Design and Performance Evaluation of a Ka-Band Radial Staggered Double Vane Backward Wave Oscillator

This article introduces a radial staggered double vane (RSDV) backward wave oscillator (BWO) using a radial sheet electron beam (RSEB) to overcome the limitations of traditional Ka-band BWOs. Traditional BWOs face limitations due to a decrease in interaction space as frequency increases, leading to lower efficiency and considerable challenges in mitigating thermal stresses. In addition, these devices typically require an external magnetic field for beam focusing to counteract space charge effects, adding complexity to their fabrication. The RSDV slow wave structure (SWS) is designed, and its high-frequency characteristics are numerically analyzed. Particle-in-cell (PIC) simulations are conducted for the RSDV BWO using a converging RSEB without an external magnetic field, at a beam voltage of 20 kV and a current density of 22.43 A/cm². The device demonstrates enhanced efficiency over traditional Ka-band BWOs, achieving an average power of 117.61 kW and an efficiency of 10.69% at 31.02 GHz. Furthermore, the performance using a diverging RSEB setup is evaluated and compared with that of a converging RSEB. Coupled particle-thermal simulation confirms the device’s capability to effectively manage thermal stresses. The device, consisting of 18 periods, is fabricated and tested; cold-test results indicate an <inline-formula> <tex-math notation="LaTeX">${S} _{{11}}$ </tex-math></inline-formula> parameter around −10 dB at desired frequencies, aligning with simulated results. Moreover, a comparison between analytical, simulated, and measured dispersion curves based on <inline-formula> <tex-math notation="LaTeX">${S} _{{11}}$ </tex-math></inline-formula> phase is provided.