This work describes the design of a folded waveguide traveling wave tube (TWT) operating in G- band around 145 GHz. In order to achieve high output power and good linearity a new parallel approach, using a single electron beam, was used. The designed TWT showed a maximum saturation gain of 39 dB with a bandwidth of 8.3 GHz. The parallel configuration has better RF performances respect to a standard FWG-TWT without increasing the complexity of fabrication.