Linear analysis of folded waveguide tube in terahertz band
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摘要: 给出了太赫兹波段折叠波导行波管中考虑管壁欧姆损耗的带电子束扰动的色散方程。求解该方程可以得到器件中小信号增益的值。通过编制Matlab程序,分析计算了不同工作点、不同折叠波导结构参数和不同工作频段时小信号增益的变化特性。计算结果表明:适当选取工作点和结构参数,可以获得最佳增益值;考虑损耗后,除了前向增长的辐射场外,还会出现反向传输的静态波;随着工作频段向高频方向延伸,前向波的增益显著降低,而反向波强度则增大。因此,工作频率提高时,为了达到一定大小的增益,需要的折叠波导的周期数也相应增加。Abstract: Perturbed dispersion relation considering the ohmic losses of the waveguide wall in folded waveguide tube is derived and solved by using Matlab. Small signal gain increases with the increasing of ratio of the center frequency to the cutoff frequency, but the increase will be slower with further increasing of the ratio and the band width becomes narrower, as calculation results show. With the beam current density fixed, there exist optimal values of the width of the beam tunnel and the width of the cross section for the maximum gain. A quiescent waveguide mode propagating backward appears in the waveguide while taking the ohmic losses into consideration. With the increasing of the operating frequency, the gain decreases obviously while the intensity of the quiescent waveguide mode is enhanced. Therefore, for a folded waveguide tube operating at higher frequency in terahertz band, the period number of the folded waveguide increases correspondingly.
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Key words:
- folded waveguide tube /
- terahertz /
- small signal gain /
- ohmic losses
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