Investigation On O-type Cerenkov Oscillator Operation At 60 GHz With High Efficiency And High Power Output

Due to the application requirements of directional energy,radar and electronic countermeasure,the development of millimeter wave sources becomes an important development trend of high power microwave?HPM?technology.And the invention of HPM source with high power output,high efficiency and miniaturization has become an urgent demand in the field of HPM,The method of theoretical calculation,electromagnetic simulation and particle simulation are combined in this paper in order to solve the technical problems of power capacity,mode control and high current electron beam transmission in high frequency band.Such investigation can explore the feasible technical route for HPM source to the development of higher frequency.The main works are as follows:First,the EH mode dispersion equation and the cold cavity characteristics of the infinite coaxial SWSs with arbitrary periodic boundaries are solved.Then the dispersion equation of radial infinite SWSs is solved,and the differences between axial and radial dispersion curves are compared.It draws the conclusion that the radial SWSs can not work in quasi-TEM mode.Second,the dispersion equation and the field distribution of coaxial SWSs with a finite thickness electron beam are calculated,and the computing method of the coupling impedance and the time growth rate are given.The dispersion characteristics,power capacity and coupling impedance of internal corrugation,external corrugation and dual corrugation of coaxial SWSs are compared and analyzed.The influences of the different corrugation positions and phase difference on high-frequency characteristics are discussed.The coulpling impedance of internal SWSs is higher,while the external corrugation has the higher power capacity.Third,a 57GHz overmoded relativistic backward wave oscillator?RBWO?operating on the quasi-TEM mode with high power,high efficiency and pure TM₀₁mode output is presented.Particle-in-cell simulation shows that generation with high power 560 MW and efficiency 43.5%is obtained under the diode voltage 520 kV and current 2.47 kA.And the microwave with the pure frequency spectrum of 56.8 GHz radiates in the pure TM₀₁ mode?about 98%?.Especially,the working mechanism of high efficiency and hign mode purity is elobrated theoretically.Fourth,a novel 60GHz RBWO operation at TM₀₂2 mode with large overmoded-ratio and the distance between inner and outer conductors slightly larger than?is proposed.The preliminary simulation results show the output power is 196MW and the efficiency is 21%.Its surface field strengh drops to 0.9 MV/cm,which has higher power capacity than that of quasi-TEM mode.