Optimization of helix pitch profile for broadband Mini-TWTs

Broadband helix traveling-wave tubes (TWTs) with a pitch profile incorporating a section of reduced phase velocity followed by a positive taper show significant improvement in output power. A simple technique is described here to optimize such slow-wave structures taking an existing uniform pitch mini-TWT as a baseline tube. A comparison has been made among the actual performances of the TWTs with three different pitch profiles such as, uniform, positive taper and negative step positive taper. It has been observed that the improvement in output power is highest for the last TWT over 6-18 GHz operating band.