Research Of Pseudo-code Synchronization Technology In DSSS Based On FPGA

Spread spectrum communication(SSC)is a kind of information processing and transmission technology.In the information age,SSC technology has been used widely in military,civil,and commercial fields because of its excellent performance such as confidentiality,anti-interference and code division multiple access.With the continuous application and development of FPGA technology in the field of wireless communication system,SSC technology and FPGA technology have the opportunity to combine,and show great advantages in the wireless communication industry.Compared with the conventional narrowband communication system,the SSC system has unique advantages,but its hardware design and software design are more complex,and in order to recover the original information accurately,its implementation conditions are more stringent.In addition to the operation of the conventional communication system,the receiver also needs to use the same pseudo-random sequence for correlation processing as the transmitter spread spectrum modulation,and only when the phase of the local pseudo-random code of the receiver is consistent with the phase of the received spread spectrum code,can the original information be recovered accurately.Direct sequence spread spectrum communication System(DSSS)is one of the most commonly used SSC systems.In order to improve the performance of information transmission in DSSS,how to achieve and ensure the consistency between the phase of local pseudo-code and the phase of received spread spectrum code has always been the focus of research.It is also the main part of this paper.Firstly,this paper expounds the development of spread spectrum technology and the development of pseudo-code synchronization technology at home and abroad,and points out the significance of research and content of this paper,and the theoretical basis and excellent performance of the SSC system are introduced,the principle of DSSS and the generation of pseudo-random sequence as pseudo-code and its excellent characteristics are introduced indetail.Several commonly used pseudo-random sequences and their properties are introduced,and the principle and related technology of pseudo-code synchronization are introduced in detail,which includes sliding correlation method,matched filtering method,delay phase-locked loop and so on.Subsequently,drawing on the concept of sliding correlation method and the idea of matched filter capture method,the overall design scheme of pseudo-code acquisition and tracking based on delay-locked loop is given.The FPGA development board of Xilinx company's zynq-7000 series is selected as the hardware development platform,the function code of the pseudo-code synchronization is written and realized by Verilog language in vivado environment,and the FPGA design and implementation of pseudo-code synchronization are also completed.In the process of pseudo-code synchronization based on delay phase-locked loop(DPLL),the relevant calculation amount is reduced and the feedback time of the system is saved,through the optimization design of the signal interception,difference frequency sampling and phase error extraction module.Finally,through the test,the synchronization of pseudo code is realized and the original information is restored successfully,which verifies the feasibility of the method of pseudo-code synchronization based on the DPLL.And aiming at the false alarm phenomenon of pseudo-code acquisition in weak signal,the acquisition process of pseudo-code in this paper is improved by using the processing gain of stochastic resonance(SR)system.The simulation results show that the detection probability of pseudo-code acquisition after improvement is 16% higher than that before,and the effect is more obvious in the noisy environment.