Investigation On Continuous Transverse Stub Array Antenna For High Power Microwave Applications

As the terminal of high power microwave(HPM)system,anenna directly determines the performance and application field of the system.In order to enhance the effect of high-power microwave on the target,it is necessary to tune the microwave frequency and adjust the direction of the microwave beam according to the different types and orientations of the target.To achieve the above goals,high-power microwave antennas are required to have wide bandwidth,large-range beam scanning capability and higher power handling capacity.However,the existing HPM antenna can not fully meet the requirements for applications in terms of working bandwidth and beam scanning range.In the thesis,the Continuous Transverse Stub(CTS)is introduced into the HPM field and two kinds of HPM array antennas are proposed and studied.The first one is the planar waveguide CTS array antenna,which can achieve a wide bandwidth and frequency tuning by optimizing the shape of the stub and introducing an engineering tuning structure.To realize higher power handling capacity,the structure of the CTS is improved and a feed network with stepped power distribution is designed.As a result,the sidelobe of the antenna along the direction of array formation is reduced,and the antenna can satisfy the requirement of HPM applications.The second one is the radial line waveguide CTS array antenna.The antenna acts as a feed antenna,together with the novel composite dielectric lens,the antenna system can realize a two-dimensional beam scanning in a large space range by only rotating the two lenses.This innovational work is summarized as follows:1.A broadband and tunable CTS array antenna fed by planar waveguide is proposed and studied.The antenna is fed by quasi-TEM mode,which has the characteristics of low profile,favorable conformal performance,easy array formation and wide working bandwidth.The theory and methodology for the design of the linear array are systematically studied.The method of expanding the antenna bandwidth is explored,and a tunable structure is proposed.Hamming function is used as the aperture distribution function,exhibiting the advantages of high gain,wide beam width,low sidelobe and high power handling capacity.A one-dimensional linear array operating at8.4 GHz in X band is designed and numerical simulations are carried out.The results show that the relative working bandwidth of the antenna could reach 19%and the bandwidth can exceed 39.5%after tuning.A broadband feed network and a dielectric isolation window are designed to feed the planar array with their bandwidths reach21.6%.The simulations of the whole radiation system are also carried out.When ingoring ohmic loss,the results show that more than 95%of the energy is radiated and the bandwidth of the system exceeds 19%,and the power handling capacity could reach1 GW.The radiation system has the potential to be applied to broadband HPM systems.2.A high power CTS array antenna fed by planar waveguide is studied.In order to achieve higher power handling capacity,the structure of CTS radiator is improved and the CTS linear array is redesigned.To reduce the sidelobe of the antenna in the direction of array formation,in this thesis,we propose the idea of feeding the planar array with stepped distribution currents.A feed network is designed which can realize stepped power distribution and equal output phase.The feed network is compact with the advantages of low reflectance,stable output microwave amplitude and small phase jitter.Numerical simulation of the feed network shows that its power handling capacity can reach 2 GW and the insertion loss is less than-30 d B.After that,a joint simulation of the feed network and the improved planar waveguide CTS array antenna is carried out.The results show that radiation system has a gain of 42.8 d Bi at 8.4 GHz,with a sidelobe of-19.9 d B and the beam width of 1.5°on the E plane.The sidelobe of the antenna is-17.8 d B and the beam width is 1.2°on the H plane.The radiation system can meet the requirements of practical applications.3.A circular aperture CTS array antenna fed by radial line waveguide is proposed and studied.The antenna includes 13 concentric rings of CTS slots,which has the characteristics of compact structure and high power handling capacity.The RL-CTSA can also act as the feed antenna of the beam steering system in addition to being used to radiate the microwave directly.In this thesis,the working principle and design process of the antenna are analyzed in detail.A prototype working at Ku band 14.25 GHz is designed and systematically simulated.In order to verify the performance of the antenna,a CTS array antenna is fabricated and experiments are carried out under low power conditions.The results show that the antenna can produce a pencial beam when the injection mode is circularly polarized coaxial TE₁₁ mode.The gain of the antenna is35.3 d Bi at the center frequency of 14.25 GHz,with a sidelobe of-21.6 d B.When the injection mode is TEM mode,its radiation pattern is doughnut-shaped with a boresight null.The main gain of the antenna is 32.63 d Bi,with a sidelobe of-15.0 d B.The electric field distribution at the antenna aperture is uniform,which can reach the expected goal.4.A neo-type of high power composite dielectric lens is proposed and studied.The lens is drilled with numerous elliptical holes and filled with dielectrics,which has a simple structure and a large beam-deflection angle.The phase-shift characteristic of the transmisson element is analyzed in detail and the structure of the elements is optimized through theoretical analyses and simulation.Three lenses are designed for the CTS array antenna,which can achieve beam converging and beam steering.A prototype,working at Ku-band,has been simulated,fabricated and measured to demonstrate the proposed methodology.It was found that all azimuth angles(0°-360°)and elevation angle in the range of 0°-45.6°can be covered.During beam steering,the reflection coefficient of the antenna is less than-15 d B at the central frequency,with only 1.7 d B gain variation from 38.1 d Bi peak value and the maximum aperture efficiency can achieve 80.5%.The simulated and measured results agree each other well and in agreement with the theoretical results.Moreover,high-power experiments are also carried out.The results show that the power handling capacity of the antenna exceeds250 MW and the antenna works normally under high power condition.Compared with the existing HPM beam steering antenna,the antenna has the the advantages,such as compactness,low cost,wide span range,and easy to control.