A High Efficiency 100-W E-band Continuous Wave Traveling Wave Tube

A continuous wave (CW) E-band traveling wave tube (TWT) is developed to meet the demand of broadband, high power and high efficiency amplifiers for future wireless communications. Several methods are combined to improve the TWT performance, in particular the efficiency, including: increase of the interaction impedance by setting operation point near the cutoff frequency, use of the folded waveguide (FWG) slow wave structure (SWS) with modified circular bends (MCBs) and the phase velocity jumping (PVJ) technique. A novel dual-mode asymmetry multistage depressed collector is used to significantly improve the recovery efficiency without the return of electrons. The first prototype tube has been assembled and tested. A total efficiency of 43% with an electronic efficiency of 9.8%, output power of 120 W and gain of 41 dB is achieved in 81-86GHz where the beam voltage is 15.8kV and the beam current is 77mA. The tube shows very flat output characteristics in saturation state and provides high linear power and efficiency. The -1dB compression point output is over 50W with the linear (output back off 4dB) total efficiency up to 26.4%.