Power Enhancement in W-Band Pulsed Folded Waveguide TWT

To obtain higher power in W-band traveling-wave tubes (TWTs), a modified folded waveguide (FWG) with non-concentric bends is introduced and demonstrated, which has higher coupling impedance compared with the normal FWG structure and is utilized to eliminate the band-edge instability of TWT. Phase velocity tapering (PVT) is also used to improve the interaction efficiency between the beam and the circuit. Furthermore, a higher beam current is used and the corresponding magnetic focusing system is designed to confine the beam. A prototype tube was then fabricated and tested at a beam current of 220 mA and beam voltage of 21.9 kV. The testing data show that this W-band TWT is capable of delivering an output power of over 450 W with a 4.5-GHz bandwidth at a duty cycle of 10%, with a maximum power of 647 W and electronic efficiency of 13.4%. That is the highest output power and electronic efficiency test results of W-band TWTs reported so far.