Mode conversion in helix loaded waveguide

Forward coupling of a fast TE-like mode is an interesting and desirable option in the gyro-TWT amplifier. We consider in this paper a mode conversion at the abrupt junction of two infinitely long sheath-helix-loaded waveguides. A helix mode traveling from the left to the right side excites fast TE-like modes are numerically calculated by taking dominant terms in the into TE-like modes are numerically calculated by taking dominant terms in the eigenmode-expansion method. The bandwidth (3 dB) for TE-mode-like coupling in the second (right-hand-side) waveguide is found to be over 40$.