| The electromagnetic scattering characteristics of radar targets are the basis for radar to detect and identify targets.Different targets have different reflectivity and scattering mechanisms for electromagnetic waves.By analyzing the scattering echo signal of the target,the millimeter wave radar can extract the electromagnetic scattering characteristics of the target and compare it with the target feature library,and then classify and identify the target.Passenger vehicles are the main participants in road traffic.Studying the target characteristics of passenger vehicles is of great significance for reducing road traffic accidents.However,due to the large size,complex structure and material of passenger vehicles,there is little research on the electromagnetic scattering characteristics of passenger vehicles.In order to improve the accuracy and efficiency of millimeter wave radar target classification and recognition,based on the target electromagnetic scattering theory and the working principle of millimeter wave radar,the influence factors of near-field electromagnetic scattering characteristics of passenger vehicles are analyzed.The electromagnetic scattering characteristic measurement system of passenger vehicle is developed.The radar cross section(RCS)measurement methods and scattering center location methods of passenger vehicle are designed,and the electromagnetic scattering characteristics of the Volkswagen polo were tested,which verifies the effectiveness and feasibility of the test system and method.Aiming at the research on electromagnetic scattering characteristics and testing methods of passenger vehicles,the main work of this paper is as follows.(1)The factors affecting the electromagnetic scattering characteristics of passenger vehicles were analyzed.Based on the target electromagnetic scattering theory and the principles of millimeter wave radar positioning and target feature measurement,the basic concepts and testing principles of two performance indexes of electromagnetic scattering characteristics of passenger vehicles,including radar cross section and scattering center,are introduced.Combined with the working mechanism of the vehicle millimeter wave radar,the scattering electromagnetic field characteristics of the passenger vehicle are analyzed,and the influence factors of the electromagnetic scattering characteristics of the passenger vehicle in the electromagnetic near-field are analyzed.(2)The testing system of electromagnetic scattering characteristics of passenger vehicles was developed,verified,and analyzed.Based on the influence factors of near-field electromagnetic scattering characteristics of passenger vehicles,an outfield static test system based on 77 GHz frequency-modulated continuous wave(FMCW)vehicle radar was developed,other main equipment includes metallic sphere reflector and trihedral reflector and their low interference bracket,rotating platform for supporting passenger car rotation,and data processing unit based on STM32 development board and C# programming language.In order to verify the effectiveness of the system,the influence of the rotating platform and the motion state of the passenger vehicle on the electromagnetic scattering characteristics of the passenger vehicle in the electromagnetic near-field static test was analyzed,and the measurement quality of the system was evaluated.(3)The test method of electromagnetic scattering characteristics of passenger vehicles is designed,the electromagnetic scattering characteristics of Volkswagen polo were tested,and the test results were given.Based on the developed test system,the methods of measuring of quasi-far-field radar cross section and locating the spatial location of scattering center of the passenger vehicles were designed.The main sources of measurement uncertainty in the static testing process of near-field electromagnetic scattering characteristics of passenger vehicles were analyzed.The quasi-far-field distance and the radar cross section at quasi-far-field of Volkswagen polo were measured.The scattering echo signals at the front,side and rear of the vehicle are measured,and the scattering center of Volkswagen polo is located.The test shows that the test system and method are effective and feasible.And through the analysis of uncertainty,it provides a theoretical basis for the subsequent testing technology of electromagnetic scattering characteristics of passenger vehicles. |
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