基于TM03模式的V波段同轴渡越时间振荡器设计

Design of V-band coaxial transit time oscillator with TM03 mode

随着高功率微波源频率的提升,腔体尺寸会随着电磁波波长的缩短而减小,从而导致器件功率容量不足,增大了射频击穿、脉冲缩短的风险。为了提升高频器件的功率容量,提出了一种基于TM03模式的低表面场强V波段同轴渡越时间振荡器,通过引入TM03模式的方式在极高频下拓宽腔体的横向尺寸,从而降低表面场强,提升功率容量。为了激励TM03模式并使之成为器件主要工作模式,计算了束波互作用结构的色散曲线及耦合阻抗,通过腔体设计使TM03模式的相速度与电子速度同步并发生换能,从而获得较低的群速度以及较高的耦合阻抗,最终成功在慢波结构中建立起了TM03模式电磁场。随后的粒子模拟仿真表明,在二极管电压400 kV、电流5 kA的条件下,输出微波功率达440 MW,频率为62.25 GHz,转换效率为22%,最大表面场强为1.6 MV/cm。

Increasing frequency is always an important development direction of high power microwave(HPM).However,as the frequency increases,the volume of an HPM device decreases rapidly and so does the power handling capacity(PHC).For obtaining reasonable PHC,the design of a V-band coaxial transit time oscillator(TTO)based on TM03 mode is carried out to achieve low surface field in this paper.The slow wave structure(SWS)having a large radial width with TM03 mode in such a device designed will lead to low risk of both electric field breakdown and pulse shortening.Firstly,the synchronous effect of velocity between microwave and electron beam is achieved by calculation of dispersion curve and coupling impedance.Then,small group velocity and high coupling impedance are designed to make TM03 a dominant mode in the coaxial V-band TTO.Finally,under the condition of 440 kV and 5 kA,an HPM is generated to reach an output power of 440 MW with a low surface electric field of 1.6 MV/cm,a microwave frequency of 62.25 GHz,and a beam-to-wave efficiency of 22%from numerical simulation.