Design and test of wideband 0.22 THz folded-waveguide travelling wave tube

In order to develop a wideband 0.22 THz folded-waveguide travelling wave tube, a slow wave structure and RF window are carefully designed. By theoretic analysis and simulation, the tube will work at the point where the dispersion curve is flat and instantaneous bandwidth is more than 16 GHz. In more than 30 GHz, S11 of the RF window is better than -25 dB. The experimental result of the first prototype tube shows that the instantaneous bandwidth is only about 8 GHz. After optimization, the instantaneous bandwidth of the second prototype tube becomes more than 12 GHz with an output peak power more than 400 mW.