Design Of Low Sidelobe Array Antenna In Vehicle Mounted Radar

Cars,the main means of transportation in many countries,are becoming more and more popular.At the same time,more and more traffic accidents have also attracted the attention of people.With the development of technology,the vehicle mounted radar technology has received more and more attention by automobile manufacturers and research institutes.At present,24GHz and 77GHz frequency bands are mainly used in vehicle mounted radar in the market.24GHz radar is applied for short range radar,but 77GHz radar can be used in short range radar and long distance radar.In this thesis,we mainly study the antenna used in 24GHz and 77GHz vehicle mounted radar.According to the actual needs of the project,a 8 X 6 array is used in the antenna of 24GHz vehicle mounted radar and using the Chebyshev synthesis method to reduce the side-lobe level.Because more narrow beam width and higher gain is needed in the 77GHz microstrip antenna array,we choose a 12 X 16 array,and we use Taylor synthesis method to reduce the side-lobe level.In the design of the line array,an array of unequal array elements is used in this thesis.We use the patch width weighting method and change the amplitude distribution of the current by adjusting the width of the rectangular patch unit to realize the predetermined current distribution.In the design of the planar array,the impedance transformation section method is used in this thesis.The impedance transformation section is added to the main feeder line and we adjust the width of the impedance transformation section to change the proportional relationship between the admittance of the transformation section and the transmission line admittance for realizing the current coning and reducing the side-lobe level.The bandwidth of the 24GHz microstrip array antenna is greater than 250MHz and the gain is greater than 18dBi.The half power beamwidth for E plane is less than 15 degrees and the side-lobe level is less than-18dB.Besides,the half power beamwidth for H plane is less than 20 degrees and the side-lobe level is less than-18dB.The gain of the 77GHz microstrip array antenna is greater than 24dBi and the bandwidth is greater than 800MHz.The half power beamwidth for E plane is less than 10 degrees.Besides,the half power beamwidth for H plane is less than 17 degrees.The side-lobe level for E plane and H plane is less than-20dB.