基于大过模比同轴慢波结构的60GHz高阶模高功率相对论返波振荡器研究

The 60 GHz high-power millimeter wave has important application in directed energy, electronic warfare, radar and other defense fields. The development of 60 GHz millimeter-wave source with high power and high efficiency has become a hot-spot in the field of high power microwave technology. In the previous research, the hollow slow wave structure or the coaxial slow wave structure with the low-order operation modes has been used, which have a very small transverse size of beam-wave interaction cavity and a very narrow e-beam transmission channel. In such devices, the power capacity is difficult to improve, and the effective transmission of the actual intense relativistic electron beam cannot be achieved. Thus, almost no feasible experimental scheme and experimental results were reported. This project proposes a novel 60GHz relativistic backward wave oscillator based on the TM02 mode. Due to high-order operation modes, it has large size of beam-wave interaction cavity and a very wide e-beam transmission channel, with the merits of high power capacity and experimental feasibility. Through the research on key theoretical and technical problems of suppressing mode competition and improving power capacity, a V-band high power and high efficiency millimeter wave source will be designed and verified. In experiments, 60 GHz high-power millimeter wave is expected to be obtained with power more than 200 MW, efficiency more than 20 %, and pulse width more than 20 ns.

60GHz高功率毫米波在定向能、电子对抗、雷达等国防领域有重要应用价值，研制60GHz高功率毫米波源是目前高功率微波技术领域的研究热点。在以往相关研究中，主要采用空心慢波结构或工作在低阶模的同轴慢波结构技术方案，受模式竞争问题限制，器件的横向尺寸和电子束传输通道较小，造成功率容量难以提高、无法保证实际强流相对论电子束的有效传输，因此仅限于粒子模拟研究，未见可行的实验方案和实验结果报道。本项目提出一种新型60GHz同轴TM02模相对论返波振荡器。该器件工作在高阶模、高频结构尺寸大、电子束传输通道宽，因而具有功率容量高、实验可实现性强等优点。通过对抑制模式竞争、提高功率容量等关键理论和技术问题的研究和粒子模拟优化，设计出具有实验可行性的V波段高功率毫米波源并开展实验验证，获得功率大于200MW、效率大于20%、脉宽大于20ns的60GHz毫米波输出。

本课题研究目标和研究内容均按照计划开展而完成。本项目首先从理论上全面系统分析大过模比同轴慢波结构混合模式工作的可行性，数值求解了同轴慢波结构的色散关系和增长率，以及同轴不连续结构的反射和谐振特性，提出慢波结构应满足的理论条件，在此基础上研究了同轴慢波结构中非旋转对称模式优先激励的机制，提出了一种抑制大过模同轴慢波结构中非旋转对称模式的新方法，为设计具有高功率容量、高效率的V波段Cerenkov型振荡器提供理论依据。根据理论分析结果，设计出具有高功率容量、宽电子束传输通道、满足实际实验要求的60 GHz同轴高功率微波振荡器，粒子模拟在电压355 kV、电流3 kA 注入下，获得了混合模式工作、中心频率62.6 GHz、平均功率335 MW、效率32% 的高功率毫米波输出。最后根据理论和仿真设计结果，完成器件性能的实验验证，在二极管电压为350 kV、导引磁场为2.0 T 条件下，高能电子束可以稳定有效的传输，器件可产生功率约239 MW、频率为63.2 GHz、脉宽18 ns 的微波输出。该器件具有结构紧凑、工作状态稳定的特点，工作机制与三维仿真设计结果基本一致，其功率和脉宽均为近年来公开报道的最高水平。