A W-Band TE12-Mode Input Converter With Nonuniform Bragg Cavities

A method to launch a circular TE
₁₂
mode as the input converter of a W-band high-order mode gyrotron travelling wave tube was proposed and verified by the simulation and cold test. The TE
₁₂
mode is stimulated by a broadband Y-type power divider. Instead of the cutoff waveguide, a nonperiodic Bragg reflector was adopted to overcome the issues of smaller beam tunnel dimensions and higher electron interception. Simulation design reveals that two different kinds of Bragg reflectors can achieve the performance we need. Identical converters with and without the corrugated reflectors for the back-to-back millimeter wave measurements were manufactured using the computerized numerical control technique. Vector network analyzer measurements of the converter transmission, reflection, and isolation are all in good agreement with our simulated results.