Research On Acquisition Technology Of Non-coherent DSSS Signal

The technology of non-coherent direct sequence spread spectrum(DSSS)is widely adopted in telemetry,tracking and command(TT&C)communication system for the telemetry and remote control signals.In this system,the clocks of the pseudo-random(PN)code generator and data source are not homologous.The relative relationship between the data bit transition edge and the PN code phase is indefinite,which makes the signal acquisition difficult.Since the correlation peak split and peak reduce in signal acquisition resulted from non-coherent data modulation,this thesis proposed an improved acquisition algorithm based on the research of traditional capture algorithms.The algorithm uses the correlator group with equal intervals at the starting points of the integration,and through the multiplexed FFT-IFFT module and pipeline processing,it can accurately detect the edge of the data bit and capture the pseudo code.In this thesis,the simulation between the proposed acquisition algorithm and the traditional acquisition algorithm is completed under different SNR conditions,including the acquisition result,the correlation peak-to-peak ratio curve and the mean value of the detection noise.Simulation results show that the proposed acquisition algorithm can effectively capture non-coherent DSSS signals,greatly improve the anti-noise performance under low SNR,and the average noise amount of detection is relatively stable.The proposed acquisition scheme was implemented on Xilinx FPGA.The key module design of the acquisition scheme and the functional simulation under the ModelSim software were described in detail.The online logic analyzer ChipScope was used to test and verify the design of this thesis.