Transient Nonlinear-Loss Responses of Ferrite Microstrip Structures to High-Power Microwave Pulses Under Perpendicular-Pumping Configuration

A theoretical and experimental investigation of the threshold and loss responses of nonlinear (NL) loss effects in ferrite microstrip structures excited by high-power microwave (HPM) pulses under a perpendicular-pumping configuration is studied. Based on the coupling dynamics between the uniform precession mode and parametrically excited half-frequency spin-wave pairs, a pulse duration$\tau $-dependent critical threshold model$h_{c}^{\bot }(\tau)$is developed. In addition, an equivalent simulation method for NL power loss under above-threshold excitation is developed in polycrystalline yttrium iron garnet (YIG) substrate. This method enables the power dissipation along the transmission path and the evolution of the radio frequency (RF) magnetic field to be evaluated in commercial full-wave electromagnetic simulators. Experimental and simulation results at 9.6GHz indicate that, when$\tau $is shorter than 100ns, the threshold power exhibits an approximate inverse dependence on$\tau $, consistent with the short-pulse energy-threshold behavior expected from classical transient parametric-excitation theory. For a given incident power, a higher threshold leads to weaker achievable NL loss. Increasing the YIG substrate thickness reduces the internal RF magnetic-field intensity, thereby significantly increasing the threshold power and weakening the loss capability. Specifically, for$\tau = 200$ns, the threshold power of a 0.5-mm-thick sample is about 14.5times larger than that of a 0.3-mm-thick sample, while the NL loss at an incident power of approximately 600W is reduced by about 5dB. The good agreement between simulations and measurements demonstrates that the proposed method can quantitatively characterize transient NL loss behavior of ferrites under a perpendicular-pumping configuration.