建立了自洽的考虑波导璧损耗的折叠波导等效电路模型,用来计算该慢波结构周期TE10模式中各次空间谐波的相速度,耦合阻抗和线衰减系数.分析结果将会用到220 GHz折叠波导返波管一维束波互作用模型的计算中.当微波频率上升到太赫兹波段时,粗糙波导表面电流导致的壁损将不能再忽略不计.进一步研究表明,起振电流和输出功率水平将和损耗特性的计算密切相关.从原有模型发展而来的有损电路模型可以给出更准确损耗估计.建立了折叠波导慢波线三维谐振腔模型来验证本文的等效电路理论,有较好的吻合.采用了该理论导出参数的一维束波互作用模型和三维数值PIC方法同样有很好的一致性.

The equivalent circuit model (ECM)of the folded waveguide (FW) in consistent consideration of the ohm loss on the waveguide wall was established for calculating the cold-circuit phase velocities, interaction impedance and attenuating coefficient of space harmonics of periodic TE10 mode in this slow wave structure (SWS). These results were obtained for one-dimensional (1-D) parametric model calculation of the particle-microwave interaction in the 220 GHz backward wave oscillator (BWO). When the frequency of microwave is up to terahertz regime, the ohm loss caused by surface current on rough waveguide wall is not negligible any more. Further study shows that the starting oscillation current and output power are intimately dependent upon the loss property calculation. The ECM about lossy periodic circuits was then developed from the previous loss-free model to give a more accurate analysis. Three-dimensional (3-D) Eigen mode analysis for the FW SWS was taken to verify the improved model, which shows good agreement. Additionally, based on the improved ECM, 1-D beam wave interaction calculation was conducted which is in good consistency with 3-D Particle-in-cell (PIC) method.