Filter helix implementation into an S-band TWT design

The performance of an S-band traveling wave tube (TWT) is enhanced by introducing a filter consisting of periodic transmission line discontinuities into its delay line. The filter is designed to suppress the second harmonic which is particularly strong in this tube especially at low frequencies. The main goal, i.e. to improve the electron velocity spectrum at the lower operating band and, thus, to extend the bandwidth of the tube, is demonstrated.