The Research And Suppression Of Noise In Ultraviolet Communication System

The ultraviolet (UV) communication transmits data by UV light (wavelength200nm-280nm), which can be scattered by atmospheric particles. It has advantages of low interception rate and strong anti-interference capability, supporting all-whether work and non-line-of-sight (NLOS) communication. Recently it has become the research hotspot of more and more research institutes. The thesis mainly analyzes the impact of noise in the UV communication system, and studies methods of suppressing noiseThe first chapter makes a brief introduction of present research and developments of the UV communication at home and abroad, and gives the contents of the thesis.The second chapter introduces our UV communication platform, including transmission channel model, modulation and demodulation methods and the photoelectric devices used in the system.Chapter3analyzes noise in the UV communications system, and points out that noise mainly consists of photomultiplier tube (PMT) dark current noise, the Printed Circuit Board (PCB) noise and the background noise. A module is designed to sample the three kinds of noise. Then, this chapter analyzes their characters in time and frequency domains and the impact on the system performance.Based on the results of noise analysis, the fourth chapter proposes digital filter to suppress noise, which can overcome the disadvantages of the analog filter. FIR low-pass and high-pass digital filter are designed with FPGA to handle different conditions. Then, their effects are analyzed on suppressing noise and improving signal to noise ratio (SNR). Our experimental results also show that they can improve the performance of the communication system.The last chapter summarizes the research work that I finished, and gives some suggestions for future study.