The development of high capacity wireless networks, to satisfy the increasing demand of mobile high-speed internet, is stimulating the exploitation of the wide frequency bands in the millimeter and THz range. Above 100 GHz, the high atmosphere attenuation is the major obstacle for wireless links of adequate length, due to the low power available from solid state amplifiers. Traveling wave tubes are promising devices capable to generate multi-watt power at sub-THz frequency. In this paper, the design and performance of a Traveling Wave Tube in the 210-250 GHz band with about 1W output power will be described, to power a 40 Gigabits per second optical transmitter for 1 km point-to-point link. A novel approach for a simple and low-cost fabrication, based on the use of the double corrugated waveguide is proposed.

The first Point to MultiPoint wireless system at Dband has been designed and it is in advanced development. The European Commission H2020 ULTRAWAVE "Ultra capacity wireless layer beyond 100 GHz based on millimeter wave Traveling Wave Tubes" project aims to respond to the demand of high capacity at level of tens of Gigabit per second, in urban areas, where fiber backhaul is not economical viable and high density small cell architectures are deployed. A transmission hub powered by novel D-band TWT will feed a number of terminals arbitrary allocated in the corresponding area sector. This paper illustrates the main characteristics, advantages and networking aspects and provide a summary of the latest results of the ULTRAWAVE project.

Ubiquitous wireless distribution of multigigabit per second data rate for enabling new 5G and 6G paradigms can be only achieved by exploiting the wide frequency bands available in the sub-THz spectrum (90 -305 GHz). The high total attenuation at sub-THz, in particular due to rain and humidity, poses a substantial challenge to achieve long links, not yet resolved due to the lack of sources with adequate transmission power. Sub-THz traveling wave tubes are emerging as key components to ensure high signal to noise ratio over a large coverage area or for long distance. This paper will describe the design and fabrication of a novel TWT for enabling point to multipoint wireless distribution at D-band (141 -148.5 GHz). To be suitable for the wireless market, TWTs need to be low cost and of easy manufacture for large scale production. The proposed D-band TWT uses a double corrugated waveguide as slow wave structure and a new electron gun, both designed for easy assembly and low fabrication cost. The paper describes the design process, the development of the parts of the TWT and the first prototype assembly.

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