| From the 21 st century,various cars can be seen everywhere.Therefore,people’s travel safety has become the focus of attention,giving birth to the emergence of millimeter wave vehicle collision avoidance radar.Most of millimeter wave antenna arrays are mainly work at 24 GHz,77 GHz and 79 GHz and in the form of microstrip array antennas,which can achieve different gains and beam widths according to system requirements.The microstrip seriesfed antenna array is studied in this thesis.Based on the relationship between the network S parameter and energy transmission,a design method of the microstrip array antenna is showed.The specific design method is to equate each antenna element in the array as a dual-port network and the last element as a single-port network.According to the size of the radiation energy of each antenna unit and the relationship between the S parameter and the energy,the size of the transmission coefficient of each patch unit is gradually derived,while the reflection coefficient of each unit is minimized.The microstrip array antenna is designed by adjusting the length of feeder so that each unit radiates in the same phase,and the design of the microstrip array antenna is realized.Based on the above method,two antenna arrays with constant amplitude,inphase and low sidelobe working in the 24 GHz frequency band are mainly designed in this thesis.The antenna arrays are simulated in the full-wave simulation software HFSS to verify the effectiveness of the method.According to the requirements of the antenna specification the 5-element constant amplitude in-phase radiation microstrip series-fed array antenna is selected as the target antenna,and the RO4350 with a thickness of 0.254 mm is selected as the dielectric substrate.Series-fed is adopted in linear array,and HFSS and ADS joint simulation is used to match the antenna.The simulation results show that the operating frequency band of the antenna is 23.8-24.3GHz when the standing wave is less than 2,and the relative bandwidth is 2%.The gain of the antenna array is 13 d Bi,and the half-power lobe width of the E-plane and H-plane are20° and 66°,respectively,and the sidelobe level of the E-plane is-12.5 d B.After scaling it down,a 4-element linear array working at 2.4 GHz is designed,and the substrate is F4 B with a thickness of 1.5 mm.The simulation and test results show that the operating frequency band is 2.38-2.42 GHz with 1.6% the relative bandwidth.And the antenna gain is 12.48 d Bi,and the half-power lobe widths on the E and H sides are 25°,67°.In order to meet the requirements of long-distance radar testing,the azimuth and elevation planes of the vehicle radar antenna should meet the requirements of high gain and low sidelobe.Series-fed is adopted in azimuth plane,and in order to achieve low sidelobes,the power of each unit satisfies the Chebyshev distribution.1 minute 4 unequal division power divider in parallel is applied in elevation plane.ADS and HFSS joint simulation is used to optimize the design of antenna.Simulation results show that the antenna gain is 17.5 d Bi,and the working bandwidth is 23.62-24.15 GHz with 2.2% relative bandwidth.The azimuth angle and pitch angle are 22° and 24°,respectively.The E-plane sidelobe level is-14.5 d B,and the H-plane sidelobe level is-17.5 d B,which meets the array antenna index requirements of high gain,low sidelobe and narrow beam. |
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