Research On Key Technologies Of High-power Linearly Polarized Helical Array Antennas

High-power microwave antenna is one of the important components of high-power microwave system,and the performance of high-power microwave antenna largely determines the performance of high-power microwave system.With the development of high-power microwave technology,high-power microwave antennas have also been continuously innovated.Among them,high-power helical array antennas are a typical type of high-power microwave antennas.Due to their high power capacity,high efficiency,and miniaturization,they are widely used.However,high-power helical array antennas usually radiate circularly polarized waves,and their applications are limited in scenarios where linearly polarized waves need to be radiated.In order to give full play to the advantages of high-power spiral antenna,this kind of antenna is used to realize linearly polarized radiation,which is of great significance to the research of high-power linearly polarized spiral array antenna.There are usually two ways to achieve linearly polarized radiation based on high-power helical array antennas;The first method is to realize linearly polarized radiation by loading a polarization conversion radome on the basis of conventional high-power helical array antennas.The second way is to study directly a helical element antenna that radiates linearly polarized waves,and realizes linearly polarized radiation through a matching feed system.Therefore,this paper focuses on the above two technical approaches to realize high-power linearly polarized helical array antennas to carry out related key technology research.The main work is as follows:1.Design and experiment of a high-power light-weight built-in curved meander-line polarization conversion radomeIn view of the lack of power capacity of the traditional meander-line polarization conversion radome,the existing high-power embedded polarization conversion radome is heavy in weight,and the environmental adaptability is not strong,a high-power lightweight built-in curved meander-line polarization conversion radome is proposed and studied.The high-power light-weight built-in curved meander-line polarization conversion radome isolates the influence of the external environment by means of a built-in meander-line,and improves environmental adaptability;by applying the curved meander-line structure to the meander-line polarization conversion radome,the electric field is reduced and the power capacity is increased;reduce the weight of the radome by replacing the material and removing the buried structure.The overall simulation and optimization of the built-in curved meander-line and the antenna sealing cover realizes the conversion of circularly polarized waves to linearly polarized waves.The radome is loaded above the high-power helical array antenna.After loading the radome,the axial ratio of the array antenna changes from 0.6d B to more than 20d B,and the gain is 24.2d Bi,which remains basically unchanged.The power capacity of the array antenna is 48MW.（Filled with SF₆gas at one atmospheric pressure,the same below）.According to the actual situation,the 44-element helical array antenna and the high-power built-in curved meander-line polarization conversion radome are processed.The experimental test of the array antenna loaded with the polarization conversion radome shows that the gain of the array antenna is 24d Bi,and the power capacity of the array antenna reaches 45.7MW.The experimental results are basically consistent with the simulation.2.Research on high-power helical element antenna that can directly realize linearly polarized radiationBased on the principle of superposition of left-handed circularly polarized waves and right-handed circularly polarized waves to synthesize linearly polarized waves,a high-power helical linearly polarized element pair and a high-power helical double-branched linearly polarized element are designed.The high-power helical linearly polarized element pair is composed of a left-handed helix and a right-handed helix.Through simulation analysis,the included angle,spacing,and helical reflective cavity of the helix pair are adjusted to obtain a high-power linearly polarized wave that can directly radiate.The linear polarization gain of this high-power helical unit pair is 10.9d Bi,the axial ratio is 40d B,and the power capacity is3.97MW.Based on the design idea of the double-branched helix,a high-power helical double-branched linearly polarized unit with two opposite branches is designed.By adjusting the diameter,angle,height,etc.of the two branches of the unit,a high-power helical linearly polarized unit that can directly radiate linearly polarized waves is obtained.The linear polarization unit has a reflection coefficient of less than 0.05 at the center frequency of 4.3GHz,a linear polarization gain is 8.65 d Bi,the axial ratio is 18 d B,a maximum electric field strength is 3973 V/m,and a power capacity is 3.8 MW.The helical element pair and the helical double branch linearly polarized element have higher power capacity and higher gain than the existing high-power linearly polarized antenna elements.3.Array antenna design based on high-power helical double-branch line-polarized unitBased on the above-mentioned high-power helical double-branch linearly polarized unit,a high-power linearly polarized array antenna is designed.The array antenna adopts helical double-branch linear polarization unit for radiation,and feeds the antenna unit through the rectangular waveguide fed at both ends,and the unit and the rectangular waveguide feed form a linear array fed at both ends.The linear array is fed through the radial line multi-channel rectangular waveguide power division network,and by adjusting the structure of the power division network and the coupling probe,the input of each unit basically maintains the same amplitude,and the high-power linear polarization of the array antenna is realized.Radiation,under simulation,the linear polarization gain of the array antenna reaches 27d Bi,and the power capacity reaches 47.7MW.