Synchronization Research, Spreading Pseudo-code Instructions In The Communication System

With the advantages of its strong anti-interference.good for hiding and the capability of multiple access.the spread-spectrum technology are more widely used in military and civilian communications systems.With spread-spectrum technology continuing to evolve.it will provide more secure communications for air defense missile system.According to the command guidance technology which is widely used in the third-generation surface-to-air missile weapons systems,this thesis used the detector of radio-controlled missile in a pre-research type of the Surface to Air Missile Weapon System as research background,and studied the pattern of the spreading code and its synchronization algorithm in the directive spread-spectrum communications in high dynamic environment.Firstly,introduced the basic principles of the spread-spectrum communications,and studyed the characteristics of the binary shift register sequences for the spread spectrum systems, selecting the balanced Gold sequences as the spreading code of the downlink data of the surface-to-air missile communications system.Then,studied the PN acquisition algorithm and analyzed the performance of the single dwell time and the dwell time time of the PN code capture,including the Synchronization time,the probability of detection and the probability of false alarm and so on, And put forward an algorithm with PN code capture of matching filters based on FFT.With modeling and simulation in MATLAB/SIMULINK,which can implement the PN capture in a code period rapidly and complete two-dimensional search of code phase and Doppler shift in case of the presence of Doppler frequency offset.Finally,analysed the phase-locked loop with the envelope-related non-coherent delay,which is commonly used in the spread-spectrum communications,and launched a theoretical analysis for the performance about the phase detector and the loop filter of the tracking loop,completing the simulation and analysis of the performance of the loop with the loop parameters changing.