Theoretical Research For Extended Interaction Device On Millimeter Wave Band

Extended interaction device has the characteristics such as small size, light weight and compact structure, it could achieve high power output in the millimeter-wave and terahertz frequencies and has significant features and advantages with respect to the klystron, traveling wave tube, gyrotron and other devices. The study for extended interaction device has important significance for the development of millimeter wave and terahertz technology. At present, the research of vacuum devices for microwave and millimeter wave was most focused on the aspects such as the klystron, traveling wave tube and gyrotron. But the research work was not enough in terms of extended interaction device, so there is a big lack.Based on the kinematic theory, we have studied and analyzed the physical process of the extended interaction devices, the characteristics of the extended interaction cavity such as the coupling coefficient and the electron conductance in this paper. We have also analyzed the advantages of extended interaction structure for high frequency applications. Extended interaction cavity has characteristics both of resonator and slow-wave line, increasing the characteristic impedance and coupling coefficient, it improves the interaction efficiency and increases the power capacity. The electron beam could be effectively modulated in the extended interaction structure and the length of the drift section has been significantly shortened, so the extended interaction devices could be designed with a compact structure.Computer simulation for vacuum devices has played an increasingly important role in the design process, and there is a variety of simulation software at home and abroad. But the calculation by simulation software usually takes tens, hundreds of hours, which is still a great restriction to the research and design of extended interaction devices. Based on the one-dimensional electron model, a nonlinear theoretical method by using C++ programming language has been used for simulating the beam-wave interaction process of extended interaction oscillator and extended interaction amplifier in this paper. By importing the electric field distributing form the cold cavity electromagnetic simulation software, the theoretical method could quickly give the calculation results with great reference value. In the same computer condition, the nonlinear method only needs thousandth time of that which is needed in the calculation of electromagnetic simulation software. Combined with electromagnetic simulation software, the non-linear programming could significantly shorten the design and development time, and it has great value in the parameter design and optimization process.The extended interaction oscillators and extended interaction amplifiers in 35 GHz and 220 GHz frequencies with rectangular configuration structure have been studied and designed in this paper, and the using process of the theoretical method has been described in detail. At the same time, we have compared the extended devices with different number of the gaps. Combined with small signal theory, nonlinear simulation program, PIC simulation software verification, a complete analysis theory and design process for extended interaction devices has been presented in this paper.A new radial extended interaction structure has been proposed in this paper. Compared with the traditional extended structure, the radial extended interaction device significantly increases the operating current by expanding the cathode electron emission area, and this new structure would have great research value and good prospects in high power output applications. The theory analysis, non-linear calculation and PIC simulation for verification have been carried out in the research work of the radial extended oscillator. In the same time, the electron-optical system of the radial interaction structure has also been designed to prove the feasibility of this new structure.