中文摘要：

本文设计了220 GHz三注折叠波导慢波电路,并对其放大特性进行了分析。利用等效电路法对慢波电路结构色散特性与轴向耦合阻抗进行了计算,并通过三维高频仿真软件HFSS进行了模拟验证。利用三维电磁仿真软件CST-PS的PIC求解器对该慢波结构的三维大信号的注波互作用进行了粒子仿真,结果表明：在工作中心频率为220 GHz时,三注折叠波导慢波电路输出功率达到49.7 W,增益达到了37.05 dB,3 dB带宽为13 GHz（212～225 GHz）。最后分析了边缘电子注的注电压和注电流的减小对该结构放大性的影响。

英文摘要：

The newly-designed 220 GHz three-beam folded waveguide slow-wave circuit was empirically approximated with an equivalent circuit,theoretically analyzedand numerically simulated in finite element method with HFSS software. The highfrequency dispersion characteristic and coupling impedance were investigated. The calculated and simulated results were found to be in good agreement. Besides,the interaction of the electron beam and electromagnetic field in a 3-D large signal was simulated with software PIC,CST-PS. The simulated results show that operated at 220 GHz,the newly-designed three-beam folded waveguide slow-wave circuit had a highest output power of 49. 7 W,a gain of 37. 05 d B,and 3 d B bandwidth of 13 GHz（ 212 ～ 225 GHz）. We found that the new structure can effectively suppress the internal reflection because of its shorter beam-wave interaction length,and its reduced width is favorable for design of the magnetic focus system.