Abstract: The development of modern vacuum electronics technology has placed higher demands on the operating frequency band, bandwidth, and electronic efficiency of traveling wave tubes (TWTs). To meet the new challenges in next-generation satellite communications, this paper studies a W-band TWT based on a modified rectangular-ring vertex double-bar (RRVDB) slow wave structure (SWS). Based on a detailed analysis of the high-frequency characteristics of the SWS, the optimized parameters of the RRVDB SWS with flat dispersion and high interaction impedance were obtained, and greater interaction impedance can be achieved by utilizing comparatively thinner connecting bars. Using a side-coplanar input-output coupler, good transmission with S₁₁ < −22.1 dB was achieved in the 70−110 GHz frequency range. PIC simulation results show that under the conditions of a 10250 V electron beam voltage and a 0.096 A operating current, the RRVDB TWT can provide a maximum output power of 77.15 W at 99 GHz, corresponding to a differential gain of 1.47 dB/mm and an electronic efficiency of 7.84%, with a 3 dB bandwidth reaching 14 GHz (87~101 GHz).