The Research Of650GHz Folded Waveguide Backward Wave Oscillator

The development of Terahertz spectrum has become the subject frontier and hottopic of electromagnetic field. With its unique properties, THz waves have thesignificant scientific value, and they have broad application prospects in the field ofmilitary equipment, scientific research, electronic information, information security,biological technology, national economy and other technical fields. THz devices havebecome a new challenge for vacuum electronics technology. Backward wave oscillatoras an important means of technology, can be used as a THz high power electromagneticradiation source.Backward wave oscillator is a relatively mature, miniaturization and low costvacuum electron source. It uses backward wave of the slow-wave structure to interactwith electron beam and generate microwave oscillations. It can be available forelectronic tuning in a very wide frequency range. As a very promising miniaturized THzsource, THz backward wave oscillator has a good feasibility. The thesis focuses onusing the folded waveguide as the slow-wave system, and designing the backward waveoscillator with a watt-magnitude power output signal at the650GHz band.This thesis does the detailed analysis for the backward wave oscillator on threeaspects, including the slow wave high-frequency characteristics of the folded waveguide,the transmission characteristics of the backward wave oscillator and beam waveinteraction characteristics. Folded waveguide slow-wave structure backward waveoscillator model is designed and calculated by the software, we obtain a larger signaloutput power and wide tuning bandwidth.The work and research contents of this paper are mainly listed as follows：1. This paper firstly studies the basic theory of the backward wave oscillator,introduces the current development, the main structure and main parameters of thebackward wave oscillator.2. The basic knowledge and high-frequency characteristic parameters of foldedwaveguide slow-wave structure is introduced. The design of the650GHz foldedwaveguide slow-wave structure model is finished by software with simulating and analyzing the impact of various structural dimensions on the folded waveguidedispersion and coupling impedance. Finally we obtain the best optimized size.3. It studies the impact of electron channel and the number of slow-wave cycle onthe transmission characteristics of the backward wave oscillator, finally we obtain thebest slow-wave system with40cycles by simulation.4. The650GHz backward wave oscillator output structure of pill-box windowmodel and attenuator model are designed to complete the whole650GHz foldedwaveguide slow-wave structure, and finished the simulation of beam-wave interactionby software. The folded waveguide slow-wave structure backward wave tube with sheetelectron beam can work from625GHz to675GHz, with a50GHz bandwidth and morethan1.2W output power; and the folded waveguide slow-wave structure backward wavetube with cylindrical electron beam can work from624GHz to669GHz, with a45GHzbandwidth and more than1.25W output power.