Design and RF Characterization of High-Power Ferrule-Loaded Folded Waveguide SWS for mm-Wave TWT

Design and analysis of ferrule-loaded folded waveguide slow wave structure is carried out for a high-power millimeter-wave traveling-wave tube (TWT). The design of the structure is carried out by numerical simulation. A typical structure has been designed and fabricated at the Ka-band, and cold test measurement is carried out for the cold circuit parameters and the results are compared against numerical analysis. To compare the efficacy of the ferrule-loaded folded waveguide structure, a conventional folded waveguide structure is also designed for the same operating bandwidth, and cold circuit parameters are compared. The comparison results shows that the interaction impedance of the ferrule-loaded folded waveguide structure is double compared with the conventional structure at the cost of reduction in cold bandwidth. Furthermore, particle-in-cell (PIC) simulation is also carried out to estimate the output power and gain for both the structures for the same operating band, and the results are compared. The comparison results show that the cross section is reduced by 22% and the overall interaction length is reduced by 50% for the ferrule-loaded FW-SWS compared with the conventional FW-SWS for the same output power of about 500 W.