Design RF Magnetic Devices With Linear and Nonlinear Equivalent Circuit Models: Demystify RF Magnetics With Equivalent Circuit Models

Magnetic materials offer a unique combination of properties for RF applications, such as nonreciprocity, high permeability, broad tunability, strong frequency dispersion, and nonlinearity [1], [2], [3]. In contrast to a dielectric material, where a scalar permittivity constant is often sufficient to represent the property of the material, the permeability of an RF magnetic material is usually a tensor in its linear regime, which is expressed in the form of an asymmetrical matrix; yet each entry in the matrix varies as a function of frequency and biasing field. At high RF power, the magnetic material can be easily driven into a nonlinear regime, which exhibits increased dissipation, drifting of resonant frequency, generation of harmonics, and so on. At a microscale, electromagnetic waves in magnetic materials are often coupled with spin waves that are supported by exchange coupling in quantum mechanics, which adds more complexity to the understanding and applications of the material.