Research On Sine Waveguide Traveling Wave Tube

Terahertz technology has great scientific value and development prospects in basic research fields such as physics,chemistry,astronomy,and radar guidance,electronic countermeasures,and space communications.Traveling wave tube(TWT)is an effective device to obtain terahertz wave.As the core component of the TWT,the slow-wave structure(SWS)plays a decisive role in the performance of the device.However,as the frequency increases,the SWS encounters technical problems such as low coupling impedance,and large transmission loss.The flat-roofed sine waveguide slow-wave structure is a slow-wave structure suitable for working at the terahertz frequency band.It has the characteristics of wide working bandwidth,low transmission loss,and small reflection.It is considered as a potential slow-wave structure in the terahertz frequency band.In this paper,a series of the flat-roofed sine waveguides SWS working in the terahertz frequency band are carried out.The main contents of the work are as follows:1.Theoretical design of a 220 GHz flat-roofed sine-waveguide TWT has been carried out.The transmission characteristics show that the flat-roofed sine-waveguide SWS has very small reflection and low transmission loss.Beam-wave interaction results show,that a peak power of more than 100 W can be obtained in the frequency range of212GHz-224 GHz,the highest output power can reach 124 W.the electronic efficiency is greater than 4.6%,and the 3d B bandwidth is greater than 15 GHz.What's more,the electronic optical system of the 220 GHz flat-roofed sine waveguide TWT has been designed,and a PCM magnetic focusing system with a transmission rate of 100% has been obtained.Finally,the 220 GHz flat-roofed sine waveguide SWS and energy transmission device has been experimentally processed and tested.2.The non-convergence scheme of 220 GHz flat-roofed TWT has been designed,including the SWS and the input/output structure.The transmission characteristic result shows that the reflection coefficient S11 is blow-15 d B in the range of 212GHz-230 GHz,the transmission coefficient S21 is greater than-0.12 d B,and the transmission coefficient from input port to the beam channel port S31 is lower than-35 d B in the range of212GHz-230 GHz.This shows that the SWS with input and output structure has a good transmission characteristics,and at the same time has a good electromagnetic isolation with the electronic optical system.Beam-wave interaction results show that in the range of 213GHz-221 GHz,the TWT can produce an output power of more than 6W,and the maximum output power of 13.7W at 217 GHz.3.The study on flat-roofed quasi-sine waveguide SWS has been carried out.Considering that in the terahertz frequency band,the flat-roofed sine waveguide SWS is not easy to be processed due to the small radius of curvature.The author's team modified the conventional flat-roofed sine waveguide SWS and proposed a flat-roofed quasi-sine waveguide SWS which can be easier processed in the terahertz frequency range,and its high-frequency,transmission and beam-wave interaction characteristics have been simulated.What' more,the designed SWS has been processed and cold-tested.The cold-test results show that the flat-roofed quasi-sine SWS has good performance on transmission characteristics,and the experimental results are in good agreement with the simulation result.4.The 340 GHz circular beam sine waveguide TWT hae been designed.The high-frequency simulation shows that the result of reflection coefficient S11?-30 d B and the transmission coefficient S21?-5.82 d B in the frequency range of 320-360 GHz.The results show that the 340 GHz circular beam sine waveguide TWT has has low return loss and insertion loss.The Beam-wave interaction has been simulated,whose results show that the TWT can produce a output power more than 2.8W in the frequency range of 325GHz-350 GHz.Finally,the pill-box window of the 340 GHz circular-beam sine waveguide TWT has been designed.The simulation results show that the return loss S11 is blow-25 d B,and the insertion loss S21 is higher than-0.28 d B in the range of 330GHz-350 GHz.