应用双正交极化天线的MIMO卫星-地面宽带协作通信技术研究

By integration of satellite communication and terrestrial mobile communication, the Satellite-Terrestrial Broadband Cooperative Communication technology can solve the communication interrupt problem due to war or natural disasters, and can also cope with the blind areas of satellite communication indoor or in tunnels. Application of Multiple Input and Multiple Output (MIMO) technology can increase the system capacity and is able to confront with the frequency selective fading. However, the channel independence among the multiple antennas is seriously affected by the following factors and set the limitation for application of MIMO technology in the system. Firstly, the terminal volume of satellite and terrestrial mobile terminal are limited. The spaces between the antennas are small and serious coupling among the multiple antennas always happens. Secondly, the complex channel condition of satellite and terrestrial communication prevents implementation of the transmission techniques from increasing the channel independence. Thirdly, existence of high power line of sight (LOS) in Satellite communication can prevent the signal separation among the multiple antennas. This project will solve the problems above by adopting Dual-orthogonal Polarized Antennas combining with the space-time block code and constellation rotation. Then, the MIMO Satellite-Terrestrial Broadband Cooperative Communication simulation system can be built up. By consideration of the effects of the Dual-orthogonal Polarized Antennas technology on channel polarization characteristics and antennas channel correlation, and according to the operation modes of relay node, the MIMO Satellite-Terrestrial Broadband Cooperative Communication channel probability statistic model will be built up. Based on the channel model, the effects of the Dual-orthgonal Polarized Antennas technology on system performance will be analyzed, which can provide a theoretical foundation for system realization.

卫星-地面协作通信技术将卫星与地面移动通信相结合,能够解决战争、自然灾害情势下地面通信中断或室内、隧道等卫星通信盲区问题。在协作通信系统中应用多输入多输出（MIMO）技术能大幅提高系统容量并能对抗频率选择性衰落，但以下问题严重影响多天线间信道独立性，限制了该系统中MIMO技术的应用：卫星和地面移动终端体积受限、无法保证足够的天线间距，多天线间耦合严重；卫星与地面信道环境复杂，难以使用发端技术增强天线间信道独立性；卫星通信存在较强直射信号，影响多接收天线间信号分离。项目拟采用融合空时分组编码和星座旋转的双正交极化天线技术解决以上问题,仿真建立MIMO卫星-地面宽带协作通信系统模型；考查该多天线技术对信道极化特征和天线间信道相关性的影响，并依据不同中继节点工作模式，建立MIMO卫星-地面宽带协作通信信道模型；在此基础上，分析应用双正交极化天线技术的协作通信系统性能，为该系统的实现提供理论依据。

卫星与地面移动通信相结合,能够解决战争、自然灾害情势下地面通信中断或室内、隧道等卫星通信盲区问题。在卫星通信系统中应用多输入多输出（MIMO）技术能大幅提高系统容量并能对抗频率选择性衰落。项目采用融合空时分组编码和星座旋转的双正交极化天线技术解决以上问题,仿真建立了双极化MIMO卫星宽带通信系统模型，考查了该多天线技术对信道极化特征和天线间信道相关性的影响；在此基础上，分析应用双正交极化天线技术的协作通信系统性能，为该系统的实现提供理论依据。此外，本项目还利用FPGA进行了OFDM系统的数字信号处理与收发信机实现，并研究大气层对太赫兹信号吸收作用，以及研究室内环境下的太赫兹信号反射与散射作用等方面。项目研究结论表明，可利用宽带特性和双正交极化天线结构特性建立卫星通信信道模型。建模的步骤是基于4状态Markov链和经典的Loo模型。双正交极化天线对信道模型的影响参数在不同环境中几乎是一样的，这说明环境对双正交极化天线的影响是有限的。太赫兹在大气中传输，影响传输衰减的因素主要有水、氧气、二氧化碳等分子的吸收作用，导致太赫兹波的损耗严重，从而将传输路径限制在很短的距离，同时，衰减特性随着高度的增加也会发生变化。随着高度增大，大气中水汽分子数、密度会随之减小，所以造成了衰减系数也随高度增加而减小。倾斜路径传输时，太赫兹大气传输衰减随传输距离变化，距离越大，衰减越大，水平路径也是如此。随着垂直距离变大，每层的传输距离也随之变大，同时，随着仰角增大，每层的传输距离也随之变大，从而使得衰减值也随之变大。项目取得了较好的研究成果，并发表3篇SCI期刊论文，2篇EI期刊论文，授权2项发明专利。