Technology, Assembly, and Test of a W-Band Traveling Wave Tube for New 5G High-Capacity Networks

Abstract

The folded waveguide (FWG) traveling wave tube (TWT) developed in the frame of the Horizon 2020 TWEETHER project for enabling a novel W-band (92-95 GHz) high capacity wireless network for 5G, is presented. The FWG TWT was designed by particle-in-cell simulations. The technology and the results in terms of measured RF losses and beam transmission from the realized beam tester are presented. Amplification on the first TWT breadboard has been observed but with a poor multi-reflection pattern resulting from spurious burrs inside the folded waveguide. It indicates however that the FWG technology offers great manufacturing simplification compared to conventional helix TWTs, thus enabling a low-cost device with large series production suitable for the wide market of wireless communications.

Millimeter wave traveling wave tubes for the 21st Century

“…Currently, the maximum operating frequency for space TWTs is about 70 GHz. However, it is already envisaged the use of E-band (71)(72)(73)(74)(75)(76)(77)(78)(79)(80)(81)(82)(83)(84)(85)(86) for very high data rate satellite communications [12].…”

“…However, when the size of the features, as in millimeter wave SWS, approaches the 100 micron level and the surface roughness needs to be in the range of tens of nanometers, the process become very challenging and high end equipment is needed. The quality of fabrication is a function of the accuracy and resolution of the positioning and the availability of suitable toolings and high spindle speed (higher than 20,000 rpm) [79][80][81][82][83]. High-end CNC mills available in the market provide resolution of about 100 nm.…”

“…Figure 13 shows two SWSs produced by a commercial high speed CNC milling (Primacon) with better than 1 micron accuracy. Figure 13(a) shows a 92-95 GHz folded waveguide, specifically one of the two identical halves that once assembled formed the closed waveguide [82]. Figure 13(b) shows a 140 GHz double corrugated waveguide [83].…”

“…The alignment of the two halves has to be highly accurate, otherwise the electromagnetic properties could be degraded. As an example (Figure 21), about 10 micron misalignment between the two halves (a) in a 92-95 GHz FWG generates a stop band at about 94 GHz (b), making the FWG not usable [82]. The improvement of the alignment accuracy permitted to remove the rejection band.…”

“…(a) High precision CNC milling (a) W-band Folded Waveguide[82] and (b) D-band double corrugated waveguide[83].…”