Permeability Measurements of Magnetic Thin Films using Shielded Short-Circuited Microstrip Lines

摘要

??A method to measure wideband permeability was developed for 5-mm-square magnetic thin film from 0.1 to 10 GHz by using a shielded short-circuited microstrip line as the test fixture. The S _(11) parameters of the test fixture were measured with a vector network analyzer (VNA). The permeability was derived, based on the lumped element approximation, by comparing S _(11s) with S _(11os) which corresponded to without and with a strong magnetic field parallel to the microwave magnetic field caused by the microstrip line. In this case, the influence of substrate on which the thin film prepared could not be neglected due to the small gap between the microstrip line and the substrate. We introduced a method to derive an effective permittivity ε_(e) caused by the substrate by comparing S _(11o) of blank fixture with S _(11os) of fixture with sample under a strong static magnetic field. We also propose a method of determining whether the lumped element approximation is valid or not.