Ferrite transmission lines (FTL) are capable of sharpening the rise time of gas switching triggers by gradually saturating the core under high voltage pulse excitation. The current design of FTL relies on engineering experience and lacks relevant theoretical basis and numerical simulation methods. In this paper

a numerical simulation method for FTL field-circuit coupling based on the nonlinear characteristics of magnetic cores is proposed. Firstly

the mechanism of rise time sharpening due to FTL core magnetization is theoretically analyzed

then the magnetization of ferrite cores for characterized the nonlinear properties of the cores is experimentally tested. Thus

the simulation model of FTL field-circuit coupling is built based on core nonlinear characteristics. On this basis

the magnetization curve is extrapolated by segmental fitting to obtain the magnetization curve at a high frequency to improve the accuracy of the model. Finally

the simulation model is used to analyze the correspondence between the core magnetization process and pulse sharpening as well as the pulse sharpening law. The simulation results show that FTL output rise time decreases with increasing input voltage amplitude

and decreases with increasing length of transmission line. However

the length of the transmission line is too long for the rise time to continue to decrease. And the output pulse voltage amplitude decreases due to the increase in loss.