Investigation On A V-band Transit-time Oscillator

Transit-time oscillator is attractive for its stability,high output power,simple structure and single-moded operation.After introducing the coaxial structure,the power capacity of the device can be improved by increasing the radius of the inner and outer conductor in an equal distance.Therefore transit-time oscillator has the potential of high frequency operation.More and more attention has been paid to V-band electromagnetic radiation due to its increasingly wide military and civil application.Based on the discussion above,A V-band transit-time oscillator is proposed and related research is carried out in this dissertation.Firstly,the V-band transit-time oscillator is investigated theoretically.Linear theory and nonlinear theory are compared by 3?/4 mode of TM₀₁ mode.Nonlinear theory is more precise than linear theory but the design of the V-band transit-time oscillator can still be precisely analyzed by linear theory.Secondly,we study the eigen modes of the buncher cavity of the V-band transit-time oscillator.Through linear theory,the operating voltage ranges of the eigen modes are calculated and the operating modes under voltage of 520kV are investigated.Compared with four-gap buncher,the mode separation of five-gap buncher is less obvious and the single-moded operating voltage range is narrower,but the efficiency of beam wave interaction is higher.Based on theoretical analysis and numerical calculation,the V-band transit-time oscillator is investigated by PIC simulation.In PIC simulation,the output microwave of760MW,70.40GHz is obtained under the condition of 520kV,9.21kA and guiding magnetic field of 1.8T.The operating mode and structure parameters are very similar to the results of theoretical analysis and numerical calculation.Finally,as the base of experiment research,related engineering design of V-band transit-time oscillator is carried out,including the design of the guiding magnetic field,the design of supporting rods and the design of coaxial mode converter.The structure was optimized by simulation software.In the magnetic field design,the 1.8T magnetic field can be guaranteed on the transport path of the electron beam.In the design of supporting bars and mode converter.Efficiency of microwave transmission can sustain a high level.