| With the development of wireless technology,there is more and more demand for planar antennas and waveguide antennas.Planar scan antennas face problems such as narrow scanning range and large fluctuation of scanning gain in the field of beam scanning,and waveguide slot antennas face problems such as large axis ratio and narrow beam in the field of circular polarization.In order to solve the above problems,many scholars have carried out extensive researches.In this thesis,for the purpose of improving the beam scanning effect of planar antenna and circular polarization performance of waveguide slot antenna,three beam scanning antennas with planar structure and two circularly polarized waveguide slot antennas are proposed.The specific research results of this thesis are as follows:The specific study of frequency swept antenna with planar structure is carried out,and the frequency swept principle is analyzed,and two frequency swept antennas with planar structure are designed by combining the theory of composite left-and right-handed transmission lines and the theory of equidistant surface excitations transmission lines.By using the periodic bending microstrip structure and loading the tuning branch,a wideangle frequency sweep antenna with continuous passband and continuous scanning characteristics based on the composite left-and right-handed transmission line is designed.The antenna can achieve a continuous beam sweep from +50° to-60° in the 5.5 GHz-6.4GHz band with a maximum gain of 12.68 d Bi and an in-band gain fluctuation of less than2.43 d B,meeting the requirements of wide sweep angle and small gain fluctuation;based on the artificial surface equipartition excitation transmission line loaded with a periodic modulation structure and shifting the high harmonics to the fast wave region to meet the radiation conditions.The antenna is capable of continuous scanning from-60° to +80° in the 5.05 GHz-6.05 GHz band with a maximum of 10.75 d Bi and gain fluctuation of 3.47 d B in the whole band,with ultra-wide scanning angle and small gain fluctuation.A specific study of beam-scanning super-surface with planar structure is carried out,the super-surface beam-scanning principle is analyzed,and a beam-scanning antenna based on 1bit digital reconfigurable unit is designed.The wideband patch antenna is fused with a single-blade double-throw switch design to obtain a wideband 1bit digital reconfigurable unit,and then a microstrip eight-way power divider feed is used to combine with an optimized coding sequence to obtain a 1bit digital reconfigurable unitbased beam scanning antenna.The antenna is capable of dual beam scanning from-48°to +48° with a maximum gain of 15.6 d Bi and a minimum gain of 10.3 d Bi.The gain fluctuation is 5.3 d B.The specific study of waveguide structure of circularly polarized waveguide slot antenna is carried out,analyzing the waveguide slot radiation principle,circular polarization principle,and designing two pure metal structure of circularly polarized waveguide slot antennas,respectively,the upstream antenna working in ka-band,and the downstream antenna working in ku-band.The slots are opened at the end of the waveguide,and the energy is coupled to the circular polarizer and then radiated out after the horn radiation element,and the circularly polarized waveguide slot antenna array is obtained after the formation of the array.Then use sixteen waveguide power splitter feed to verify the effect of circularly polarized waveguide slot antenna array.The two antenna arrays can realize the beam 3 d B edge gain more than 22.8 d Bi,3 d B beam width more than 52.6° in east-west direction and more than 2.813° in north-south direction in their respective frequency bands,and the axis ratio is less than 1.5 d B in 3 d B beam width with wide beam,low axis ratio and high efficiency. |
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