周期加载波导中匀速带电粒子的衍射辐射是产生较高频段可调谐太赫兹电磁辐射(频率高于1 THz)的有效方法.对圆柱形周期加载波导中偏心电子注产生的衍射辐射现象,进行了严格的理论分析和粒子模拟验证.研究表明,偏心电子注在波导中除了激励起角向对称模(TM_0波)以外,还将激励起角向模式为1(HE_1波)和2(HE_2波)的角向非对称模.并且电子注偏离轴线距离越大,激励的角向非对称模场强越强.每个模式的功率随电子注的激励位置呈变态贝塞尔函数平方关系变化,与电子注电流平方成正比.理论分析与计算机模拟的结果符合较好.研究结果将为发展该类可调谐太赫兹辐射源提供理论依据. Diffraction radiation of uniformly charged particles in periodically loaded waveguides is an effective method to generate higher frequency tunable terahertz electromagnetic radiation (frequency higher than 1 THz). The phenomenon of diffracting radiation generated by eccentric electron injection in a cylindrical periodic waveguide is studied Rigorous theoretical analysis and particle simulation.The results show that the excited electrons in the waveguide will excite the angular modes 1 (HE_1 wave) and 2 (HE_2 wave) in addition to the angular symmetry mode (TM_0 wave) The angular asymmetric mode field strength of the excitation is stronger.The variation of the power of each mode with respect to the square of the perturbation Bessel function with the excitation position of the electron injection is The square of electron injection current is proportional to the theoretical analysis and computer simulation results in good agreement.The results of the study will provide a theoretical basis for the development of such tunable terahertz radiation source.