【作者】 向平；

【导师】 肖沙里；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2009， 硕士

【摘要】 日盲紫外通信是一种新型的自由空间光通信方式。由于大气层中的臭氧层对200nm到280nm之间的紫外光有强烈的吸收作用,在这个波长范围内的太阳辐射光几乎不能到达地面,即称日盲紫外光;以日盲紫外光为通信载体的通信系统将不会受白昼和夜晚环境的影响,从而大大提高了通信的抗干扰能力。该系统还具有灵活、低窃听、全方位和非视距通讯的独特优势,可满足军舰、飞机之间的保密通讯需要。首先对紫外光大气传输特性进行分析,研究了大气吸收,大气散射和大气湍流对紫外光通讯的影响。根据Luegtten等人提出的基于椭球坐标系的非直视单散射信道模型,对紫外光通讯的能量损耗做出了定量的分析。根据实验仿真结果,得出以下结论:(1)非直视紫外光通信,采用斜收发(仰角小于90o)方式,系统传输损耗最小;(2)发射光束孔径角和探测器接收视场角越大,系统传输损耗和脉冲延时将越小,越便于探测器接收。其次,根据紫外通信发射系统的调制方式和大气传输特性对紫外光接收系统的设计做了详细的描述。采用调频技术对紫外气体放电灯进行频率调制,将电信号转换为光信号,接收端紫外光信号经光电倍增管接收转化为电信号,电信号经滤波、放大和电平变换把正弦信号转化为TTL型方波信号;方波信号送FPGA,FPGA利用过零脉宽检测法对信号进行解调,还原出原始信号。由于紫外通信系统的传输速度难以提高,本系统能够实现的最高速率为9600bit/s,无法直接满足语音传输的速度要求,因而,语音的实时压缩技术也成为该系统的关键点。选用AMBE-1000语音压缩编解码芯片对语音信号进行压缩处理,可满足紫外语音通信系统的实时性要求。在此基础上,研制出了一套日盲紫外光通信系统实验样机。实验结果表明:该套系统使用灵活,性能稳定,在200m视距范围内,通信速率为9600bit/s时,能够实现实时语音通信和数据传输。为了实现更远距离和全双工通信,最后提出了系统的改进意见。更多还原

【Abstract】 Solar-blind Ultraviolet Communication is a new type communication in free space optical communication field. Atmospheric gases, particularly ozone and oxygen, are strong absorbers of light in the spectral region between 200nm to 280nm, so that the amount of solar radiation reaching the ground in this waveband is negligible. The ultraviolet in this waveband is so-called solar-blind urtraviolet. A new generation of communications using Solar-blind UV as medium will not be affected by daytime and nighttime environment, thus the communication ability of anti-jamming can be greatly improved. This device also has some unique advantages, such as flexible, all-dimentional, and non-line-of-sight communication, which can meet the needs of warships, aircraft squadron confidentiality communications.Firstly, some characteristics are discussed, such as atmospheric absorption, atmospheric scattering and atmospheric turbulence, which affect the performance of Ultraviolet Optical transmission characteristics. According to the single scattering model developed by Luegtten used in research on atmospheric channel model for NLOS ultraviolet communication, the power loss in Ultraviolet Communication can be analyzed quantitatively. The results of simulations indicate: (1) the value of transmission loss can be minimum, while both the transmitter apex angle and the receiver apex angle are less than 90o in NLOS ultraviolet communication; (2) the value of transmission loss will decrease, while the transmitter beam divergence and the receiver half-field view increase.Secondly, the design of ultraviolet receiver is described in details according to the modulation of ultraviolet transmitter and the ultraviolet characteristics. First, applying FM technology to UV gas discharge lamp, the electric signals will be converted into optical signals. Next, optical signal is received by photomultiplier tube in receiver, which is converted into electrical signals. Then, electrical signal is filtered, amplified and converted into TTL pulse signal. Finally, the original signal can be extracted by FPGA based on the principle of zero-crossing detection from the modulated signal. Besides, it is difficult to improve the data rate of UV communication system. The maximum data rate is only 9600bit/s, which can not directly meet speech transmission. Consequently, the real-time speech compression technology has become the key point of the system. In order to meet the real-time voice transmission demand of UV communication system, the speech encoding and decoding chip AMBE-1000 is selected.Base on the above research, the prototype of ultraviolet communication has been designed and realized. Experimental results indicate that this device is flexible and stable, Within the distance of 200m, the real-time speech communication and character transmission can be performed in the the transmission rate of 9600bit/s. In ordor to improve transmission distance and full-duplex communication, some good suggestions will be proposed in the end of this paper.更多还原