Investigation Of High Efficiency Q-band Folded Waveguide Traveling-wave Tube

In TWTs, the research focus has been on coupled cavity traveling wave tubes and the helix TWTs. Coupling impedance and out power of Coupled cavity traveling wave tubes is high, but bandwidth has always been a problem; the bandwidth of the helix TWTs is wide, but the cooling and power is not very ideal. In order to counteract these disadvantages of traveling wave tube devices, in recent years, a new kind of slow-wave structure more and more get the attention of the researchers—folded waveguide traveling wave tube. This new type of slow-wave structure has been made of metal structure, so it is good at heat dissipation and with high coupling impedance, also it is simple to process. With the constant improvement of the working frequency, the advantage of the folded waveguide TWTs is more and more obvious. It has great competitiveness in the millimeter wave and submillimeter wave devices. Q band folded waveguide TWTs have a wide range of applications in satellite communications, radar and etc with its frequency band edge. We design a folded waveguide TWTs in 43.5~45.5GHz after a simple introduction of the history, the research significance and current situation. The electronic efficiency of the tube reach 7%, the output power is above 150 W, and the whole tube average gain more than 40 dB. Then we introduce the phase velocity taper technology what makes the efficiency increase by about 7% The research content includes:1. Folded waveguide slow-wave structure. We have made a theoretical analysis in the equivalent circuit model of the folded waveguide slow-wave structure. Then we have made a analysis in the nonlinear large signal theory, and complete the one-dimensional nonlinear large signal simulation work with MATLAB reference for the further optimization. We complete the simulation and optimization of the slow-wave structure’s cold parameters with HFSS, and made detail analysis in the influence of each dimension parameters. Finally we simulate a interaction parameters with TAU which meets the design requirements.2. Periodic permanent magnetic focusing system(PPM), input output structure and attenuator. For the slow-wave structure, we design a PPM through theoretical calculation, the come up with a PPM which reaches the design requirements after the simulation with FEMM. We adopt a hyperbolic arc gradient structure after in the reference of researchers of the technology electric vacuum laboratory at UESTC. The reflection is very small from the results. Attenuator is used for carburizing beryllium oxide material E surface wedge gradient deformation structure which meets the design requirements after the help of above researchers.3. Phase velocity taper. In order to improve the efficiency and output power, we use the phase velocity taper technology which cuts the tube in three pieces on the basis of the previous design. It has been a certain effect, but it remains to be further research for the result point of view.