Research On The Design And Efficient Optimization Method Of A New Staggered Double-gate Slow-wave Structur

With the development of microelectronics technology,solid state circuits have gradually replaced traveling wave tubes(TWTs)in low frequency and low power applications.However,in the sub-THz band,TWTs are still widely used because of its high output power and high efficiency.Slow wave structure(SWS)is a key component in TWT.The double-staggered grating waveguide(DSGW)is an all-metal SWS,which has advantages such as high operating bandwidth,high power capacity,easy processing,and natural banded electron beam channels,and is suitable for sub-THz TWTs.However,the interaction impedance of the DSGW is low,which affects the output power and gain of the TWT.In addition,there is still a lack of efficient optimization methods for this SWS.In this paper,a modified DSGW is designed to solve these problems,which can obtain higher output power and gain.TWT based on the modified DSGW can achieve higher output power and gain.At the same time,two different optimization methods based on surrogate model are proposed to optimize the cold-test performance of the SWS.The specific contents of this article are as follows:Firstly,a modified DSGW SWS is proposed,and the influence of size parameters on its interaction impedance and dispersion characteristics is analyzed.The results show that the modified DSGW has higher interaction impedance and lower dispersion characteristics compared to the DSGW.In addition,the beam-wave interaction characteristics of this structure in sub-THz TWT were studied.The TWT based on the modified DSGW can achieve a saturated output power of 116.64 W at 20.4 k V electron voltage and 0.1 A electron current,with a corresponding saturation gain of 15.9 d B.Secondly,a SWS optimization method based on the surrogate model and improved adaptive penalty function is proposed.During the optimization process of the SWS,this method imposes penalties on individuals who violate the phase velocity and dispersion characteristics constraints,thereby obtaining the SWS with similar phase velocity,good dispersion characteristics,and high interaction impedance.To verify the effectiveness of this method,it was applied to the optimization design of helix SWS,T-shape Staggered Double-Vane(T-SDV)and the modified DSGW.Under the condition that the phase velocity and dispersion characteristics meet the constraints,the interaction impedance of the three SWSs were increased by 32.3%,39%,and 42.8%,respectively.The results show that this method has achieved good implementation.Finally,an improved SWS optimization method based on non-dominated sorting differential evolution(NSDE)algorithm is proposed.This method uses the Pareto dominance rule to rank individuals,thereby solving the problem of multi-objective optimization of cold test parameters for the SWS.As a verification,it was applied to the optimization of T-SDV,folded waveguide(FWG),and the modified DSGW,respectively.Under the premise of similar phase velocities and lower dispersion characteristics,the interaction impedance of the three SWSs were increased by 30.8%,18.3%,and 66.2%,respectively.This shows that the method has achieved significant results.