Coupling Electromagnetic Waves to Spin Waves: A Compact Model for Frequency Selective Limiters

Abstract

A nonlinear circuit model is developed for magnetic material based frequency-selective limiters (FSL). The dominant magnetic-behaviors of FSL devices are translated into equivalent circuits with parameters rigorously determined from fundamental physics. The spin motions as well as the ferromagnetic resonance (FMR) are modeled by RLC parallel circuits with parameters derived from Polder’s tensor and Kittel’s equations. The exchange coupling between spins is modeled by an inductor added between adjacent RLC circuits based on quantum spin theory. The nonlinear cross-frequency coupling from signal at ω to spin waves at ω/2 is represented by a pendulum model that predicts the parametric oscillations of spins. A FSL device described in literature is used as an example to validate the circuit model. The simulation results match the measurement results published, and the model successfully predicts the threshold power level, nonlinear insertion loss, time delay, and frequency selectivity of the device.