利用粒子模拟(PIC)三维软件，在Ka波段，采用扩展互作用谐振腔技术和谐振腔加载技术来实现高增益和宽频带，对扩展互作用速调管进行了设计和粒子模拟仿真，同时采用二维电子光学软件EGUN对电子枪和聚焦系统进行了设计和优化，聚焦系统使用的是钐钴永磁聚焦。在工作电压9 kV，束流0.15 A的条件下，输入功率为200 mW时，中心频率35.5 GHz， 3 dB带宽为410 MHz，最小增益为32.5 dB，得到效率为26%，其平均功率为355 W。

The preliminary design of a Ka-band extended interaction klystron is presented with three-dimensional particle-in-cell(PIC) code. The extended interaction technology is widely adopted in resonant cavities used for high power, high gain, and bandwith applications. The electron gun and the focusing system are separately designed and optimized, where a permanent magnetic focusing scheme is introduced. The klystron is driven by a 0.15 A, 9 kV round-electron beam. An output average power of 355 W is achieved with an input power of 200 mW, corresponding to the gain of 32.5 dB , the efficiency of 26%, and the bandwith of 410 MHz at the centeral frequency.