| As a critical power amplifier in the field of vacuum electronics,the traveling wave tube(TWT)has such advantages as high output power,high gain and high efficiency.Nowadays its development is advancing towards miniaturization,high power and high frequency so as to promote the research on the wide-band terahertz radiation source with high power and efficiency,and the growth of high-performance equipment.However,there are still problems like higher ohmic loss and lower interaction impedance in the terahertz TWTs.To solve the existing problems,and shorten the interaction circuit length of the device and increase its power capacity,this dissertation tends to design novel slow wave structures(SWSs)of terahertz TWTs through an in-depth study of the high-power terahertz TWT,with the methods of theoretical analysis,simulating calculation and experiment research.The following is a summary of the main research contents and innovation points of the dissertation.1.A research on the staggered double vane(SDV)TWT enhanced by the 2π-mode interaction cavities: The design concept and scheme of the interaction circuit of the SDV TWT enhanced by the 2π-mode interaction cavities are put forward;its electromagnetic properties are analyzed to find out the influence of the cavities on the beam-wave interaction progress.For an electron beam with a voltage of 21 k V and an electric current of 200 m A,a maximum gain of 42.22 d B and an electronic efficiency of 4.47% have been achieved.Based on this,the fabricating progressing and experiment of the high-frequency system,and of the SDV SWS and the multigap resonant cavity are carried out and finished.The scheme of the SDV TWT enhanced by the 2π-mode interaction cavities is conducive to reducing the length of the interaction circuit,and improving the gain,the efficiency and the operating bandwidth of the circuit significantly.It provides a new idea for the minimization and integration of THz TWT.2.A research on the folded waveguide(FWG)TWT enhanced by 2π-mode interaction cavities: The design principle of the interaction circuit of the FWG TWT enhanced by 2π-mode interaction cavities is presented;the high-frequency characteristics of the FWG SWS is analyzed;and the theoretical research on multigap cavities is carried out.An overall design of high-frequency system of the FWG TWT is thus completed and the interaction circuit of the tube is presented.The total length of the interaction circuit is not more than 50 mm,the gain is 35.8 d B,the 3 d B bandwidth is 4.6 GHz,and the efficiency is 4.4%.This establishes an experimental foundation for the total tube,meets the requirements of the terahertz wave applications for wide frequency band,high gain and small size of the devices,and lays a theoretical foundation for the experimental study of G band FWG TWT enhanced by 2π-mode extended interaction.2.A folded waveguide(FWG)TWT,enhanced by 2π mode interaction cavities,is proposed.The design principle of the interaction circuit is presented.The high frequency characteristics of the FWG slow wave structure(SWS)is analyzed.The theoretical research on multigap cavities is carried out.The interaction circuit of this tube is presented,the total length of the interaction circuit is not more than 50 mm.The gain of the interaction circuit is 35.8 d B,the 3 d B bandwidth is 4.6 GHz,and the efficiency of the interaction circuit is 4.4%.It will build an experimental foundation for the total tube.It will meet the requirements of the terahertz wave applications for wide frequency band,high gain and small size of the devices.It will lay a theoretical foundation for the experimental study of G band FWG TWT enhanced by 2π-mode extended interaction.3.A research on the novel FWG TWT enhanced by π-mode extended interaction cavities: The design concept and scheme of the FWG TWT enhanced by the π-mode interaction cavities are put forward;the theoretical research on the unequal length slot interaction cavity is carried out;the stagger tuning technology is utilized to expand the operating bandwidth of the device;and the influence of the cavity loading on the performance of the interaction circuit is discussed and analyzed.The length of the interaction circuit is not more than 30 mm.The PIC simulation results show that the maximum average output power of the designed TWT amplifier is 65.78 W,which is corresponding to the maximum gain and efficiency of 37.38 d B and 3.9%,respectively.The per unit gain is 12.64 d B/cm and the 3 d B bandwidth is 3.5 GHz.The proposed FWG TWT enhanced by π-mode extended cavities maintains the high gain and the high efficiency operating performance.Simultaneously,it shortens the length of the interaction circuit,and promotes the development of miniaturization and integration of TWT.4.A research on the design and test of G band FWG TWT enhanced by 2π-mode interaction cavities: The simulating calculation of the beam-wave interaction process is done;the THz electronic optical system,matching the interaction circuit,is developed.The high-frequency system is fabricated and measured.The simulation results are in good agreement with cold-test experiment.The design,fabrication,and assembly processes of the tube is completed;the hot-test experiment is done.It provides a new programme of the reliable terahertz wave source for terahertz radar,communication,and imaging applications.5.A research on dual beam photonic crystal loaded FWG TWT: A novel dual beam overmoded FWG SWS loaded with photonic crystals is proposed;the electromagnetic properties are analyzed;the input/output coupling structure and the mode converter are designed.At the operating voltage of 21.2 k V,the operating current of 320 m A,and the input power is 50 m W,the proposed TWT can generate 128 W of output power at 220 GHz,corresponding to the gain of 34 d B,and its 3 d B bandwidth is 7 GHz.The wavelength is quite short at the terahertz band,and the dimension effect of the devices is obvious.The proposed overmoded FWG SWS can enlarge the size of the SWS,reduce the difficulty in possessing the high frequency circuit,and lower the negative effect of size in the terahertz band on the interaction circuit.The application of photonic crystal structure and the attenuator can prevent the leakage of the electromagnetic wave,suppress nonoperating mode and reduce the backward wave oscillations. |
