| In order to reduce the incidence of traffic accidents,automotive anti-collision radar is applied to all kinds of vehicles.Antenna is the front-end equipment of the transmitting and receiving device in the automobile anti-collision radar system.The gain,side lobe level and bandwidth of the antenna determine the detection range,anti-jamming ability and measurement accuracy of the system.Microstrip antenna is widely used in automotive radar because of its small size and easy mass production.In this paper,the 24 GHz microstrip array antenna is studied according to the practical application requirements of vehicle anti-collision radarFirstly:A dumbbell shaped defected ground structure is designed to improve the isolation of microstrip transceiver antenna.Due to the limited volume and space,the distance between the two antennas is very close.The surface wave generated on the surface of the dielectric substrate will aggravate the coupling between the two antennas and worsen the radiation performance of the antenna.In this paper,a dumbbell shaped defected ground structure working at 24 GHz is designed based on the isolation principle of microstrip transceiver antenna and the characteristics of defected ground structure,and the variation of bandgap frequency with different sizes of structure is analyzed.Finally,the designed defected ground structure is cascaded between the transmit and receive antennas,the coupling suppression effect is obvious,and the minimum coupling coefficient is-58 db in the working frequency,which proves the feasibility of the structure.Secondly:A microstrip array antenna for vehicular continuous wave radar operating at 24 GHz is designed.According to the needs of the project,the 8×8 planar array is designed.Each radiation unit is a simple rectangular patch,and a planar array is formed by a series parallel hybrid feed network.The purpose of impedance matching is achieved by adding a quarter impedance transformation section to the feeders between units.This structure is flexible and convenient to control the current distribution.Finally,the simulation results show that the antenna structure has the characteristics of small size,high gain and easy integration.Thirdly:An antenna array composed of four groups of antennas is designed.According to the principle of spatial power synthesis,four groups of antennas are cascaded.Considering the performance of antenna array,such as total gain,sidelobe level and isolation,the application of four groups of antennas in array is studied.Two kinds of antenna arrays,rectangular array and rotary array,are designed,their performances are simulated and analyzed,and their advantages and disadvantages are compared from many aspects,which provides a good reference for the antenna array of radar system. |
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