Design Of A Signal Processing System For Pseudocode Phase Modulation And Linear Frequency Modulation Composite Short-range Detection Based On FPGA

The composite short-range detection system not only has the advantages of high ranging accuracy and no distance blindness,but also has the ability of excellent anti-interference and accurate ranging under high-speed conditions,so it has attracted application range.In the thesis,the pseudo-code phase modulation(PM)with linear frequency modulation(LFM)composite short-range detection system mainly studies the high-precision ranging measurement and speed measurement technology and the anti-interference performance.Firstly by studying the working principle of the composite system,the principle of system parameter selection is determined.MATLAB/Simulink was used to simulate the signal reception process of the composite system and analyze the spectrum characteristics.Ranging algorithm based on the autocorrelation processing of the part of pseudo-code PM system and based on CZT of LFM system and speed measurement scheme based on the under-sampling are designed,and compares the advantages and disadvantages of two measurement algorithms,which are verified by simulation.Then deducting the SJR gain of input and output the anti-interference performance of the complex system is analyzed.Based on the simulation analysis,the influence degree of the ranging speed affected by noise amplitude modulation and noise frequency modulation interference is obtained,and the results show that the anti-interference performance of the composite system is better than the single system.Secondly the software and hardware design and testing of this system are completed according to the system requirements.Hardware design includes components selection,schematic design,circuit-board layer design,circuit-board welding and hardware circuit board test.FPGA was used to complete the software design,including module design,software writing and simulation verification.Final the circuit board is used for the experiment,the intermediate frequency signal is input,and the ranging and speed measurement experiment is carried out in the laboratory.The experimental data shows that the ranging accuracy of the relevant detection is up to 0.15 m,the CZT difference frequency ranging can reach 1.5m and the accuracy of speed measurement for 1.5m/s,which meet the requirements of the subject index.