Design And Implementation Of Baseband Signal Processing In M-ary Spread Spectrum Systems

Because of its strong anti-interference,anti-fading,anti-multipath performance,high frequency spectrum utilization,and multi-access communication,spread spectrum communication systems are attracting more and more attention.In some practical applications where the channel bandwidth is limited and high concealment is required,conventional spread spectrum communication technologies cannot meet the requirements.However,M-ary spread spectrum can be well applied in the occasions where the channel bandwidth is limited and the concealment is very high,so M-ary spread spectrum technology has gradually become the focus of research at this stage.The main content of the thesis contains the following aspects:(1)Because of M-ary spread spectrum communication system requires a large number of available codes and good sequence correlation,this thesis studies the auto-correlation properties ? cross-correlation properties of m sequence and Gold sequence.Based on the actual project requirements and the proposed baseband signal processing scheme combined with the basic principle of pseudo-random code selection,finally,the thesis designs a Gold code that meets the system requirements and carries out a simulation verification of the correlation of the designed Gold code.(2)This thesis studies the M-ary spread spectrum system,combine with engineering requirements,it analyzes the index requirements of baseband signal processing technology for M-ary spread spectrum communication systems.The baseband signal processing scheme for the M-ary spread spectrum communication system is designed.At the same time,the parameter configuration of the system was determined through simulation.Moreover,the theoretical performance of the M-ary spread spectrum communication system designed in this thesis is analyzed by simulation.(3)The synchronization technique of the spreading code is studied in this thesis.According to the requirements of the system specification and the requirements of the baseband signal processing technology,the sliding correlation detection method and the tracking code acquisition and tracking scheme of the non-coherent delay locking code tracking loop are designed.The simulation results of the capture performance of the sliding correlation acquisition method designed in this thesis and the tracking performance of the non-coherent delay locking code tracking loop are also analyzed.(4)This thesis focuses on the disadvantages of M-ary spread-spectrum systems against narrow-band interference that exceeds spread-spectrum gains.At the same time,the anti-narrow-band interference techniques are studied in conjunction with system design requirements,and anti-narrow-band interference techniques are designed by analyzing the principle of anti-narrow-band interference techniques.At last the thesis conducts a simulation analysis of the program's performance.(5)Aiming at the baseband signal processing scheme of M-ary spread spectrum communication system designed by the thesis,this thesis implements the hardware design of the system with FPGA.At the same time this thesis gives the hardware design of each module and the hardware program running results.The important modules designed in this thesis and various performance indicators were tested to verify the correctness and feasibility of the system.