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1、上海交通大学 硕士学位论文 基于全波分析的MIMO无线传输模型 姓名：练成栋 申请学位级别：硕士 专业：电磁场与微波技术 指导教师：金荣洪 20080101 上海交通大学硕士学位论文 II 含具体收发天线和空间信道在内的更为可靠的 MIMO 系统分析方法是 很有必要的。 本文运用电磁场基本理论结合全波分析方法分析 MIMO 无线传输 模型的特性，重点分析了 MIMO 系统中收发天线的特性以及它们对于 MIMO 系统的影响。本文提出使用收发天线上的电流分布作为 MIMO 系 统收发信号的表征方式，其原因是由于电流分布不仅包含幅度、相位 和空间分布信息， 而且是收发天线具体特性和天线阵列互耦等一系
2、列 信道信息影响的综合结果， 在理论上甚至可以由天线电流分布得到整 个空域的场分布， 故而采用电流分布作为分析对象实质上包含了更为 丰富和完整的系统信息。 为了能够精确得到收发天线上的电流分布， 本文通过建立完整和 详细的收发系统模型， 采用电磁场全波分析方法编程计算得到特定环 境下天线电流分布的精确解。 故本文首先使用不同方法求解天线阵列 的电流分布， 以此证明了该方法的正确性并且说明针对不同问题选用 不同的数值计算方法以减少计算时间并提高计算精度。 其次本文从电流分布的角度详细研究了 MIMO 系统收发端天线阵 列间的互耦效应和MIMO信道的空间相关性等影响MIMO系统性能的基 本因素。M
3、ATLAB 仿真结果表明，天线间的互耦效应使得天线阵列单 元上的电流分布围绕不计互耦下的电流分布波动， 其波动的特性类似 于贝塞尔函数特性，与现有的理论分析结果和测量结果十分吻合，这 也从电磁角度揭示了天线互耦效应对 MIMO 系统影响的原因。此外， 仿真结果还证明了从电流分布角度定义 MIMO 信道空间相关系数方法 的准确性和有效性， 并且在计算过程中本文首次提出以来波角谱能量 比为原则确定理论分析模型的参数， 并且证明了用该方法建立的模型 能够适用于多种来波角谱分布的情况， 这也为在不规则来波角谱或者 具有多个主方向的来波角谱分布环境提供了一种有效的分析方法。 上海交通大学硕士学位论文 I
4、II 最后，本文对前面的研究做了简要总结，并且对从电磁场谱域角 度定义 MIMO 空间相关性作了一定的仿真与理论探讨， 拓展了 MIMO 系 统的研究思路，也指明了自己今后的研究方向。 关键词：关键词：多输入多输出（MIMO） ；全波分析；天线；电流分布 上海交通大学硕士学位论文 IV MIMO WIRELESS COMMUNICATION MODEL BASED ON EM FULL WAVE METHOD ABSTRACT With the high-speed development of modern communication technology, wireless communi
5、cation technique for excellent performance and high capacity is coming to peoples great attention in related fields. The wireless resources, especially the frequency resources, have become more and more precious. Many efforts have been taken for improve the utilization of these resources more effici
6、ently in B3G / 4G. Researches have indicated that multiple-input multiple-output (MIMO) systems using multi-element antenna arrays (MEA) at both the transmitter and receiver can provide substantially higher data rates and better spectral efficiency than the traditional systems in rich multi-path env
7、ironments. Therefore, MIMO has considered the key technology in the futures wireless communication systems. However, there are still several limitations in traditional methods of the study on MIMO systems. One of them is that in nowadays study, the antennas on both sides are always considered as omn
8、i-directional only for the simplicity, which neglects the effect between antennas and MIMO signals. It must also be noted that in conventional methods, the expression of the channel impulse response is just based on the assumption of point-to-point transmission using ray-tracing simulations, which n
9、eglects the spatial distribution of signals. Furthermore, the ray-tracing method is on the basis of the assumption that the dimension of 上海交通大学硕士学位论文 V the scatterers is far larger than the wavelength of the incoming signals, which is difficult to be satisfied in many kinds of situations, especially
10、 in the indoor environment. As a result, there is still difference between the theoretical results and the measurements. This has caused many research efforts for presentation of new models to decrease this difference. According to the existing problems in the traditional MIMO researches, it is nece
11、ssary to find out a more dependable analytical model for the MIMO study, which includes both the transmitting and receiving antennas and the space channel. In this thesis, the theory of electromagnetic field and the full wave methods are used to analyze the characteristics of MIMO wireless communica
12、tion model. We especially study the characteristics of the transmitting and receiving antennas and their effect on the performance of MIMO systems. The current distributions on antennas are used for the evaluation for the reason that the current distributions contain the effect of both spatial field
13、 distributions, the form of antennas and the effect of mutual coupling, by which more channel information can be included. Furthermore, a relationship between full wave modeling and channel information is tightened directly. In order to obtain the accurate current distributions, in this thesis, the
14、specific channel model is established and the full wave methods are introduced for the calculation. First, the accuracy of this method is demonstrated by choosing different kinds of calculation conditions and the most applicable one is chosen for the use of next study. Then, we pay much effort on th
15、e study of the effect of the mutual coupling and channel correlation on the performance of MIMO systems. The simulation results by MATLAB show that the current distributions on the coupling antenna arrays fluctuate around the one on the no-coupled antennas, which agrees quite well with the measureme
16、nt results. 上海交通大学硕士学位论文 VI Furthermore, the numerical results also verify the rationality of the definition the correlation coefficient from the current distribution point of view. Additionally, it is the first time that a new parameter, the power proportion, is used to set the channel model so that this kind of model can be suitable for different kinds of PAS cases and even applicable in more complex ci
