Research On Modulating And Encoding Of Free Space Ultraviolet Speech Communication System

Ultraviolet Optics Speech Communication is a new type communication system in free space optics communication fields. Its excellent performances such as safety,anti-interference, Non Line-of-Sight, make it different from infrared optics communication. Hence, ultraviolet optics communication gratifies the need of special and confidential communication in army.Firstly, according to analysis of ultraviolet optics transfers characteristics, we choose ultraviolet optics whose wavelength is 256nm as the carrier of free space optics communication. Because of aerosphere, the astrospace ultraviolet optics whose wavelength is less than 290nm is absorded before it reaches the earth's surface. There is no any disturbance which comes from the nature. Furthermore, ultraviolet optics can realize non line-of-sight communication in certain area because of its dispersion. That is much different from the rigorous orientation's restrictions of transmitter and receiver in the infrared optics and laser communication which is only used in line-of-sight communication. This is a very fascinating characteristic of ultraviolet optics communication.Secondly, according to particularity and the real conditions, analysed and compared several modulating methods, ultimately we choose the ultraviolet lamp and one adaptive modulating method. Because of the restrictions in the choice of ultraviolet optics lamp, our ultraviolet optics communication system adopts special ultraviolet optics modulating method. For the 256nm-ultraviolet-optics, either ultraviolet laser or ultraviolet led has some disadvantages which make them not be used in ultraviolet optics communication. The system choose the ultraviolet gas discharge lamp as lamp-source, Then the modulating method is decided, this is significant for the hardware design of the whole system.Thirdly, considering transfers velocity of ultraviolet optics communication system, we design a speech encoding method in order to realize speech communication through the ultraviolet optics. Using C6711DSK of TI as the speech encoding plantform, the relationship of host p87c51, AMBE2000 and off-chip TLC320AD535 is given. The purpose of the design is to utilize the current technology and condition that we hold to do some elementary research on ultraviolet optics speech communication used in army. For three years hard research works, we accumulate some experiences in modulating of ultraviolet optics and speech encoding. We complete the ultraviolet optics communication in low velocity. The results of experiment indicate our design is feasible and worthy of further research.