Parametric modeling of folded waveguide circuits for millimeter-wave traveling wave tubes

Summary form only given. Results of different models are compared for calculating effective phase velocities and interaction impedances of folded waveguide slow wave circuits for use in millimeterwave and submillimeter-wave traveling wave tubes. These parameters are needed for 1D parametric model simulations of folded waveguide traveling wave tubes (FWTWTs). The models investigated include approximate analytic expressions, equivalent circuits, three-dimensional (3D) finite difference models, and 3D finite element models. The phase velocity predictions are compared with experimental measurements of dispersion in a 40-55 GHz folded waveguide circuit. The various model results are incorporated into the CHRISTINE1D code to obtain predictions of small signal gain and saturated power in a 40-55 GHz, 100 W FWTWT. The comparisons of CHRISTINE1D simulations and measured frequency-dependent gain provide a sensitive, confirming assessment of the accuracy of the simulation tools.