| The frequency of G band(170-260GHz)is located at the lower end of the terahertz frequency spectrum,which is an important atmospheric window.High-powe G-band traveling-wave tube has become one of the research hotspots.At present,the output power of the G-band driven source is too low to meet the requirement for the development of a 100-watt level traveling-wave tube.Harmonic traveling-wave amplifier is a potential,wide-band,high power terahertz source,which can be used as a solution for driven source of high power traveling-wave tube.The third-harmonic traveling-wave amplifier is selected as the research object,and the research is carried out from several aspects such as research background,slow-wave structure design,harmonic current analysis and beam-wave interaction.1.The terahertz wave and its applications are summarized and the development status of the terahertz radiation sources,especially the G-band traveling-wave tubes and high-harmonic traveling-wave amplifier,are given.2.The folded-wave guide slow wave structure with modified circular bends is briefly introduced,and the cold characteristic curve is analyzed and optimized.And the structure parameters of the fundamental-wave interaction section and the harmonic-wave interaction section are given.3.The main factors influencing on the harmonic current in the design process of the third-harmonic amplifier is studied and analyzed from five aspects of operating voltage,operating current,input power,sever starting position and sever length by CST PIC solver.The methods of increasing the maximum value of the third-harmonic current and reducing the interaction length are given.4.The G-band third-harmonic traveling-wave amplifier is simulated by MTSS software.Third-harmonic current at the end of the fundamental interaction section and saturation power at the end of the harmonic interaction section are optimized.A wide bandwidth of 15GHz and an output power over 3.6W are obtained.The single frequency performance,in-band performance and operation voltage are simulated and optimized by CST PIC.1W output power and 12GHz bandwidth are obtained.The results in this paper provide a solid foundation for development of G-band traveling-wave amplifier in the future. |
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