Research On Modulation And Demodulation Technology Of Wireless Ultraviolet Communication

Wireless ultraviolet?UV?communication is the transmission of information through the scattering of UV photons and gas molecules and particles in the channel.It has the advantages of high confidentiality,low background noise,strong anti-interference ability and full-environment work.At the same time,it can carry out non-line-of-sight?NLOS?communication.It has a good application prospect in the military field and complex environmental conditions.With appropriate modulation and demodulation technology,the reliability of system can be significantly improved,and the communication rate,bandwidth efficiency and other performance of the wireless UV communication system can be significantly improved.And the overall bit error rate can be reduced.Therefore,research on modulation and demodulation technology in wireless UV communication is of great significance.Aiming at the modulation and demodulation technology of wireless UV communication system,the following several works are carried out:1.The theory and characteristics of UV communication are analyzed,and the influence of atmosphere on wireless UV communication is studied.The line-of-sight?LOS?and NLOS link models in UV communication are introduced.The effects of atmospheric absorption and scattering effects on UV communication are analyzed.The specific absorption and scattering coefficients are obtained through outdoor experimental.Compared with the simulation,the effects of absorption and scattering effects on UV communication in different weathers are analyzed in detail.2.The different modulation and demodulation techniques in wireless UV communication are studied.The specific modulation and demodulation principles and coding structures of different modulation and demodulation techniques are given.The overall performance,advantages and disadvantages of each modulation technique are summarized and analyzed.3.A new modulation and demodulation method,fixed length dual-pulse symmetric pulse interval modulation?FDPSPIM?,is proposed,and the modulation and demodulation simulation of the new method is realized.The symbol structure and modulation and demodulation principle of the new method are elaborated in detail.The design of the modulation and demodulation terminal is completed,and the simulation of the new method is realized.The average symbol length,bandwidth requirement and utilization rate,average transmission power,transmission capacity and error performance of the new mode and other modulation methods in wireless ultraviolet communication are analyzed.The performance formulas are deduced and summarized.At the same time,the numerical simulation and performance comparison analysis are compared with the six modulation and demodulation methods analyzed,and the advantages and disadvantages of the new modulation and demodulation method are summarized.Compared with PPM,FDPIM and FFDIM,the new method has obvious advantages in average symbol length,bandwidth requirement and transmission capacity.Compared with DAFDPIM,the new modulation method has better average transmit power and error performance.4.The outdoor wireless UV communication experimental device was successfully built,and outdoor experiments were carried out based on OOK modulation.Through the selection of UV light source,UV detector and filter,and adopting OPA2613 as the core of light source driving circuit,the construction of outdoor wireless UV communication experimental platform is finally realized.Through outdoor experiments under different conditions,it can be seen that the communication distance is within 45 meters or the transmission and reception elevation angle is below 20 degrees,the overall bit error rate is less than 10^-3,and the communication quality of the system is relatively good.There are 45 figures,9 tables and 68 references in this thesis.