Gehrmann, ElkeElkeGehrmannBirtel, PhilipPhilipBirtelDürr, WolfgangWolfgangDürrJacob, Arne F.Arne F.Jacob2021-01-132021-01-132014-06IEEE Transactions on Electron Devices 6 (61): 6719490 (2014)http://hdl.handle.net/11420/8393Increasing the efficiency of traveling wave tubes (TWTs) is a basic development strategy. In this paper, second harmonic suppression is introduced as a possible mean. For this purpose, a filter consisting of periodic pitch discontinuities is implemented in the helix transmission line (TL) of a tube. A method is developed to obtain the reflection coefficients of adjustable pitch discontinuities. A filter design for a low frequency TWT is tested in a helical TL without electron beam and implemented in the tube. Both simulation and measurement confirm a stopband at the second harmonic and thus a significant reduction of this harmonic at the output. An additional filter is designed and tested at S-band. It is shown to improve both the output power and the linearity of the tube.en0018-93832014618591864Efficiencyfilterharmonicreflectionstraveling wave tube (TWT)Allgemeines, WissenschaftJournal Article10.1109/TED.2013.2296150Other