Nonlinear Equivalent-Circuit Model for Thin-Film Magnetic Material Based RF Devices

A nonlinear equivalent-circuit model is developed for thin-film magnetic material based RF devices such as frequency-selective Iimiter (FSL) and signal-to-noise enhancer (SNE). The ferromagnetic resonance is modeled by a RLC parallel circuit with parameters derived from Kittel's equations. The nonlinear effect in magnetic material is represented by a pendulum model that predicts cross-frequency coupling as well as parametric oscillations of spins. The coupling of spin waves in different orders is also modeled by coupled nonlinear pendulum resonators with the exchange coupling between the spins represented by coupling inductors. The measurement results of a FSL in literature are used as a reference, and the model successfully predicts the threshold power level, non-linear insertion loss, and frequency selectivity of the device.