Novel High Power Microwave Scanning Array Antenna

The output power of a single high power microwave?HPM?source is difficult improve due to its inherent physical limitations.Higher equivalent radiation power can be achieved through the coherent combination of spatial power.While spatial power coherence synthesis?SPCS?puts forward new requirements for high power microwave antennas.It requires not only high power capacity and high radiation gain,but also modular,compact structure design,low manufacturing cost,and beam scanning capability.The existing high-power microwave antenna can not meet the requirements for applications in terms of beam scanning range,manufacturing cost,and compact structure.In the thesis,two novel beam scanning array antennas are proposed and studied.The first one is the decentralized conical scanning array antenna which is based on the principle of near-field phase conversion.,Two-dimensional beam scanning is achieved by rotating the feed array surface and dielectric lens.The second one is the array antenna with decentralized line and column scanning.The array antenna is based on the coupling feed of the narrow slots in a rectangular waveguide where a helical element is used as radiation unit and a helix structure of the same line helical unit is jointly rotated.The initial phase of the injected microwave in each waveguide is adjusted by a phase shifter network,which enables two-dimensional beam scanning with line-and-column control.In this thesis,theoretical analysis and numerical simulations are carried out,and some structures are experimentally studied.Specific work includes:?1?A decentralized conical scanning array antenna is proposed and studied.The array antenna consists of a feed array antenna and a dielectric lens.The feed antenna is a radial waveguide slot-coupled helical array antenna,the basic principle and the design process of the radial waveguide slot-coupled helical array antenna are analyzed in detail,and an antenna with a diameter of 600 mm and a total of 17 concentric ring arrays is designed.The designed model at Ku band 14.25 GHz is systematically simulated,and the results of numerical calculations and theoretical analysis show that the reflection of the radial waveguide slot-coupled helical array antenna is less than-20.0 dB,the aperture efficiency is more than 70.0%,the maximum beam inclination deviation from the normal direction is 20 degrees,and the power capacity is 600 MW.Elliptical hole array filled with dielectrics is adopted as the lens,the properties of which are studied through numerical simulations.The results show that the maximum beam inclination angle of the dielectric lens is 22 degrees and the power capacity is more than 500 MW.In addition,the joint simulation of feed array antenna and dielectric lens is also carried out.The results show that the decentralized conical scanning control is realized by rotating feed array antenna and dielectric lens.Two-dimensional beam scanning is achieved by the array antenna in the conical angle range of 90 degrees and the system reflection is less than-22.0 dB.?2?A linear array antenna fed by narrow slot coupling in rectangular waveguide is proposed and studied.The linear array antenna is foundation of the array antenna with decentralized line and column scanning.In order to realize one-dimensional beam scanning,a method of one-dimensional beam scanning along the wide-edge plane of rectangular waveguide is proposed using narrow-edge slot coupling feed of rectangular waveguide,helical element as radiation element.,One-dimensional beam scanning is achieved by rotating helix structure.The theory and methododology for the design of the linear array are systematically studied.The problems of antenna reflection and beam drift are solved.A one-dimensional linear array working at 9.4 GHz in X-band is designed and numerical simulations are carried out.The results show that the reflectance of the linear array is less than-25.0 dB,the scanning range of one-dimensional longitudinal beam is within±30 degrees,the side lobe level is less than-10.0 dB,and the main lobe gain variation is less than 1.5 dB.In order to meet the needs of later array formation,a linear array antenna working at 8.4 GHz with 100 radiation elements is also designed and fabricated and the experimental study of the linear array antenna is carried out.The experimental results show that the S parameters of the linear array are in agreement with the simulation results.The antenna reflection is less than-35.0 dB,the gain of linear array measured by comparison method is 28.4 dB.The one-dimensional beam scanning characteristics of linear array antenna are also studied experimentally.The main lobe performance of the antenna is maintained well in the range of±35 degrees and the gain variation is less than 2.5 dB.However,the cross-polarization component lobe level of the system reaches-8.0 dB.Besides,the cross-polarized lobe which is caused by processing error of helix.is analyzed.,The improved helix structure and a different processing technology are recommended.?3?A new type of waveguide phase shifter with rotating adjustment is proposed and studied.The phase shifter is based on a narrow slot bridge in a rectangular waveguide.By converting the linear polarization mode into the circular polarization mode,the phase of the reflected circular polarization mode wave is controlled by the rotating joint at the end.The characteristics and operatingprinciple of the rotationally adjustable waveguide phase shifter are analyzed in detail and simulation results are presented and analysed.It shows that continuous linear phase adjustment can be realised by the phase shifter and the return loss is less than 0.1%.A phase shifter working at 8.4GHz is fabricated and verified experimentally.The experimental results show that the linear phase adjustment can be realized in the non-resonant state and the energy transfer efficiency is more than 95.0%.However,the resonance phenomenon exists in individual states.After optimising the structure of phase shifter,the resonant mode can be effectively suppressed by radiating the resonant mode through the waveguide slot.?4?An array antenna with decentralized line and column scanning is proposed and studied.The array antenna consists of three parts:power division network,phase shifter network,and radiation array.The power division network adopts the mode of circular waveguide TM₀₁-TE₀₁-rectangular waveguide TE₁₀.The numerical simulation results show that at 8.4 GHz,a 20-channel power sharing is achieved.The insertion loss is less than-0.4 dB and the power capacity is about 1.5 GW.Based on the phase shifter and radiation waveguide,the array antenna system with decentralized line and column scanning is built.A simplified model of 20×15 rectangular grid array consisting of 20rows of waveguides with 15 radiating elements on each row of waveguides is established in numerical simulations.The two-dimensional beam scanning capability of radiation array is studied systematically.The results of numerical simulations show that the array antenna can achieve beam scanning in the range of±35 degrees in one-dimensional plane which is perpendicular to the waveguide axis,with sidelobe level below-12.0 dB and gain variation less than 2.0 dB.In the one-dimensional plane along the wide edge of the waveguide,beam scanning can be achieved in the range of±30degrees.The sidelobe level is less than-10.0 dB and the gain fluctuation is less than 1.5dB.