Design and Fabrication of E-Band Traveling Wave Tube for High Data Rate Wireless Links

Abstract

<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band (71–76 and 81–86 GHz) is widely used for wireless point to point (PtP) links with a few gigabit/second data rate. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band front ends are powered by solid-state amplifiers with about 1-W output power per module. This level of output power limits range and spectral efficiency in rain condition and has to be compensated by high gain antennas or backup low-frequency links with reduced capacity. The availability of tens of watts of transmission power would allows higher spectral efficiency and long range, and the use of lower gain antennas for multibeam and area coverage. Millimeter wave traveling wave tubes (TWTs) are gaining interest due to their higher power, more than one order of magnitude, in comparison with solid-state devices. Helix TWTs, typically built at microwaves, are very arduous to fabricate due to the extremely small diameter of a helix at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band. This article reports the design and fabrication of the first ever <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band TWT based on a full metal slow wave structure (SWS), the double corrugated waveguide (DCW). The TWT is designed to provide about 70-W power and more than 35-dB gain in the 71–76-GHz band. A test TWT using a single section interaction structure is in the final assembly phase as proof of concept with about 2-W output power. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{E}$</tex-math> </inline-formula> -band TWT performance will open new perspectives in the availability of long range wireless links with multi-Gb/s data rate needed for enabling 5G and 6G new networks.