A method to measure wideband permeability was developed for 5-mm-square magnetic thin film from 0.1 to 10GHz by using a shielded short-circuited microstrip line as the test fixture. The S11 parameters of the test fixturewere measured with a vector network analyzer (VNA). The permeability was derived, based on the lumped element approximation, by comparing S11s with S11os 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 e caused by the substrate by comparing S11o of blank fixture with S11os 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.

The wideband measurement system of ΔH ω , FMR (ferromagnetic resonance) line width of microwave ferrite, is proposed. In this system, an all shielded shorted microstrip line is used as a test fixture and a specimen is inserted close to the short end. The absorption curve of FMR is observed by monitoring S11 of fixture and sweeping frequency in VNA (vector network analyzer) under constant external magnetic field. From these data, the frequency width Δω, at which an imaginary part μ" of complex permeability becomes half of maximum at resonance, is derived based on lumped element circuit model and ΔH is calculated by ΔH[Oe]=Δω[MHz]/2.8. As this ΔH is different from conventional ΔH, this is designated ΔH ω . The wideband measurement result of ΔH ω for 5mm square garnet slab over from 0.7[GHz] to 11[GHz] using just one test fixture is reported.

The use of short-and open-circuited transmission lines is widely known to be a simple method of measuring the permeability and permittivity of magnetic materials. Lumped element approximation is one of the methods to analyze these transmission lines. However, this approximation generally involves rather large model errors. We describe here a way to reduce these errors. The distributed element expression of short-and open-circuited transmission lines is expanded by a Taylor series, and the first and the second terms are adopted in a limited form. These analyses have clarified that this approximation could hold within  5% of model error if a phase shift l is less than 90% of /2 (1.4 radian), where  is the propagation constant and l is the sample length.

The wideband measurement system of permeability for magnetic thin slab was proposed for up to 10GHz, using the all shielded shorted microstrip lines. In order to analyze this configuration, the reference plane was set on the other end of specimen where the LC parallel resonant circuit was assumed. The permeability was derived from the measurement of S11 by VNA (Vector Network Analyzer) comparing between with strong static magnetic field parallel to rf magnetic field and without it. The shorted microstrip line was calibrated by the standard sample of rectangular shape NSS (Noise Suppression Sheet) comparing with the results of toroidal core measured by the shorted coaxial line.

In this paper, the reflection characteristics from low loss permittivity plate which is smaller than wavelength are discussed using the FDTD method. As the results, it is validated that the FDTD method is effective for the analysis on the reflection characteristics of a small size specimen. The effect of estimating permittivity using small size specimen by free-space method is discussed.