Research On High-power Polarization Conversion Radome And Circularly Polarized Phase Shift Surface

With the development of high-power microwave technology,the requirement of radiated antenna is no longer limited to high-power,but on the premise of ensuring high-power,the application demand of multi-function and multi-purpose is put forward for radiated antenna,including the requirement of polarization conversion and beam scanning.The embedded structure which can be used in high-power microwave radiation system is presented in the thesis,and the polarization conversion radome and circularly polarized phase shift surfaces are designed based on the embedded structure.By theoretical analysis,simulated calculation optimization and experimental verification,the polarization conversion and high-power handling capacity characteristics of the polarization conversion radome,and the beam scanning and high-power handling capacity characteristics of circularly polarized phase shift surface are respectively achieved.It lays a foundation for the research on the composite function of polarization conversion and beam scanning by using polarization conversion surface and phase shift surface.The thesis mainly focuses on the research of the high-power polarization conversion radome and the high-power circularly polarized phase shift surface.The main work can be summarized as follow:1.Design and analysis of the high-power polarization conversion radome.Aim at the low-power handling capacity of traditional polarization converters,a novel embedded meander-line polarization conversion radome is proposed.After the theoretical analysis of the transmission line model is completed,the simulation software is used to analyze and optimize the parameters of the unit structure.The results show that the bandwidth with polarization conversion effect can reach 7.1%.Simulation results of the unit and overall structure show that the conversion from circularly polarized wave to linearly polarized wave has been achieved without affecting other radiation characteristics when the beam scanning angle is equal to or less than 30°.The E-field intensity distribution in the condition of different radiation angles show that the theoretical power handling capacity of the polarization conversion radome is about 100 MW stably when the x-band radial line helical array antenna with 58 units is used as the feed antenna.By comparing with the power handling capacity of the traditional meander-line polarization conversion radome(4.5 MW),the effect of the embedded structure on improving the power handling capacity is verified.2.Development and experiment of the high-power polarization conversion radome.According to the actual processing conditions,the structure of the radome is optimized to a separated structure.Simulation results of the unit and overall structure show that the conversion from circularly polarized wave to linearly polarized wave has been achieved without affecting other radiation characteristics when the beam scanning angle is equal to or less than 25°.And the theoretical power handling capacity is maintained above 90 MW when the x-band radial line helical array antenna with 58 units is used as the feed antenna.The sensitivity analysis of the structure parameters of the polarization conversion radome shows that the change of the width of meander-line w has a great influence on the axial ratio after the polarization conversion,and the precision control of machining is guided by this.The test results of the polarization conversion radome show that the loading of the polarization conversion radome does not affect the other radiation characteristics.The test axial ratio after polarization conversion is about 17 dB in the condition of different radiation angles,which means that the circularly polarized wave is successfully converted to the linearly polarized wave.3.Design and analysis of the high-power circularly polarized phase shift surface.An embedded split ring phase shift structure is proposed based on the controllable phase characteristics of the phase shift surface.The simulation software is used to analyze and optimize the unit parameters of the phase shift structure.After rotating the optimized unit structure,the relative bandwidth of that the transmission coefficient is great than-1 dB is 3.6%.The 2 times relationship between rotation angle and phase-shift is described theoretically and simulated,and the positive and negative mapping relationship between incident circular polarization wave and rotation direction is summarized.Several single-layer phase-gradient surfaces with different angular beam deflexion are constructed based on the results of unit optimization.The simulation results show that the beam deflection at multiple angles are achieved by single-layer phase shift surface,and the the power handling capacity is maintained at about 10 MW when the x-band radial line helical array antenna with 58 units is used as the feed antenna.4.Research on beam scanning of the high-power dual phase shift surfaces system.The dual phase shift surfaces system with split ring is established based on the dual prism system model.Starting with the respective rotation angles of the dual phase shift surfaces system,the pitch angle and azimuth angle of the beam scanning are simulated by rotating the phase shift surfaces.Compared with the formula of the dual prism system model,the feasibility of applying the dual prism system model to the dual phase shift surfaces system is verified.On the contrary,starting with the pitch angle and azimuth angle of the beam scanning,the process of reversely solving the rotation angle of dual phase shift surface is described in detail and an example is given to illustrate the verification.The E-field intensity distribution of the dual phase shift surfaces system shows that the theoretical power handling capacity can achieve 30.5 MW when the x-band circular helical array antenna with 60 units is used as the feed antenna.The research on the high-power circularly polarized phase shift surface shows that the pitch angle of beam scanning of single-layer phase shift surface is fixed,and the trajectory of main beam after rotating the single-layer phase shift is a cone surface.While the pitch angle of beam scanning of dual phase shift surfaces system is more flexible and larger than that of single-layer phase shift surface.The trajectory obtained by rotating the double phase shift surfaces system is a cone,which realizes the flexible control of beam scanning.