优化设计了一种220 GHz的折叠波导慢波结构的尺寸，对其冷测特性如色散、耦合阻抗和衰减进行了分析。理论分析和软件仿真结果表明设计的折叠波导慢波结构在中心频率处具有较平缓的色散关系，较高的耦合阻抗和较低的电路衰减。互作用模拟表明，在电子注电压为20 kV，电流为10 mA时，27 mm(50个周期)的折叠波导慢波结构在220 GHz具有14.5 dB的增益，3 dB带宽为16.3 GHz(211.9～228.2 GHz)。

A 220 GHz folded waveguide slow-wave structure is designed and its dispersion relation, interaction impedance and circuit attenuation are analyzed. The simulation results show good agreement with the theoretical formula analysis. The folded waveguide slow-wave structure has broad cold bandwidth about 119 GHz, flat dispersion relation, fairly high interaction impedance about 3 Ω and low circuit attenuation for a 220 GHz central frequency. The large signal performance of 27 mm (50 periods) folded waveguide circuit is predicted. Simulations show that the nonlinear gain is 14.5 dB at 220 GHz where beam voltage and current are 20 kV and 10 mA, respectively. A saturated 3 dB bandwidth is 16.3 GHz (211.9 GHz to 228.2 GHz).