Nonreciprocal cell for the broad-band measurement of tensorial permeability of magnetized ferrites: Direct problem

In this paper, a broad-band characterization method For measuring the compl ex permeability tensor components and complex scalar permittivity of magnet ized ferrites is described. The technique is based on the reflection/transm ission measurement of a rectangular waveguide partly filled with the ferrit e that is to be characterized. The fundamental principle of the measurement consists in using the anisotropy of the material to lead to the nonrecipro city of the device in order to have the same number of measurable parameter s (the S-parameters of the cell) for the characteristics we want to determi ne. Here, we will recall the principle of the mode-matching method used for the electromagnetic analysis of the cell (direct problem). We will bring t o the fore the difficulties linked to the determination of the complex prop agation constants of the different modes and will present a calculation pro cedure that makes this determination in a wide-frequency range easier. We w ill then compare at S-band frequencies (8-12 GHz) the theoretical S-paramet ers with those measured for ferrites of well-known properties in order to v alidate the direct problem. The determination of the permittivity and perme ability values from the measured parameters (inverse problem) is not addres sed here.