Design and Cold Test Study of W-band Suspended Multi-Channel Array Integrated Microstrip Meander Line Traveling-wave tubes

This paper introduces a wide-cathode suspended multi-channel array microstrip meander line slow-wave structure (WC-SMCA-MML SWS) for high power traveling-wave tubes (TWTs). Evolved from a conventional single-channel S-MML SWS design, the structure integrates four unit cells via an on-chip four-channel power divider within a shared cavity, establishing fully coupled slow-wave channels. Excitation is provided by a single, large-aspect-ratio cathode, which harnesses the longitudinal electric field generated through inter-channel coupling to enhance beam-wave interaction. Particle-in-cell (PIC) simulations compare the saturated performance of three configurations: the proposed single-beam WC-SMCA-MML TWT, a four-independent-beam SMCA-MML TWT, and a conventional single-channel S-MML TWT. Under a beam voltage of 7.8 kV, a current density of 200 A/cm², and an interaction length of 9.0 mm, the four-beam configuration yields a saturation output power at 96 GHz that is 3.47 times greater than the conventional TWT, with an 11.8% gain improvement. The single-beam WC-SMCA-MML TWT further surpasses the four-beam version, achieving 30.18% higher saturation power and a 12.7% gain increase while maintaining a 3-dB bandwidth of 91–99 GHz. At 95 GHz with a 2 W input, it delivers 55.42 W output power and 14.42 dB gain, improvements of 25.07% in power and 7.21% in gain over the four-beam design. A prototype fabricated via photolithography exhibits a reflection coefficient S11 < -14.5 dB and transmission coefficient S21 between − 4.5 dB and − 6.2 dB across 90–100 GHz, closely matching simulations and validating the design for efficient, integrated high-power TWT applications.