Multiphysics Analysis And Design Of High-power Microwave Circuits Based On COMSOL MULTIPHYSICS Analysis

With the rapid development of modern communication technology,high-performance microwave circuits are of increasing demand and the high-power microwave circuits have become an inevitable trend in the development of microwave applications.Unfortunately,when the microwave devices are working,some heat energy will be generated by the loss of devices,and thus the temperature of the circuit would be higher.This phenomenon has a bad impact on the transmission performance of the microwave circuit,and may cause serious faults of the whole system.Therefore,this problem should deserve great attention especially in high-power microwave circuits.To solve this problem,multi-physics analysis of circuits,especially thermal analysis is essential during the design processing of microwave circuits,which also provide helpful guidance for the high-power circuit design.Based on the simulation software COMSOL MULTIPHYSICS,the thermal analysis of microwave transmission lines and some high-power microwave circuits are carried out in our work.Moreover,two high-power microwave power combiners are also designed and verified experimentally.The main contents of this thesis can be summarized as:1.Theoretical analysis of electromagnetic field and microwave device based on the finite element analysis method: On the basis of the simulation software COMSOL MULTIPHYSICS,detailed analysis of finite element analysis method in multi-physics is launched.Then,the above analysis is applied to the electromagnetic field for solving the simulation problems in the frequency domain.In addition,the multi-physics analysis,especially thermal analysis,is also applied to the microwave devices.These works provide some useful theoretical guidance for thermal analysis of high power microwave circuits.2.Applications of multi-physics analysis in transmission line: On the basis of transmission line theory,the microstrip line and substrate integrated waveguide are investigated and their theoretical power capacity are derived.Moreover,the microstrip line and substrate integrated waveguide are respectively modeled and simulated by the simulation software COMSOL MULTIPHYSICS,and their thermal analysis are also performed to obtain the true power capacity.These work validate the effectiveness of multi-physics analysis and provide a method for power capacity analysis in high power microwave circuits.3.On-board high-power microwave power synthesizer based on multi-physics analysis: For spaceborne applications,a high-power four-way power synthesizer is designed based on the multi-physics analysis,which is designed by stripline.By simulation,it can befound that the peak power of the on-board power synthesizer can reach 295 KW,and the average power capacity can reach 43 KW,which satisfies the high power requirement of special space environment.4.High-power broadband VHF two-way power synthesizer based on multi-physics analysis: For solid-state transmitters applications,a high-power wideband VHF two-way power combiner is designed based on the multi-physics analysis.The proposed power combiner is realized by combining the primary and secondary circuits together,and realizes good performances including a large bandwidth,high isolation and high power resistance.Specially,the primary circuit is implemented by stripline,and the secondary circuit of the secondary circuit is realized by microstrip line.Besides,the primary and secondary circuits are connected with each other vertically by the coupling line and then good transmission and high isolation can be obtained.By simulation,it can be found that the high-power broadband VHF power combiner can achieve a high peak power of 450 KW and an average power capacity of 30 KW.