Research On High-frequency Structure Of W-band Confocal Waveguide Gyro-TWT

In the high energy weapons, space exploration, radar tracking, electronic countermeasures and the weather forecast field has very important application of millimeter wave technology. As the emphasis a difficult point of millimeter wave technology, so the research of millimeter wave source is very important. The gyro-TWT is a kind of vacuum electron devices based on electron cyclotron maser, because of its high-power, wide-band and high-efficient output character in millimeter and even terahertz frequency range, gyro-TWT has become research hot spot at home and abroad. But with the increase of frequency, the modes competition of the gyro-TWT is becoming more and more prominent, so the interaction structures with mode selection characteristics will stand out. Confocal waveguide is a structure with lateral opening, so that the electromagnetic wave can be diffracted out from lateral open surface. This character can be used to solve the mode competition problem.The theme of this dissertation is RF structure of W-band confocal waveguide gyro-TWT. After compromise the capacity of power and mode competition, choose the working mode of HE06. Based on the linear theory of gyro-TWT, the dispersion characteristics and diffraction loss of a W-band gyro-TWT using confocal waveguide were calculated and simulated, at the same time, the mode competition issues are analyzed.The input coupling system of confocal waveguide gyro-TWT has be researched in the theme. Based on the traditional single –ended input vertical coupling system and double side vertical symmetric input coupling system, a tilting symmetric input method is proposed to expand the bandwidth of the input coupling system. At the same time, the method was proposed to suppress the coupling to competition mode by changing the boundary conditions. At the last, the simulation and optimization to the input system of confocal waveguide, the performance of the input coupling system: the maximum coupling efficiency is 75.68%, the 3dB bandwidth is 8.2 GHz, the relative bandwidth is 8.41%, the bandwidth is 6.8 GHz of coupling efficiency more than 60%.At the last, based on the nonlinear theory of gyro-TWT, the beam-wave interaction mechanism of gyro-TWT was analyzed. The PIC simulation to confocal waveguide with the working mode is HE06, found that the mode competition problem is very serious, which leads to the work mode HE06 cannot be efficient and stable amplification. From the viewpoint of reducing competition pattern, and in order to eliminate the problem caused by input coupler, design the confocal waveguide with the work mode is HE04, By way of its direct input of the PIC simulation calculation and optimization, get the stability of 200 kW output power, the maximum output power is 204 kW.