Research On Applying Optimization Algorithm To Traveling Wave Tube Design

Traveling wave tube(TWT)is a microwave electric vacuum device that can amplify microwave,millimeter wave and terahertz signals.It has outstanding advantages such as high output power,wide frequency bandwidth,and strong environmental adaptability.It is widely used in aerospace,electronic countermeasures,radar,etc.The theoretical basis of TWT is complex,and there are numerous indicators to satisfy while designing TWT,which makes it tough to find a set of parameters that improve the overall performance of TWT.At present,the design optimization of TWT highly depends on the designer.With the increasingly stringent performance requirements on TWT,the manual tuning method that based on the designer's experience,is gradually unable to meet the needs of the development of TWT.In this thesis,we take the TWT design tuning problem as the research object,implement a TWT simulation design optimization tool that based on the fast non-dominated genetic algorithm(NSGA-?)and the Mirocwave Tube Simulator suite(MTSS).Our optimization tool takes into account multiple indicators to find out a set of dimensions parameters that improve the overall performance of TWT.The main work of this thesis is as follows:1.Study the NSGA-? in-depth.Analyze the fast non-dominated sorting algorithm and genetic algorithm,the core of NSGA-?.Discuss crowding distance sorting algorithm and elite strategy,which affect the convergence process and the optimal solution.Compute the time complexity of each part of NSGA-?,constructe a full understanding of the optimization process.2.Design and implement a TWT simulation design optimization tool that based on NSGA-? and MTSS.Propose dynamic workflow mechanism that automatically handles the dependencies in the simulation process and builds a parallel workflow? improve computational resources utilization by using thread pool,which greatly improves the efficiency of optimization tools? encapsulate the communication process between algorithm and MTSS,which greatly simplifies the conversion process between the TWT design and the optimization algorithm parameters? implement the user interface of the optimization tool,which supports load MTSS project,set up simulation process,update optimization progress and display the optimization results.Our optimization tool provides an efficient solution for solving the parameter optimization problem while designing TWT.3.Optimize the pitch distribution design of the helix TWT with our traveling wave tube simulation design optimization tool.Improve the output power,gain and electronic efficiency while suppressing the abnormal phase shift.The optimization result shows that the electronic efficiency of the working frequency band is not less than 19.62 percentage and the nonlinear phase shift does not exceed 45 degrees,which verifies the correctness of the optimization tool? on the basis of the above,we select in-band power flatness as the fifth optimize goal.Compare with the original design,the electronic efficiency of the working frequency band is not lower than 19.38 percentage,the saturated output power at the intermediate frequency point is increased by 13.25 W,the in-band power flatness reduce to 13.72 W and the nonlinear phase shift is 37.56 degrees,which verifies the correctness of our optimization tool again.