Cold Circuit Analysis of a Coupled-Cavity Slow Wave Structure for Mm-Wave TWT

An equivalent circuit approach for the analysis of cold circuit parameters such as dispersion and interaction impedance characteristics was used for the design of staggered double slot square-shaped coupled-cavity slow wave structure at millimeter waveband and the results were validated against numerical analysis at Ka-band and W-band. The derived lumped parameters of the square-shaped coupled-cavity slow wave structure (CC-SWS) is different from the reported cylindrical CC-SWS. A typical structure was fabricated at Ka-band and cold test measurement was carried and the results were compared against the proposed equivalent circuit approach. The comparison of results shows that the equivalent circuit is simple but accurate to predict within 3% and 10% accuracy against numerical simulation and cold test measurement for dispersion and interaction impedance characteristics, respectively.