Design Of Mode Conversion Link Based On External Gyrotron

In the modern millimeter wave communication,phased array radar and satellite broadcasting wireless communication system,in order to transmit and measure the high power microwave,the high efficiency mode converter plays an important role.Therefore,the design of mode converter has attracted much attention.This paper will design two kinds of mode converters.The whole thesis contains the following aspects:1.First of all illustrate the theory,the coupled wave equations will be derived from coupled transmission equations,the coupled wave equations will form orthogonal function expansion theory.Then,a simplified theoretical analysis of the circular waveguide with axis bending is adopted,and the expressions of output power,the coupling coefficient and coupling critical angle between two different modes are derived.As for the single stage abrupt structure and the two stages abrupt structure waveguide,the scattering matrix can be derived from the equation.2.Based on the coupling wave theory of circular waveguide with axis bending and mode matching method of abrupt structure circular waveguide,the third chapter adopted the software MATLAB to write the related numerical calculation program and the optimized parameters of the mode converter waveguide can be obtained.First,a circular waveguide TE₀₁-HE₁₁ mode converter at 24.13 GHz was designed.The mode converter system mainly consist three parts: a TE₀₁-TE₀₁ transition device,the TE₀₁-TE₁₁ and TE₁₁-HE₁₁ circular mode converter.The model was simulated and verified by the Commercial Microwave Studio CST Software,and the actual object was processed.The measured results shows that the bandwidth of the mode converter systems is 5%,and the transition efficiency exceed 99% in all over band.The results of calculation,simulation and measurement are consistent.3.The over mode circular waveguide with axis bending mode converter is a very complicated device.According to the characteristics of high power over mode output for the gyro traveling wave tube,the output power of TE0 n mode is about 100-200 kW.In the fourth chapter we design a high power circular waveguide TE₀₁-HE₁₁ mode converter with axis bending,and the TM11 mode act as intermediate model.First,we introduced the TE₀₁ mode right-angle waveguide with axis bending,then,the TE₀₁-TM11 mode converter with axis sinusoidal bending structure and the TM11-HE₁₁ mode converter with circumferentially corrugated waveguide are designed and illustrated,respectively.The transition efficiency is above 99% from 33 GHz to 37 GHz.Good performance can be achieved.At last,we analyzed the power capacity.Finally,we conclude the achievement of this thesis,propose several method of improvement and predict the work in the future.