提出脊加载同轴径向线慢波结构，并用高频结构仿真器(HFSS)电磁仿真软件对其色散特性和耦合阻抗进行研究，分析了不同结构参数变化对其高频特性的影响。结果表明：脊加载同轴径向线慢波结构的色散曲线平坦，减小内径和周期长度可以明显降低慢波结构的相速，从而减小工作电压；加载脊的宽度对耦合阻抗的影响明显，随着加载脊宽度的增加，耦合阻抗得到提高，相速减小；加载脊的长度对结构的色散特性和耦合阻抗影响不明显；这种脊加载方式有利于增加慢波结构的耦合阻抗，提高行波管的增益和效率。脊加载同轴径向线慢波结构是一种全金属结构，工作频带宽，散热性能好，在毫米波波段的行波管中有较好的应用前景。

The ridge-loaded coaxial radial line slow wave structure is presented in this paper. The dispersion characteristic and coupling impedance of this slow wave structure are investigated by electromagnetic simulator High Frequency Structure Simulator(HFSS). It is analyzed that the change of structure parameter affects the high-frequency characteristics. The results show that the inner conductor radius and the period length have obvious effect on phase velocity. Along with the decrease of inner conductor radius and period length, the phase velocity and operating voltage can be favorably decreased. In addition, the width of the ridge makes the coupling impedance increase, when this structure is used as the slow wave structure, the gain and efficiency of the traveling wave tube can be improved. Meanwhile the length of ridge has no obvious effect on the high-frequency characteristics. Because the ridge-loaded coaxial radial line slow wave structure is a new all-metal structure with the advantage of broad bandwidth, high power capability and lower losses, it has a large potential of application in millimeter traveling-wave tubes.