A Novel Slow-Wave Structure—Folded Rectangular Groove Waveguide for Millimeter-Wave TWT

A novel slow-wave structure (SWS) called the folded rectangular groove guide, its electromagnetic characteristics, and the beam-wave interaction are presented. This structure, evolved from a conventional rectangular groove guide by bending the groove along its longitudinal direction, can operate with the sheet electron beam or the circular electron beam. From our calculations, this SWS possesses larger interaction impedance and lower ohmic loss than those of a folded rectangular waveguide with the same size. This circuit can produce output power of over 260 W with a sheet electron beam in the 3-dB bandwidth range of 88.5.5–98.5 GHz when the cathode voltage and beam current are set to 19.45 kV and 150 mA, respectively, whereas the folded rectangular waveguide can produce output power over 245 W in the 3-dB bandwidth range of 84–89 GHz.