A millimeter wave relativistic backward wave oscillator operating in TM₀₃ mode with low guiding magnetic field

A V-band overmoded relativistic backward wave oscillator (RBWO) guided by low magnetic field and operating on a TM₀₃ mode is presented to increase both the power handling capacity and the wave-beam interaction conversion efficiency. Trapezoidal slow wave structures (SWSs) with shallow corrugations and long periods are adopted to make the group velocity of TM₀₃ mode at the intersection point close to zero. The coupling impedance and diffraction Q-factor of the RBWO increase, while the starting current decreases owing to the reduction of the group velocity of TM₀₃ mode. In addition, the TM₀₃ mode dominates over the other modes in the startup of the oscillation. Via numerical simulation, the generation of the microwave pulse with an output power of 425 MW and a conversion efficiency of 32% are achieved at 60.5 GHz with an external magnetic field of 1.25 T. This RBWO can provide greater power handling capacity when operating on the TM₀₃ mode than on the TM₀₁ mode