Metamaterial-Based Novel S-Band Coaxial Slow Wave Structure

In this article, a novel ${S}$ -band metamaterial-based coaxial slow wave structure (MCSWS) is proposed for high-power microwave (HPM) applications. The electromagnetic features of the proposed MCSWS and conventional coaxial slow wave structure (CCSWS) are investigated. The dispersion curve and coupling impedance of the two models have been compared to ascertain the advantages of MCSWS over CCSWS. For the same structural dimensions, the $\pi $ mode resonant frequency of the fundamental mode (TM00) of MCSWS is 2.49 GHz, whereas it is 3.82 GHz for the CCSWS. The coupling impedance of the MCSWS at its resonant frequency is $\sim 2000~\Omega $ , while it is $\sim 115~\Omega $ for the CCSWS. Furthermore, the transmission characteristics of the fabricated MCSWS have been measured with the help of Anritsu MS2037C VNA Master. The measured reflection coefficient confirms the operation of MCSWS at 2.48 GHz. Moreover, a magnetically insulated line oscillator (MILO) configured using the proposed MCSWS has been investigated in the presence of electron beams to predict its RF performance. The particle-in-cell simulation predicted an output power of 6 GW at a frequency of 2.4 GHz with a power conversion efficiency of 21%.