| Phased array antennas have been widely used in communication,radar and other fields with their unique advantages such as fast and flexible beam scanning and strong ability to track targets.With the development of satellite Internet technology,vehicle-mounted,ship-borne,and air-borne satellite terminal stations require phased array antennas to have a wide-beam scanning range and still have a high gain in the range of low elevation angles.There is an urgent need to study circularly polarized phased array antennas with ultra-wide scanning angles.This thesis focuses on the needs of satellite Internet system terminal stations,and conducts wide-beam circularly polarized antenna unit and antenna array research.The main research work and innovations are as follows:(1)A wide-beam circularly polarized microstrip antenna loaded with a parasitic metal cavity and a three-dimensional ground is proposed.This antenna has a broad half-power beam width,simple structure and low processing difficulty.The simulation results and actual measurement results also verified its wide beam performance.The antenna gain is 2.2d B at5 GHz,and its beamwidth can reach 120° or more,laying the foundation for the subsequent wide-angle scanning array.(2)Based on the above wide-beam circularly polarized microstrip antenna,a 64-element two-dimensional circularly polarized wide-angle scanning microstrip antenna array is designed,and sequentially rotated feeding technology is used to improve the circular polarization axis ratio performance of the array.The simulation results show that when the array scanned to 60°,the antenna gain is only reduced by 4.7d B compared to when it not scanned.The axial ratio of the main lobe is always less than 4d B during the scanning process,indicating the circular polarization performance maintained well.Combining the simulation results of the array scanning of Phi0 plane and Phi90 plane,it is shown that the beam scanning range of the antenna array can reach ±60°.(3)An ultra-wide beam crossed dipole antenna structure for K-band phased array is proposed.Four vertical parasitic structures are loaded around radiating dipole arms and the beamwidth is broadened by the complementary antenna concept.Different from the abovementioned wide-beam circularly polarized microstrip antenna,this antenna has a higher working frequency,which results in a smaller antenna size and cannot be fed back with conventional feeding methods.Therefore,the dielectric layer is used innovatively instead of the air layer.The via process of PCB technique solved the power feeding problem.Both the simulation results and the actual measurement results verify that the half-power beamwidth of the antenna can reach more than 150°.(4)Based on the proposed ultra-wide beam crossed dipole antenna,a K-band twodimensional circularly polarized wide-angle scanning antenna array is designed,and the rotating feed technology is used to improve the circular polarization axis ratio performance of the array antenna.The simulation results of the array scanning of Phi0 plane and Phi90 plane show that when the array scanned to 75°,the antenna gain is only reduced by 5.3d B and 5.1d B compared with that without scanning,and the axial ratio is always less than 4d B,indicating that the antenna array has two-dimensional circular polarization wide-angle scanning performance with beam scanning range up to ±75°. |
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