1D-FDTD Simulation of Microwave Generation Using Ferrite Electromagnetic Shock Lines

Abstract

Ferrite-charged nonlinear transmission lines (NLTLs) have been used as electromagnetic shock lines in applications that require pulses with extremely fast rise times. Subject to an intense external magnetic field (20–40 kA/m), these lines can generate microwave radiation generally in L-band (1–2 GHz) and are known in this case as nonlinear gyromagnetic lines. Due to its wide applicability in the RF area, such as electronic warfare (in defense) or high power beam modulators (in industry), there is growing interest in the study of these lines, especially using finite difference time domain (FDTD) simulations to predict some important line parameters, such as the rise time of the output pulse and the frequency generated. The FDTD method is based on the nonlinear behavior of the magnetic material that fills the line as the current pulse propagates, inducing RF oscillations due to the precession of the ferrite's magnetic moments, described mathematically by the Landau-Lifshitz-Gilbert equation (LLG). Thus, this work presents a one-dimensional numerical modeling and simulation (1D) study to describe the behavior of these lines, which operate in the TEM mode. The numerical simulations were obtained using the joint solution of the transmission line equations and the gyromagnetic LLG equation in the publicly available software OCTAVE.