Linear theory of a folded waveguide traveling-wave tube (TWT)

A wideband folded waveguide traveling-wave tube (TWT) amplifier has the adv antages of simpler coupling structures and a robust structure over a conven tional helix TWT. The phase velocity of the waves in a folded waveguide is slowed down to the velocity of the electron beam. The slow-wave interaction with the electron beam in a folded waveguide is studied in a linear fashio n by using a field analysis. For a cold beam, the linear theory predicts a growth rate of 2 dB/cm with a bandwidth of 37 % at the center frequency of 14 GHz.