Research And Implementation On Line Of Sight Ultraviolet Light Speech Communication System

Ultraviolet communication is a new mode of communication,which is mostly used in extreme military operations.The existence of the blind zone of ultraviolet makes the advantages of high confidentiality,anti-interference and anti-interception capability.Ultraviolet communication uses ultraviolet light as the carrier to transmit the text,voice image,video and other signals,in which speech communication is the most basic and important mode of communication.The speech carried on ultraviolet light,can greatly exert the advantages of the contract of ultraviolet communication anti-jamming,without track laying,apply to the extreme operational environment,to achieve instant communication,secure communications has great realistic significance.Therefore,the ultraviolet speech communication system is the hotspot and main development direction of future voice communication.First of all,this paper summarized the characteristics and application of ultraviolet light communication and the research progress and status of ultraviolet communication at home and abroad.Analysed the effect of UV light transmission in the process of atmospheric absorption,scattering and turbulence,emphatically studied the LOS transmission model of ultraviolet light communication,introduced the theory of speech coding and decoding,and summarized the technical classification and performance evaluation method of low bit rate speech coding.Secondly,the overall design of ultraviolet communication system is carried out,and the system key devices and implement tools are compared and selected.In this paper,2.4 kbps MELP is studied,and the improved MELP encoding and decoding algorithm is designed to form a super frame sound code device,carried out the design of SOPC architecture and software algorithm,and the top design and function simulation and online debugging of the main algorithm module.Contrast within five kinds of modulation algorithm,the advantages and disadvantages of chose 2FSK demodulation method,for the result of the switching frequency transition zone are studied to improve problem,design the 2FSK modulation demodulation scheme,and realized the simulation of the top design and FPGA implementation.Finally,the device connection and performance test are carried out for the key components of the system.Build the audio playback and spectrum display system based on WM8731,design the top-level and sum up the speech signal processing of speech system,finish online debugging of the whole process speech signal;Build the UV LOS speech system,elaborated the system data processing procedure in detail,and the coding input signal modulation and demodulation output signal measured,found that the signal waveform is stable,and simulated the speech spectrum of original speech,2.4kbps MELP coding speech and improved coding speech,and evaluated the three kinds of speech by MOS score,the results show that the improved coding speech after UV transmission MOS points to 2.8 points,meet the tactical communications standards.