Research And Implementation Of Synchronization Technology For Short Burst Direct Spread Communication System

The short burst direct spread communication system combines the advantages of short burst communication technology and Direct Sequence Spread Spectrum(DSSS)technology.It has strong concealment,flexibility and anti-interference performance,and can combine different Digital modulation technology(such as Binary Phase Shift keying).It has been rapidly developed in the fields of military communications,satellite communications and high-speed mobile communications.Synchronization technology is the prerequisite and research focus for the normal operation of short-burst DSSS communication systems.Based on the analysis of the commonly used acquisition methods in direct-spread communication systems,this paper proposes a method of pseudo-code acquisition by using LFM pilot signals for the problem that the acquisition performance of truncated Gold codes needs to be improved,and the acquisition performance of this method is simulated.Compared with the capture method that directly uses the truncated Gold code,it shows that the proposed method has a higher capture probability under the same false alarm probability.Later,in view of the poor confidentiality of LFM signals and the inability to apply to multiple addresses,a method of using CPM orthogonal signal sets to replace LFM signals to achieve signal capture is proposed,and genetic algorithms are used to find the optimal signal set that meets the requirements of related characteristics.Finally,The capture performance of the obtained optimal CPM signal set is simulated,and the comparison with the previous two methods shows the effectiveness of the method.Aiming at the problem that it is difficult for short burst systems to use closed loops for carrier tracking and pseudo code tracking,a long signal composition method based on signal cycle backtracking is proposed,and corresponding synchronization loops are designed,including frequency-locked loop,phase-locked loop and Code ring.After that,the proposed method and the design loop are simulated,and the simulation results show that the designed loop can work normally under the short burst direct spread communication system.Using the proposed method of using the CPM pilot signal to achieve capture and the synchronization loop based on backtracking,the short-burst direct-spread communication system is designed and implemented on the FPGA hardware platform.