Research On Modulating Of Solar Blind Ultraviolet Speech Communication

Ultraviolet Speech Communication is a new kind of communication technique in free space optics communication fields. Some excellent performances such as safety, anti-interferencethesis, Non Line-of-Sight, make it different from other communication model. Hence, ultraviolet communication can be applied in some special occasions to make up for the shortage of traditional communication models .Firstly, ultraviolet light transmtting performance in atmosphere is analysed, and the single scattering model is proposed based on the ellipse - spherical coordinate system.When the solar ultraviolet radiation passes through atmosphere, the 200～300nm ultraviolet band is absorbed by the ozonosphere so strongly that it can not reach the earth's surface. So it is called solar blind ultraviolet light. In practice, the 253.7nm ultraviolet light is selected as the free space optics communication carrier. Besides, ultraviolet light is suitable for Non Line- of -Sight communication for its high level scattering performance which is another advantage compared to other models.Secondly, according to the ultraviolet light characteristics, some important devices are discussed and selected. For some superiorities such as high transforming efficiency, wide range power, excellent spectral line performance, the low voltage mercury lamp is used. To make the right modulation scheme, the low voltage mercury lamp's lighting principle and V-I charactericstics are discussed, and also considering the baseband signal is a binary style, the 2FSK-modulation modle is selected finally.Thirdly, based on the light source V-I charactericstics and modulation style selected, the whole communication framework is built. Working principle, implementation of power driver circuit, exception handling circuit, microcontroller circuit and power factor correction circuit are discussed.Last, considering the low transmission speed of the communication system, in order to relize speech communication, we raise a speech coding method. Implimentation of this method on PC is introduced.The purpose of the design is to utilize the current technology to do some elementary research on ultraviolet light speech communication. For three years hard research works, we accumulated some experiences in modulating of ultraviolet light and low speed speech encoding. In present, the system can transmit character information at the rate of 9.6Kbps with a low bit error rate. Real time ultraviolet speech communication is realized based on PC. In the end, conclusions of experiments and suggestion of improvement are discussed.