A Low-Voltage W-Band TWT Employing Dual-Sheet Beam and a CSRR-Based Slow Wave Structure

This letter presents a novel low-voltage W-band traveling wave tube (TWT) based on a metamaterial-inspired slow wave structure (SWS). The proposed design integrates complementary split-ring resonators (CSRRs) within a square waveguide, achieving an interaction impedance exceeding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.82~\Omega $</tex-math> </inline-formula> and a normalized phase velocity around 0.203 from 92 to 96GHz. A probe-fed coupler and dual-sheet beam configuration are employed to enhance coupling efficiency and output power. Cold test measurements reveal a return loss better than −14 dB and insertion loss (IL) below 5.5 dB. Particle-in-cell simulations predict a saturated output power of 322.6 W, gain of 35.03 dB, and RF efficiency of 6.7% at 94GHz under a beam voltage of 12.05 kV and current of 200 mA. These results highlight the potential of this compact structure as a high-efficiency millimeter-wave source suitable for the next-generation wireless communication systems.