CAD of an X-band TWT interaction circuit with experimental validation

In this paper we present results obtained while testing the 3D electromagnetic solver CST Microwave Studio as a CAD tool in the design of some parts of the beam-wave interaction circuit of an X-band traveling-wave tube. A pair of impedance transformers, present in the input and output microwave ports of the interaction circuit, was characterized by simulating and measuring its voltage stand wave ratio. The interaction circuit based on a ring-bar slow-wave structure was simulated using both the eigenmode and the frequency domain solvers of the CST Microwave Studio. The phase velocity and the interaction impedance, also named ¿cold parameters¿, were simulated by direct and indirect methods and the results compared to experimental ones.