E-band (71 -76 GHz and 81 -86 GHz) is already used for point to point links with a few Gigabit/second data rate. Front-ends are powered by solid state amplifiers with about 2 -3 W output power. This output power values limit range and spectral efficiency and have to be compensated by high gain antennas. The availability of tens of Watt would allow higher spectral efficiency and long range, and the use of lower gain antennas for multibeam and area coverage. This paper reports the design and the initial fabrication of the first ever E-band Traveling Wave Tube (TWT) based on the double corrugated waveguide. A test short interaction structure TWT is in assembly phase as proof of concept with about 2 W output power. The final TWT is designed to provide about 70 W power and about 40 dB gain.
E-band (71 -76 GHz and 81 -86 GHz) is widely used for wireless point to point links with a few Gigabit/second data rate. E-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 allow 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 to solid state devices. Helix TWTs, typically built at microwaves, are very arduous to fabricate due to the extremely small diameter of an helix at E-band.This paper reports the design and fabrication of the first ever Eband TWT based on a full metal slow wave structure, the double corrugated waveguide. 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 E-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.
The design of a W-band traveling-wave tube (TWT) power amplifier based on a groove gap waveguide slow wave circuit is presented in this paper. The technology of gap waveguide is analyzed to aid the design of electromagnetic band gap based slow wave structures in the upper millimeter wave range of the spectrum while alleviating some of the typical fabrication challenges at these frequencies. The results of Particle-In-Cell (PIC) simulations numerically demonstrate a 10-GHz instantaneous 3-dB bandwidth in the range 89-99 GHz with a minimum power gain of 25 dB. A prototype of the complete slow wave structure is manufactured via computer numerical control (CNC) machining and measured to verify the cold simulation results. Machining tolerances and surface roughness are also investigated. The design approach via groove gap waveguide is flexible and can be extended to alternative rectangular waveguide based slow wave structures.
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