The growing interest in wireless high data rate communications at millimeter waves both for terrestrial networks and satellite communications is stimulating novel solutions to overcome the strong atmosphere attenuation. In particular, the development of high throughput satellite communication systems for internet distribution is fundamental to complement the terrestrial networks and to cover regions not connected to terrestrial backbones, such as sea or remote areas. Ku-band and Ka-band satellite systems are presently available. Recently, the W-band (71 -76 GHz, 81-86 GHz) has been allocated for multigigabit transmissions, providing 5 GHz bandwidth both for uplink and downlink. However, it has been estimated that for enabling high throughput W-band satellite communication systems, transmission power higher than 50 W is needed. In this paper, a 71-76 GHz double corrugated waveguide (DCW) traveling wave tube (TWT) is designed as amplifier for high-data rate satellite downlink, with about 70 W output power. The dispersion characteristic of the designed DCW is experimentally validated by cold test. The proposed TWT is also a test vehicle, scaled in frequency, for a future novel 220 GHz DCW TWT for terrestrial wireless networks.