【作者】 贾转红；

【导师】 敖发良；

【作者基本信息】 桂林电子科技大学 ， 电磁场与微波技术， 2007， 硕士

【摘要】 本文介绍了自由空间光通信(FSO)和射频通信(RF)的基本理论、研究现状和发展趋势。为了保证自由空间光通信的传输质量,针对大气信道的恶劣环境造成的可靠性下降问题,引入了一种减小FSO传输信号衰减的混合FSO/RF通信系统,并对该系统中两条链路的自动切换性能进行了分析研究,结果表明混合系统的可用性高于单链路。本文根据最新的ITU-R建议,深入分析大气衰减效应和大气湍流效应对信号传输的影响,尤其是云、雾、雨的散射衰减作用,初步构建混合FSO/RF通信系统信道的物理和数学模型,拟定了自由空间光通信的流程图,并依据该流程图进行性能仿真。该流程的物理意义清楚,形式简单。另外通过对大气衰减信道和湍流信道的分析仿真,模拟出两种信道光斑的差异,得出一个重要的结论:大气衰减信道适合用接收功率来描述,而大气湍流信道适合用接收光斑来描述。本文在对接收功率与误码率性能分析的基础上,推导出两个具体的链路切换门限值,提出了一种新的切换方案:利用DSP来进行判断处理,通过矩阵切换开关来实现切换功能。另外,将混合FSO/RF系统的性能与前人的实测结果比较,两者基本吻合。更多还原

【Abstract】 The basic theories, state-of-the-art and development of free space optical (FSO) and radio frequency (RF) communication are introduced in this paper. In order to ensure the transmission quality of FSO, a hybrid FSO/RF system used to decrease the attenuation of FSO transmission signals is presented for the problem of decreasing reliability owing to the severe environment of the atmospheric channel. Then the automatic switchover performance of the two links of the system is analyzed and researched, and the results show that the availability of the hybrid system is better than the single link.According to the newest recommendation of ITU-R, the effects on signal transmission caused by atmospheric attenuation and turbulence are deeply analyzed, especially clouds, fog and rain scattering. The physical and mathematical model of hybrid FSO/RF system is designed, the flow chart of FSO communication is provided and the link performance is simulated. The physics meaning of the flow chart is clear, and its format is simple. Moreover, by performance simulation of the atmospheric attenuation channel and the turbulence channel, the differences between light spots of two channels are simulated and an important conclusion is concluded that the received power is suitable for describing the atmospheric attenuation channel while the received light spots are suitable for describing the atmospheric turbulence channel.Based on the performance analysis of the received power and bit error rate (BER), two certain thresholds for link switchover are deduced and a new switchover scheme is put forward. Digital signal processor (DSP) is used for judgment and a matrix on-off is used for implementing switchover. In addition, by comparing the simulation performance with the former experimental results of hybrid FSO/RF system, the results show that they are similar with each other.更多还原