Modeling of Serpentine Waveguide Traveling Wave Tube to Calculate Gain Diagram

We develop an analytical model for traveling wave tubes (TWTs) amplifiers based on the serpentine waveguide (SW). This analytical model is a generalization of the Pierce model, assuming one-dimensional electron flow along a dispersive slow-wave structure (SWS), with space-charge effects accounted for. The cold structure parameters, i.e., phase velocity and characteristic impedance, are accounted for in the equivalent circuit model. We use the relation between characteristic and interaction impedance with an extra correction factor that accounts for the non-uniform beam-wave interaction over the interaction area. Particle-in-cell (PIC) simulation results are compared to the calculated gain versus frequency using the proposed model, revealing excellent agreement over a wide frequency range.