Design Of X Band High Power Microwave Transmission System

High power microwave?HPM?system can be disassembled into three parts.The first part is the microwave source,this part controls the performance of the whole system,its importance is comparable to the body of the heart;The second part is the microwave transmission,it is used as a bridge between the two parts,on the one hand,it restricts the performance of the first part,on the other hand,it provide feed for the third part,it also affects the size,the efficiency and output of the microwave mode of the whole system;The third part is the transmission and reception of microwave.The application of GW level high power microwave,first of all,the output power of microwave source must reach this level,and then it can maintain this level in the transmission process,while the former has been realized,so the problem to be solved is to ensure the efficient transmission of high power microwave.This dissertation focuses on how to suppress high order mode in the transmission process.The theoretical analysis,structural design and simulation study of the required coupler,the compact coaxial mode converter needed for mode conversion and the phase shifter needed for phase control are carried out for the high power microwave transmission system.The main contents are as follows:1.Based on the theory of pinhole coupling,the theory of phase superposition and the equidistance Chebyshev distribution,the sub-waveguides,hole spacings and hole sizes of the mode-selective directional coupler are determined.The relationship between the coupling hole thickness and the coupling degree as well as the influence of the coupling hole number on the performance of the coupler are studied by using the simulation.Finally,the specific structure of the X band TM₀₁ mode coupler is obtained,its directional performance is excellent and it can suppress both TM₀₁ and TE₁₁ modes simultaneously.The S band TM₀₁ mode coupler is designed and tested by the same method,and compared its cold test results and simulation results.2.The formula of correlation mode cut-off wavelength in coaxial waveguide is derived.According to the related parameters,the eigen equation curves corresponding to TM₀₁ mode and TE_n1 mode are plotted.The structure of the circular waveguide TM₀₁to circularly polarized coaxial TE₁₁ mode converter is proposed,which does not ues any media and can suppress high order mode in coaxial waveguide.The influence of different parameters on the conversion efficiency of the mode converter is studied by simulation.The output and input of the structure are coaxial,and the longitudinal length is about 3-4 wavelengths,which is more conductive to the compact design of a HPM radiation system and can work under over-mode state,and it also solves the problem that low power capacity of mode converter in high frequency band.3.According to the distribution characteristics of the electric field polarization directions of coaxial TE₃₁ mode and coaxial TE₁₁ mode,a coaxial TE₃₁ to coaxial TE₁₁mode converter structure is proposed.By changing the inner and outer radii of the coaxial waveguide at the output end,adding mode suppress rod,setting a taper gradient and other ways to suppress high-order mode transmission and reduce the reflection of coaxial TE₃₁ mode and coaxial TE₁₁ mode,which can improve the conversion efficiency of the converter.This method may also be suitable for converting coaxial TE₂₁ mode or coaxial TE₄₁ mode to coaxial TE₁₁ mode.4.The first time designed X-band HPM TEM mode phase shifter,its phase shift principle been verified by the theory and simulation.The phase shifter overcomes the limitation of power capacity in traditional phaser,which can be directly used to phase modulate and synthesize the output of TEM mode microwave.