Research On High Power Microwave Planar Array Antenna

As one of the key technical links of the high power microwave application system,the main function of the system is to complete the efficient feeding of microwave power from the transmitter to the antenna and to realize the directional radiation.At present,most high-power microwave sources have axisymmetric high-frequency structures,such as the virtual cathode oscillator,relativistic backward wave tube,gyrotron and so on,the mode of their work is mostly used as circular waveguide mode,TEOn and coaxial mode.The direct radiation patterns of these modes all show the phenomenon of central axis depression,which is not conducive to long distance directional radiation.Therefore,most of the current high-power microwave sky feed links are used to convert the axisymmetric mode of work into a circular waveguide TE11 mode first with a mode converter,and then large aperture feed and reflector antenna are used to achieve high gain radiation.In reality,there are some technical defects such as complex link structure,huge volume,difficult surface processing of reflector antenna.Flat plate antenna is a new type of antenna technology proposed in the world in recent years.It realizes the effective control of the phase of electromagnetic wave by using the diffraction periodic structure,and realizes the specific radiation characteristics.1.The working mechanism of planar array antenna with diffraction periodic structure is studied.The contradiction between the phase shift and the insertion loss of a single layer transmission array is derived from the theoretical point of view,and the number of layers of the diffraction periodic structure is determined by combining the technical requirements of the variable mode antenna.As the element parameters determine the macro parameters of the antenna,in order to accurately grasp the electromagnetic characteristics of the diffraction unit,this paper presents two typical unit simulation methods in the present world.It is pointed out that the periodic model has a larger adaptive range than the equivalent waveguide model,and it can give the phase shift characteristic under the condition of the oblique incidence,which lays a theoretical foundation for the precise control of the phase shift of the variable mode antenna.2.On the basis of many performance indexes,such as low insertion loss,large phase shift range,high polarization isolation,high power capacity,and so on,the variable size"+" slot structure unit is selected.The parameters such as cell period,slot width and thickness of air layer have been optimized.Finally,the ideal antenna unit performance is obtained.3.On the basis of the optimization of the unit parameters,the field distribution and polarization characteristics of TM01 mode and quasi HE11 mode are compared and analyzed,and the study on the theory of variable polarization based on the diffraction periodic structure is carried out.At the same time,in order to improve the spatial feeding efficiency of the TM01 mode to the transmission array and reduce the primary sidelobe,the design of the primary radiator based on the corrugated horn structure is also completed.The model transformation antenna array of 16X16 unit is designed by using the above unit and radiator,and the validity of the antenna is verified by the simulation software.The simulation results show that the antenna can complete the quasi mode conversion well and the antenna simulation gain can reach 22.5dB.4.The structure design and processing of the 16X16 array antenna are completed,the aperture of the array is 260.8mmX260.8mm,and the space field scanning test system and the far field direction map test system are set up to carry out the detailed experimental research on the machining model.The experimental results are in good agreement with the simulation.The polarization rate of the mode transformation antenna is 96.8%,and the antenna gain is 22.3dB.