Reseach On Marching-on In-time Scheme And The Fast Algorithm Of Time Domain Integral Equation

Millimeter wave is the frequency range from 30 to 300 GHz.It has the characteristics of shorter wavelength and larger bandwidth.In recent years,because of deficiency of spectrum resource,many countries are developing higher frequency resource.Therefore,the millimeter wave has been very popular and all kinds of millimeter wave devices have been invented.Compare with other relative devices,the traveling wave tube is studied insufficiency,but it has the characteristic s of large bandwidth and high power,which can meet the demand of modern military and civilian.Therefore,millimeter wave gyrotron traveling wave amplifier has become a research hotspot.As the working frequency of electronic vacuum devices increasing,a series of problems is emerging to constrain the development of device,such as smaller electrical size.Due to the higher operating frequency imply the smaller device size,which leads to the smaller power capacity of the device,as well as the difficulty of manufacturing.In order to solve the problem of power capacity,usually adopt the high order mode as the working mode of the device.But this can lead to severe mode competition,which makes it difficult to get stable output.This is also the main factor restricting the development of millimeter wave gyrotron traveling wave tube.To make the traveling wave tube in a stable state,scientists have proposed some ways to restrain mode competition.For example,in the conventional circular waveguide,the atte nuation material is used to suppress the mode competition,but there are some problems such as processing and heat dissipation.Fortunately,using confocal waveguide structure and particularity of photonic crystals to suppress the mode competition,it is a kind of open interaction cavity,which can be used to restrain the mode competition through the diffraction loss on both sides.Gyrotron traveling wave tube(TWT)is a high power electronic vacuum device based on electron cyclotron maser effect,the amplification of electromagnetic wave is in the interaction cavity.In this paper,the confocal waveguide is used as the interaction cavity of gyrotron traveling wave tube,the structural design,distribution of the Gauss field,diffraction loss,mode competition,absolute instability and the backward wave oscillation of the confocal waveguide is present.Specific work is as follows:1.The reason suppressing the development of millimeter wave gyrotron traveling wave tube is analyzed.According to the working principle of the gyrotron traveling wave tube,the Gauss beam in the confocal waveguide is studied,and the electromagnetic field distribution equation of the Gauss beam is deduced;Structural design and mode selectivity of co nfocal waveguide is studied;The stability of the gyrotron traveling wave tube is analyzed,and the calculation formula of the starting current and the method of back wave suppression are given.Lay the foundation for the research and Simulation of the gyrotron traveling wave tube.2.Design the 140 GHz confocal waveguide gyrotron traveling wave amplifier.The stability and the characteristics of backward wave oscillation are studied,and the structure of suppressing the backward wave oscillation is designed.The stable output power is 140 k W by optimizing the electrical parameters and structural parameters.The output peak power is 6.87 kw,the efficiency is 9.03%,the gain is 28.3d B,the 1d B bandwidth is 2.3GHz.3.Based the content above,design the 220 GHz confocal waveguide gyrotron traveling wave amplifier.Specially,the starting current and method of suppressing the backward wave oscillation are analyzed.The particle simulation software is used to optimize the structure parameters and working parameters.At last,a 220 GHz confocal waveguide gyro traveling wave amplifier with stable output is obtained.