Demonstration of a 220-GHz Wideband High Power Low Reflection Folded Waveguide Traveling-Wave Tube

In this article, we propose a low reflection folded waveguide (LRFWG) as the slow wave structure (SWS) for the development of a terahertz (THz) traveling-wave tube (TWT). Our simulation results show that the LRFWG SWS has lower reflection and larger coupling impedance compared to the conventional folded waveguide (FWG) SWS over a wide frequency range. Using this modified SWS, we have designed, simulated, and manufactured a wide-band high-power TWT operating in the G-band. The cold test results demonstrate that the reflection parameters at the input and output ports of the TWT are less than -13.8 dB from 200 to 240 GHz, confirming the effectiveness of our proposed structure. In addition, the hot test results show that the maximum output power of the 220 GHz LRFWG TWT amplifier reaches 31.2 W at 220 GHz, with a 3 dB bandwidth exceeding 23 GHz. The power-bandwidth product of the device is greater than 717.6 W
$\cdot $
GHz, providing a demonstration of a wideband high power THz source.