针对器件工程应用中的高功率高增益需求，设计了工作在X波段的高功率高增益多注相对论速调管放大器，建立了带输入、输出波导结构的三维整管模型。设计双边对称耦合孔输入腔结构，降低了输入波导对输入腔间隙电场均匀性的影响以抑制非均匀干扰模式；设计采用多腔多间隙群聚结构，降低了输入微波功率的需求，提高了器件放大增益；并且分析设计了多间隙扩展互作用微波提取结构，提高了器件的功率转换效率以及降低输出结构表面电场强度。通过优化设计，粒子模拟仿真实现X波段多注相对论速调管放大器输出微波功率达到3.2 GW，器件放大增益约为60 dB，功率转换效率约为40%。器件验证实验在电子束电压550 kV，电流5.1 kA的情况下，输出功率为0.99 GW，放大增益约为53 dB，转换效率约为35%。

To meet the high power and high gain requirements in engineering applications, we''ve designed a three-dimensional whole tube model for an X-band high-power high-gain multi-beam relativistic klystron amplifier. This paper presents the high frequency characteristic analysis and the tube with the integrated model. The input cavity structure with bilateral symmetric coupling hole is designed to reduce the influence of the input waveguide on the field uniformity of the input cavity gap. A multi-cavity and multi-gap modulation structure is adopted to reduce the requirement of input microwave power and improve the amplification gain. Moreover, the multi-gap spreading interaction extraction structure is analyzed and designed to improve the power conversion efficiency and reduce the surface electric field intensity, so as to control the risk of RF breakdown of the device. A three-dimensional full electromagnetic particle in cell code is used to simulate the absorption of injected microwave, and the fundamental harmonic modulated current when electron beams propagate through the input cavity and middle cavity gaps have also been simulated. A 3.2 GW averaged microwave power over the oscillator period is generated by simulation with 900 kV electron beam voltage, 9 kA current and 1 T leading magnetic induction intensity, the efficiency is 40% and the amplification gain is 60 dB. In the experiment, a 0.99 GW average microwave power was generated with 550 kV electron beam voltage, 5.1 kA current, 35% efficiency and 53 dB amplification gain.