Research On Signal Processing Technology Of Chaotic Phase Modulation And Linear Frequency Modulation Compound Short-range Detection System

The chaotic phase-modulation signal has the advantages of no fuzzy distance,strong anti-interference and anti-interception ability.The chirp signal has the advantages of high ranging accuracy and no distance blind zone.The combination on signal of the chaotic phase-modulation and linear frequency modulation puts the advantages of these two signals,whose form is complex.And the anti-interference performance of the system is enhanced,the interception probability of the system is reduced,and the accuracy of the distance and speed measurement of the system is improved.This thesis mainly studies the signal processing technology of chaotic phase-modulation and linear frequency modulation composite short-range detection system.The main tasks as follows:Firstly,the workflow of the chaotic phase-modulation and linear frequency modulation composite short-range detection system is discussed and the signal expressions of each level are derived.According to the requirements of the indicators and the characteristics of the signals,the system parameters are analyzed and determined,the system model is built.Secondly,by analyzing intermediate frequency(IF)signals,a distance-determination algorithm based on chaotic code correlation is studied.By analyzing the difference frequency signal and the doppler signal,a ranging algorithm based on homomorphic filtering and a speed measurement algorithm based on time-domain undersampling are proposed.The simulation results show that these algorithms have higher accuracy of distance and speed measurement.The analysis results show that by using the distance-determination and ranging methods to obtain the distance information can enhance the anti-jamming performance of the system.Then according to index requirements and signal processing scheme,the software and hardware design and test of signal processing part are completed.The hardware is mainly for FPGA configuration circuit,power system circuit,clock reset circuit,AD conversion circuit and DA conversion circuit,including Schematic design,PCB board drawing and welding debugging.The software is programmed on the programmable logic array(FPGA)based on Verilog HDL language.It is mainly for distance-determination,distance and speed measurement algorithms,including program writing and board level debugging and verification.Finally,in the laboratory,the method of generating analog IF signals was designed,and the experiment of distance-determination,distance and speed measurement were completed..The results of experiment show that the distance-determination experiment's accuracy reaches 1m,the distance measurement experiment's accuracy reaches 1.5m,the speed measurement experiment's accuracy reaches 2m/s,which meet the requirements of the system indicators.