Study Of The Terahertz EIA Based On Subwavelength Hole Array Composite Structure

With the continuous development and application of terahertz technology,there is an urgent need for terahertz radiation sources with better performance indicators.Compared with solid-state devices,vacuum electron radiation source devices are an effective way to promote better applications of terahertz technology.The extended interaction klystron amplifier combines the advantages of klystron and traveling wave tube.With its unique advantage of multi-gap cavity,it can achieve high power,high gain and wide bandwidth.It has always been a research hotspot in the field of terahertz vacuum electronic devices.In this thesis,a composite structure combining the traditional ladder-shaped line and trapezoidal subwavelength hole arrays is used as a high-frequency system to design an extended interaction amplifier(EIA)in the terahertz frequency band.The specific work is as follows:(1)The electromagnetic properties of the EIA high-frequency system combined with the ladder-shaped line and subwavelength holes are studied.The simulation finds that the characteristic impedance is optimal when the long base of the trapezoidal subwavelength hole is proportional to the broad side of the resonator;by analyzing the electric field distribution characteristics of a single-period trapezoidal subwavelength hole resonator with equal proportions of long bottom and broad sides,TM₃₁-2?is selected as the working mode;simulation and analysis of the effects of structural parameters such as subwavelength holes and resonators on dispersion and coupling characteristics;the mode competition problem in the EIA with a 5-gap intermediate cavity,and the terahertz wave coupling characteristics of the rectangular and trapezoidal subwavelength holes in the TM₃₁-2?mode are studied.(2)Combining the advantages of traveling wave tubes,a new high-frequency structure is proposed,which is a strip-injected ladder-shaped line-rectangular subwavelength hole coupled cavity chain.Preliminary research shows that the characteristic impedance and mode frequency interval of this structure are large,and it is expected to achieve higher gain and a wider frequency band.(3)A composite EIA 3D model with rectangular sub-wavelength holes as input and output cavity and trapezoidal sub-wavelength holes as intermediate cavity is established and PIC simulation is carried out.The EIA adopts a five-cavity structure,and the working parameters,staggered tuning parameters,and drift tube length are analyzed and selected.The EIA output performances are obtained through PIC simulation:when the input signal frequency is 230.82GHz,the output power is 75W,the gain is 35.74d B,and the-3d B bandwidth is 850MHz.The main factors affecting the bandwidth are analyzed,and the optimization ideas of increasing the number of intermediate cavities,changing the staggered tuning parameters and using trapezoidal subwavelength holes for input and output cavities are proposed.(4)The performance of the terahertz EIA is optimized by simulation.When the EIA input and output cavity still use rectangular subwavelength holes,the middle three cavities are increased to four cavities,and through staggered tuning,the output performances of the EIA are obtained by simulation:when the input signal frequency is230.92GHz,the output power is 104.42W,and the gain is 37.17d B,the-3d B bandwidth is close to 1.1GHz,and the efficiency is 2.38%.When the input and output cavity adopts trapezoidal subwavelength holes,the middle cavity is kept as three cavities,and by optimizing the staggered tuning parameters,the simulation results of EIA are obtained:when the input signal frequency is 230.6GHz,the output power is 123.93W,and the gain is 37.92d B,the-3d B bandwidth exceeds 1.1GHz with an efficiency of 2.81%.Although both structures have obtained higher gain and wider bandwidth,the performance of the EIA whose input and output cavity are a trapezoidal subwavelength hole structure is slightly higher than that of the rectangular subwavelength hole structure.