Study On Novel Sine Waveguide SWSs And Devices Based Upon The SWSs In The Terahetz Band

Terahertz science and technology is a research hotspot in the field of electronic science and technology,and it is extremely important in many aspects of broadband communications,biomedical imaging,safety inspection and nondestructive testing applications.One of the key problems in the development of terahertz science and technology is how to produce the terahertz wave,and the vacuum electronic devices could be considered as the important measure to develop the terahertz radiation source.Of all the Vacuum electronic devices,the traveling-wave tube(TWT)and backward wave oscillator(BWO)are widely used as the high power radiation source.However,the slow wave structure(SWS)which is the core component of the devices has the low coupling impedance,strong reflection and high transmission loss.In order to solve these problems,the author achieves a breakthrough by the innovation of the SWS.In this paper,four novel SWSs including ridge loaded sine waveguide(RLSWG),truncated sine waveguide(TSWG),slotted sine waveguide(SSWG),and sine shape ridge waveguide(SSRWG)have been proposed.After analysis,we find that four novel SWSs partly solve the problems of low coupling impedance,strong reflection and high transmission loss.Therefore,the author combines the their respective strengths of each structure and applying them to the appropriate device design.Thus,the performance of the existing high power terahertz radiation source will be effectively improved.The author does a thorough analysis for the novel SWSs on three aspects,including slow wave charateristics,transmission properties,and beam-wave interaction charateristics.Then,we apply these SWSs in the design of terahertz TWT and BWO based on their characteristics.The main innovation of this thesis include:1.Proposed a ridge loaded sine waveguide(RLSWG)SWS which is suitable for the pencil electron beam devices,and the SWS has large coupling impedance,weak reflection,and low transmission loss.Meanwhile,we build the high frequency system of G-band RLSWG TWT,and we complete the optimization design of the high frequency system.The calculation results indicate that the RLSWG TWT has the larger output power and the shorter interaction length.In the G-band,the maximum output power increases by 14.3%,and the interaction length is shortened by 9.6%.2.Proposed a truncated sine waveguide(TSWG)which is suitable for the sheet electron beam device,and the SWS has wide bandwidth,large coupling impedance,weak reflection,and low transmission loss.The beam-wave interaction calculation results indicate that the TSWG TWT has the larger output power and the shorter interaction length.In the G-band,the maximum output power increases by 15.1%,and the interaction length is shortened by 16%.Meanwhile,we proposed a design scheme of the high frequency system of the G-band TSWG TWT.The simulation results show that the TWT can produce the output power of over 57.5W and the gain of over 30.6d B in the frequency range of 210~255GHz under a beam voltage of 20.8kV and a beam current of 100 mA.Besides,the maximum output power achieves 115 W and the 3d B bandwidth exceeds 45 GHz.3.Proposed a slotted sine waveguide(SSWG)which can be used for the pencil electron beam BWO,and the SWS has very large coupling impedance and low transmission loss.Meanwhile,we have designed a novel SSWG reflector and applied it in the design of 380 GHz SSWG BWO.The simulation results indicate that the BWO can generate over 8.05 W output power from 363.4GHz to 383.8GHz by using a 30 mA pencil electron beam and adjusting the beam voltage from 20 kV to 32 kV.4.Proposed a sine shape ridge waveguide(SSRWG)which combines the advantages of the sine waveguide and the double ridge waveguide,and the SWS has wide bandwidth,large coupling impedance,and low transmission loss.The simulation results show that the SSRWG BWO possesses the larger output power than the sine waveguide BWO in the frequency range of 0.6~1THz.In addition,the tunable bandwidth of BWO is broadened by 13.2%.Build the high frequency system of G-band SSRWG BWO,and the system includes the SSRWG SWS,output coupler,match termination,converter and so on.The simulation results demonstrate that the SSRWG BWO can generate over 0.99 W output power in the frequency range of 175.2~251.9GHz by using an 11 mA sheet electron beam and adjusting the beam voltage from 6kV to 18 kV.5.Design the experimental test model of the W-band SSRWG SWS,and we have completed the machining of the model and testing of transmission properties.The experimental results show that the transmission parameter is more than-3.65 dB and the reflection parameter is less than-15 dB except the frequency point of 80.5GHz in the frequency range of 75~110GHz,which indicates that the SSRWG SWS owns the good transmission properties within a wide frequency band.In summary,the studies on four novel SWSs and the designs for the corresponding devices are very significant for the development of the terahertz TWT and BWO,especially provide a variety of new approaches for the research of the high power terahetz radiation source.