal deposition of a Cu layer followed by vacuum annealing at a temperature of 350°C for 1 h. CuO particles covered with a layer of nanoneedles are obtained. The current-voltage characteristics of the ZnO/CuO layers are indicative of the formation of a p-n junction. The ZnO/Ag composites are produced by the electrical deposition of Ag nanoparticles synthesized in an aqueous solution of silver nitrate and sodium citrate. The surface morphology and the optical and electrical properties of the samples are studied. 相似文献
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为了研究地震产生的机理, 需要分析和研究地基极低频(Extreme-Low Frequency, ELF)电磁波的传播特性.地基任意ELF线天线产生的电磁场可由ELF点源产生的电磁场进行叠加.通过地基ELF点源电磁场的表达式导出了ELF线天线在地-电离层壳体中电磁场的表达式.利用加速收敛算法得到了单条和两条ELF线天线产生电磁场的场强空间分布图, 用色标表示场强值在空间分布的强弱.电场水平分量的场强值要比垂直分量的场强值小, 磁场水平分量的场强值要比垂直分量的场强值大.而且两条线天线产生的场强值要比单条线天线产生的场强值大. 相似文献