A time-division low-magnetic-field Ku / Ka dual-frequency relativistic transit-time oscillator based on axial tuning

With the widespread application of high-power microwave (HPM) technology in directed energy and plasma heating, the demand for multi-frequency time-division output has grown significantly. This paper proposes an axially tuned time-division low-magnetic-field Ku/Ka dual-frequency relativistic transit-time oscillator (RTTO), adopting a coaxial cascaded structure. Benefiting from the characteristics of the RTTO, the dual-frequency resonant cavities are naturally isolated from each other. On this basis, band switching is realized through axial displacement of a single tuning conductor, featuring fast and accurate tuning performance. An internal and external dual-coaxial independent output structure is adopted, effectively avoiding coupling interference between dual-frequency and facilitating subsequent engineering design. Particle-in-cell simulation results show that under 0.5 T low magnetic field, the device achieves stable cross-band time-division output in Ku/Ka-band with both 700 MW output power and 29% efficiency; 200 ns long-pulse simulations verify stable operation without mode competition; actual pulse power system voltage simulations confirm operational reliability under real conditions. This low-magnetic-field device enables permanent magnet packaging, combining single electron beam operation, rapid online tuning, and compact design, with promising applications in lightweight dual-frequency HPM systems.