A broadband permeability measurement method based on the full-wave electromagnetic (EM) analysis of a non-reciprocal transmission line is presented. The dispersion diagram for the first significant modes inside the ferrite loaded section of the line is obtained. The presence of magnetostatic modes generated by the magnetized ferrite inside the line is verified. Using a mode matching technique, the theoretical scattering parameters (S-parameters) of the transmission line are calculated. The fullwave analysis is validated with measurements of material properties in limit cases.