High-Power Backward-Wave Oscillator Using Folded Waveguide With Distributed Power Extraction Operating at an Exceptional Point

The concept of exceptional point of degeneracy (EPD) is used to conceive an exceptional synchronization regime that is able to enhance the level of output power and power conversion efficiency for backward-wave oscillators (BWOs) operating at millimeter-wave and terahertz frequencies. Standard BWOs operating at such high frequency ranges typically generate output power not exceeding tens of watts with very poor power conversion efficiency in the order of 1%. The novel concept of exceptional synchronization for the BWO based on a folded waveguide is implemented by engineering distributed gain and power extraction along the slow-wave waveguide. The distributed power extraction along the folded waveguide is useful to satisfy the necessary conditions to have an EPD at the synchronization point. Particle-in-cell (PIC) simulation results show that BWO operating at an EPD regime is capable of generating output power exceeding 3 kW with conversion efficiency of exceeding 20% at frequency of 88.5 GHz.