Wide Band Interaction Impedance and Mode Excitation in Glide Symmetric Double Corrugated Waveguides for mm-Wave TWTs

• Published in: IEEE transactions on electron devices 2023-10, Vol.70 (10), p.1-8
• Main Authors: Castro, Nelson, Saavedra-Melo, Miguel, Rajo-Iglesias, Eva, Capolino, Filippo
• Format: Article
• Language: English
• Subjects: Backward waves; Brillouin zones; Corrugated waveguides; Dispersion; Double corrugated waveguide (DCW); Electric fields; Electromagnetic waveguides; Electron beams; glide symmetry; Harmonic analysis; Impedance; Millimeter waves; Periodic structures; slow wave structure (SWS); Symmetry; Traveling wave tubes; traveling wave tubes (TWTs); Traveling waves
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2023.3304278

Focusing on traveling wave tube (TWT) applications, the interaction impedance between an electron beam and electromagnetic modes in three distinct, but related, corrugated waveguides that operate at millimeter waves is investigated together with the role of glide symmetry. Two waveguide structures have glide symmetry, and the irreducible Brillouin zone (BZ) is related to half of the period, leading to a wide band linearity, i.e., nondispersive, property of the dispersion diagram. The investigation on the modes with longitudinal electric field that can be excited shows that the bottom-top glide (BT glide) symmetric corrugated waveguide has a wide band interaction impedance, hence it is a good candidate for millimeter wave TWT amplifiers. Furthermore, the backward electromagnetic mode in such BT glide slow wave structure (SWS) is not \textit{z} polarized, eliminating the risk of backward wave oscillations.