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

The linear FM short-range detection system has the advantages of high ranging accuracy,no distance blind zone and strong anti-interference.So it has been widely used in military and civil fields.This paper studies the signal processing technology of saw-tooth wave FM near-range detection system,which mainly includes the high precision range measurement,speed measurement and angle measurement technology of the saw-tooth frequency modulation short-range detection system.Firstly,by analyzing the beat signal of saw-tooth wave FM short-range detection system,ranging algorithm based on linear FM-Z transform(CZT)and speed measuring scheme based on time domain due to the sampling theorem are designed.Then,according to the analysis of the phase relationship between the two beat signals in the process of one sending and two receiving system and the phase relationship between the two Doppler signals,the angle measurement scheme is designed which is based on FFT phase difference measurement method.The effectiveness of the range,velocity measurement and angle measurement algorithm is verified by simulation,which shows that the proposed method can be used for high precision measurement in these fields.Secondly,hardware and software design of the signal processing system is based on the system scheme and specification requirements.Hardware design mainly includes the chip selection,schematic design,PCB design,components welding and testing modules.And software design mainly includes the implementation of the Field-Programmable Gate Array(FPGA)in aspects of the range measurement,velocity and angle measurement scheme of signal processing system,by the process of programming,compiling,pre-simulation,modification,post-simulation,and function verification.Finally,after connecting the signal processing board with the antenna of the radio frequency module into a complete system,the field experiments of range and velocity measurement is conducted successfully.The experimental results show that the accuracy of signal processing system range measurement is up to 0.1m and 0.01 m/s for velocity measurement,which meet the requirements of system index.Besides,angle measurement experiment is conducted in the laboratory and the result shows that the accuracy of angle measurement is 1.5°,which also meets the requirement of system index.