Research Of Demodulation Technologies In Ultraviolet Communication System

As a new communication means, UV communication has some special characteristics of flexibility, low wiretapping, Omni bearing and non line-of-sight communication that are its unique advantages compared with other conventional communication. So it can meet the needs of secure communication between warships and airplane formation. In addition, the ultraviolet rays mainly transmit by scattering way and the transmission distance is limited, which determines the ultraviolet communications system has the non-line of sight communication characteristic in the limited scope. Now, UV communication is still a new research direction in many countries, whose research is general exploration and development stages. Modulation-demodulation of the UV is still a difficulty. Meanwhile, it is difficult to improve the speed of transmission for UV communication system, which can't meet the speech transmission speed.In order to solve the above problems, the paper researches on the key technologies in ultraviolet communication system. The primary research tasks is,①Analyzing the characteristics of various ultraviolet lights and selecting the UV gas discharge lamp as the system source by considering the light modulation system, the cost and developing cycle and so on.②Researching the performance and characteristics of the photomultiplier tube and selecting it as the UV signals collecting device. In addition, the installation of UV filter improves the UV-band accuracy.③Designing the signals preprocessing circuit and demodulating the signals. The original digital signal can be demodulated.④Researching the development and the characteristics of the FPGA technology, designing the demodulation circuits based on the FPGA, which greatly improve the system transmission speed.Through indoor tests, by using the demodulation circuits based on FPGA, when the transmission rate is 9.6 Kbit/s, the bit error is only 0.001%. Hence, it has laid a good foundation for further research on the solar blind UV communication system and reaching the transmission speed about the real-time speech communication.