Phase Control And Power Measurement In Oversized Waveguide System

High-power millimeter（HPM）wave favors widespread application in telecommunication,high resolution radar imaging,microwave weapons,and so on.Gyrotron traveling wave tube（Gyro-TWT）,which features broadband and hundreds of kilowatts high power,has attracted extensive concern.Different modes are adapted depending on different operating conditions.Based on the application of HPM oversized waveguide system,the researches for circular polarizer and directional coupler are conducted.Details are as follow:1.For the gyro-TWT with TE₀₁ output mode,the research of multimode power measurement coupler is carried out.In Ka-band,gyro-TWT always employs TE₀₁ mode in circular waveguide since it features low loss in long way transmission.However,the parasitic circular TE₀₂ mode is easily excited due to the high operating frequency.In this thesis,a dual mode power measurement method is introduced for operating and parasitic mode.The boundary conditions are change by waveguide perturbation to enlarge the field difference of TE₀₁ mode and TE₀₂ mode.According to the field distributions of TE₀₁ mode and TE₀₂ mode,the couplings are placed at different position to design coupler,realizing the measurement for dual mode.Simulation and experiment demonstrate that the coupler is able to measure the powers of TE₀₁ mode and TE₀₂ mode from 30 GHz to 40 GHz.The coupling coefficient is-40 d B and the directivity is better than 20 d B.The mode selectivity for both modes are 15 d B and 20 d B,respectively.2.The technique of high-power broadband circular polarizer is introduced for gyro-TWT with TE₁₁ output mode.Gyro-TWT operating in X band always employs circular polarization TE₁₁ mode in circular waveguide.Such an output field distribution is not conductive to the design of subsequent HPM components.A combination method of multi dispersion is proposed in this thesis.By the superposition of multi dispersion characteristics,the broadband phase control is realized.Base on the method,a broadband circular polarizer operating in X-band is proposed.Such a circular polarizer achieves the transformation between circular and linear polarization from 7 GHz-10 GHz with 90±3°phase difference and 1.1 axial ratio.