Development of Micromachined G-band Energy-Recirculating Folded Waveguide Traveling-Wave Tube Oscillator

We present development results of an energy-recirculating folded waveguide traveling-wave tube oscillator internally driven by a backward-wave oscillator (BWO). The BWO, as a driving source, converts the beam energy achieved from electrostatic energy to electromagnetic energy. The generated radio frequency signal in the BWO is amplified in the traveling-wave tube using the spent electron beam as an energy-recirculating method. We exhibit a detailed design process and analysis of the individual circuits, as well as those of the combined circuit, which are simulated using the CST Particle Studio and MAGIC code. A maximum average output power of 43.55 W at a frequency of 272.2 GHz is obtained in simulation under a consideration of ohmic loss with conductivity 5.51 × 10⁷ S/m. The experimental results will be presented and compared to the simulation result. A nanocomputer numerical control (nano-CNC) machining technique was used for manufacturing FWGs. Manufactured FWGs operating in the G- (110–300 GHz) and Y-bands (325–500 GHz) demonstrated the highest reported root mean square surface roughness less than 21 nm in the Y-band. Detailed fabrication process and results of the FWGs using nano-CNC machining will be presented in detail.