Research On Specific Beam Broadening Technology Of Single Fed Broadband Circular Polarization Antenna

With the development of wireless communication system,circularly polarized antenna has been widely used in satellite communication,radio frequency identification,radar and other fields because of its excellent performance in reducing polarization mismatch and suppressing multipath effect compared with linear polarized antenna.In order to satisfy the higher transmission rate and system capacity,broadband antenna has become a hot spot in antenna research.In addition,in order to obtain more stable wireless communication quality,the antenna is required to have a wide 3-dB Axial Ratio Beam Width(ARBW).Typically,feed-net design is required to implement broadband and wide 3-dB ARBW,but this increases the complexity and design difficulty of the system and introduces additional errors.Therefore,supported by liao ning Provincial Natural Science Foundation of China(2020-MS-127),this thesis studies the specific beam broadening technology of single-fed broadband circular polarization antenna and achieves the following results:(1)A single fed wideband circularly polarized dielectric resonator antenna with a width of 3-dB ARBW is proposed.The antenna consists of a cylindrical dielectric resonator loaded with a cylindrical air cavity,an orthogonal groove with a curved arm and an off-center L-shaped microstrip line.By etching orthogonal slots with curved arms in the floor and loading cylindrical cavities inside the DRA,the antenna’s 3-dB ARBW is effectively improved and symmetric radiative directivity is achieved.The measurement results show that the impedance bandwidth of the antenna is 33.3%,the circular polarization bandwidth is16.1%,and the 3-dB ARBW in the circular polarization bandwidth range is more than 150°.The antenna has simple structure and high circular polarization purity,which is suitable for circular polarization applications with wide beam coverage.(2)A 3-dB ARBW single-fed broadband circularly polarized microstrip antenna is proposed.The main radiator of the antenna is a monopole antenna.Circularly polarized radiation is obtained by placing vertical branches on the slotted floor.By loading L-shaped branches on the slotted floor,the axial ratio bandwidth and 3-dB ARBW of the antenna are effectively extended.The measurement results show that the impedance bandwidth of the antenna is 41%,the 3-dB axial ratio bandwidth is 47%,and the 3-dB ARBW in the circular polarization bandwidth range is more than 90°.The antenna has good circular polarization performance in the wide band range and is small in size,so it is suitable for highly integrated broadband circular polarization applications.(3)A single fed broadband polarized reconfigurable microstrip antenna based on liquid metal is proposed.By controlling horizontal current based on liquid metal,left circular polarization,right circular polarization and linear polarization are realized.By etching two rectangular slots on the back of the dielectric substrate,the impedance bandwidth of the antenna is improved.The 3-dB ARBW of circular polarization is improved by introducing tangent angles around the large rectangular slots and short branches between the two rectangular slots.The measured results show that the impedance bandwidths of the antenna are 62% and 67%,and the 3-dB axial ratio bandwidths are 39% and 43%,respectively,under the conditions of left and right circular polarization,and the 3-dB ARBW are all over 80°.The total impedance bandwidth of the test is 39.7 % in the online polarization state.