Mechanism Study Of Novel Millimeter-wave EIA Devices

In order to promote the development of millimeter-wave technology,we need a stable millimeter-wave-terahertz radiation source to support various millimeter-wave devices.The extended interaction klystron amplifier has the characteristics of high gain,high power,and can be miniaturized,so it is always the focus of the research of vacuum devices.In this paper,a new high-frequency structure formed by the combination of subwavelength hole array and traditional ladder-type structure is adopted to design EIA.The details are shown as follows:An extended interaction klystron amplifier based on the traditional ladder-type structure combined with trapezoidal subwavelength hole arrays is proposed.To begin with,the field distribution characteristics in the single gap of the resonant cavity adopting traditional ladder-type structure with subwavelength hole arrays are analyzed,and it is determined that the resonator works best at TM₃₁-2?mode to meet the needs of our design of EIA.Then the transverse structural parameters were adjusted,including the width and height of the resonator cavity,the width and height of the coupling cavity,the shape and size of the subwavelength hole,etc.,to explore the influence of these parameters on the electric field distribution,dispersion characteristics and coupling characteristics.It is concluded that the resonant cavity height h₀ has the greatest influence on the resonant frequency,and the resonant frequency has little change when the width of the coupling cavity hr increases.As for the characteristic impedance,the change of the resonator height h₀ basically has no effect on R/Q,and increasing the width of the coupling cavity hr or decreasing the width of the resonator cavity w will lead to a rapid increase in R/Q.After making the resonator with subwavelength hole array work at the optimum status,it was used as the intermediate cavity of EIA in this paper,and the fault tolerance ability of the structure to the asymmetry produced by fabrication was briefly analyzed.According to the novel high frequency structure's performance,the cross-section shape of the sub-wavelength hole is changed into a rectangle.The input and output cavities working in TM₁₁-2?mode and the input and output cavities working in TM₃₁-2?mode are designed respectively.The input-output cavity working in TM₁₁-2? mode was selected to design EIA,and the cavity wall conductivity of the resonant cavity was set to 5.8*10⁷ S/m.EIA employs a six-cavity structure,and each intermediate cavity is tuned to obtain a wider bandwidth.The operating parameters were adjusted to make EIA work in the best position.Finally,the electronic injection voltage was adjusted to 14.8 k V,the working current was 74 m A,the input signal power was 20 m W,and the frequency was 230.7 GHz.We obtained the EIA working in millimeter wave band,the gain was 28.53 dB,the output power was 14.26W,and the bandwidth of-3dB was over 1.3 GHz.The bandwidth with a gain of more than20 dB is defined as the working bandwidth,and the working bandwidth of the EIA exceeds 2.7 GHz.Since the resonant frequencies of the two resonators mentioned above EIA are exactly the same,when the input frequency is close to the resonant frequencies of the two cavities,the modulation of the electron injection will be too deep and the phenomenon of over-bunching will appear,making EIA unable to be completely stable.In addition,electron injection into the output cavity of the EIA has a weak beam-wave interaction.Therefore,at first,the input and output cavity working in TM₃₁-2?mode was re-selected to design EIA.The electrical conductivity was set as 2.5*10⁷ S/m,and the value of Q was lowered to reduce the oscillation in the cavity.The operation parameters of EIA are adjusted to make it work in the best condition.When the electronic injection voltage is 14.9 k V,the current is 0.78 A,and the input power is 20 m W,the optimized millimeter-wave EIA with excellent performance at 230.7 GHz,gain of 44.69 dB,output power of589 W,efficiency of 5.07%,-3dB bandwidth of more than 1.1 GHz is obtained.Finally,by adjusting the structural parameters of the input and output cavity,adjusting the length of the drift tube and reducing the magnetic field to 0.38 T,the current was reduced to 0.29A,the input frequency was 231 GHz,the power was 20 m W,and finally the EIA with gain of 35.05 dB,output power was 64 W,and the bandwidth of-3dB was more than 1.1GHz.