Research Of High Data Rate Capture Quickly In Direct Spread Spectrum System

Air rescue system is the equipment for completing life-saving mission in the complex environment, which needs high confidentiality and disturbance. Since spread spectrum technology has good anti-jamming,anti-interception,anti-multipath,multiple access capability,good security and high precision, the spread spectrum system is the most appropriate means of communication. Spread spectrum communication technology is one of the most advanced radio communication technology in the today's information society, has attracted more and more attention. With the air rescue system upgrades, more and more demands appear in the feature, and image communication is needed to providing more detailed environment of the pilots to be saved for rescue workers.The main research contents of paper are as follows:1) According the characteristics of the images collected in the life-saving system and the demands for image transmission, the more mature JPEG compression algorithm is adopted to compress the color images collected.2) As the compressed images still contain significant information, the paper researches the M-ary orthogonal spread spectrum system based on the traditional direct spread spectrum system, chooses 16-ary orthogonal spread spectrum for image transmission, and designs launch and receiving system.3) While researching M-ary orthogonal spread spectrum system, the paper designs a spread orthogonal code with good correlation and orthogonality through the simulation and analysis of the correlation of pseudo-random code.4) In the process of spread spectrum image transmission system, the paper researches rapid capture technology, such as:traditional sliding correlation,matched filter method,FFT frequency domain parallel acquisition method, and analyzes their capture performance. PMF-FFT method has been more improved than the traditional capture methods in the capture time and system complexity by the research and analysis of PMF-FFT method. 5) The paper adopts zero padding method and the window functions to compensate, also compares and analyzes the two methods by locating the data and analyzing the reasons for the scallop catch losses of PMF-FFT method in the capturing process.6) The paper proposes two-way sliding correlation acquisition methods, also analyzes and simulates its performance for the shortcoming of the traditional sliding correlation which consumes longer time in the long code acquisition.