Summary form only given. Gyro-BWOs are efficient sources with wide frequency tuneability and high power capability from the microwave to terahertz frequency range. The helically corrugated waveguide couples two modes in the circular waveguide to generate a new operating eigen-mode which has large group velocity in low axial wavenumber range. Gyro-BWOs based on helically corrugated waveguides can achieve even wider frequency tuning range and higher efficiency. A W-band gyro-BWO currently being built at the University of Strathclyde achieves a 3 dB frequency bandwidth of 84-104 GHz, output power of 10 kW with an electronic efficiency of 17% in the simulations. The recent progress on the experimental study of the W-band gyro-BWO is presented in this paper.
- backward wave oscillators