Research On High Power Microwave Three-Band Snake Bends Mode Converter

Due to the special working mechanism of the high-power microwave source;the outputed modes are usually a rotating axisymmetric structure,such as the circular waveguide TM01 and the coaxial TEM mode.The beam is scattered during direct radiation,and the maximum directional power transmission in the boresight direction cannot be formed,then the effect of the target is reduced.The high-power(HPM)mode converter can convert the axisymmetric mode to the TEn or Gaussian mode which are suitable for radiation,combine with the antenna can realize high directional radiation.It is the core device to solve the above technical problems,and has been studied by scholars at home and abroad for a long time.With the development of HPM system application requirements,a single HPM device is limited by mode competition and physical performance limitations,and cannot meet the complex requirements of higher power,higher radiant energy,and multi-frequency composite beat operation.In this context,various multi-band microwave sources and multi-tube power synthesis technologies have been bom one after another,and the demand for multi-band mode converters has become increasingly urgentIn this paper,the combination of theoretical analysis,numerical calculation and simulation verification are used to study the mode coupling problem of circular waveguide and coaxial waveguide respectively.A high power mode converter with a coaxial embedded circular waveguide structure capable of operating in three frequency bands is proposed.The main work of this thesis includes the following aspects:Based on the coupled wave theory,the mode coupling problem in the over-modulus circular waveguide is studied,and the corresponding mathematical model is established.The coupled wave equations in the circular waveguide are deduced,and the coupling coefficients of each mode in the circular waveguide are given.Equation expression;The single-band ctrcular waveguide TM01-TE11 mode converter is analyzed and designed,and the feasibility of multi-band circular waveguide mode converter is discussed.The mode coupling problem in the coaxial waveguide with higher mode isolation is studied.The numerical optimization calculation program of coaxial waveguide is programmed,and the single-band TEM-TE11 coaxial waveguide mode converter with high conversion efficiency is designed-When the inner and outer radius ratio of the port is 2,the maximum conversion efficiency can reach 99,63%.The numerical solution program is further improved.The dual-frequency point iterative method is used to design the two-band mode converters that can work in X and Ku band,and the feasibility of multi-band coaxial waveguide mode converter is discussed.Based on the analysts of the internal mode coupling problem of circular waveguide and coaxial waveguide,a structure of coaxial embedded circular waveguide is proposed.The mode converter for three frequency bands of X,Ku and Ka can be used.The factors affecting the coupling ability between the modes are analyzed,and the optimization curve is obtained through the numerical calculation program.The actual model is built in the electromagnetic simulation software.The outer coaxial waveguide realizes the dual-band TEM-TEn mode conversion,and the inner circular waveguide realizes the single frequency band.The TM01-TE11 mode is changed,and the conversion efficiency at the center frequency of the three bands is higher than 97.88%.