Design and Measurement of a Terahertz Double Staggered Grating Waveguide With an Arc-Shaped Beam Tunnel

Abstract

A millimeter-waveband double staggered grating waveguide (DSGW) with an arc-shaped beam tunnel was previously proposed for sheet beam traveling wave tubes. In this article, the design, fabrication, and cold test of a terahertz band DSGW with an arc-shaped beam tunnel are presented. Simulations demonstrated that the novel DSGW would have a higher coupling impedance and a better beam wave interaction in comparison to the conventional DSGW with a linear-shaped beam tunnel. Beam wave interaction simulations showed that the output power and the electronic efficiency, respectively, increased from ~420 W to ~580 W and from 7.0% to 9.3% at 240 GHz. These two kinds of DSGWs were fabricated by using the nanocomputer numerical control (CNC) milling and wire cutting techniques, and their performances were cold tested by using a vector network analyzer. The measurement results were in good agreement with the simulations and demonstrated that both the traditional and novel DSGWs achieved a wide frequency bandwidth of ~40 GHz (0.22–0.26 THz) with a transmission coefficient <inline-formula> <tex-math notation= LaTeX >${S}_{{21}}$ </tex-math></inline-formula> better than −2.7/−3.0 dB and a reflection coefficient <inline-formula> <tex-math notation= LaTeX >${S}_{{11}}$ </tex-math></inline-formula> lower than −13.0/−15.7 dB, respectively.