A 1-kW 32–34-GHz Folded Waveguide Traveling Wave Tube

Folded waveguide (FWG) traveling wave tubes (TWTs) are potential sources of wideband, high-power millimeter and terahertz wave radiation. However, low efficiency limits its application. In this paper, we discuss a design strategy to improve efficiency of the FWG TWT meanwhile how to avoid instability is also discussed. The critical factors for the slow-wave structure design and the sever design are analyzed. A phase velocity taper profile incorporating a positive period followed by a negative period is introduced into the design to improve the efficiency. A Ka-band FWG TWT was developed, which demonstrated the output power up to
${>}{\rm 1}~{\rm KW}$
in 2-GHz bandwidth and electronic efficiency up to
${>}{9.4\%}$
.