Search

This paper describes a mathematical model enabling the calculation of the effective permeability tensor of heterogeneous magnetic materials set in various magnetization states. The theoretical approach we propose permits to predict the microwave behavior of unsaturated magnetic loaded composites as well as those of unsaturated polycrystalline ferrites. The model gives all the complex components of the permeability tensor in a single calculation phase whatever the magnetization state of the material is. This is useful for the computer-aided design of microwave magnetic devices. The calculation of the effective permeability tensor is carded out from a limited number of parameters: saturation magnetization, anisotropy field, damping factor, external dc field strength, concentration, and shape of the magnetic particles or domains. The model is predictive in the way that the magnetization state of the material is determined from the strength of the external dc magnetic field applied on the material. [ABSTRACT FROM AUTHOR]

The topic of this paper is the study of electrically tunable phase-shifters based on the use of liquid crystals. The dielectric characterization of the commercial liquid crystal involved in this study allows us to determine its dielectric permittivities (with and without DC voltage applied) and then its dielectric anisotropy. In this way, two phase-shifter configurations were studied. Every devices propose inverted microstrip line. The two circuits have been realized with coplanar accesses to be use in the millimeter-frequency range. With the aim to improve the phase shift parameter (in °/GHz/cm), our work aims to reduce the transmission line. Instead of a rectilinear transmission line, this one is based on a symmetric stub line. The phase shift obtained is enhanced from 0.87°/GHz/cm to 2.77°/GHz/cm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 338–341, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20463 [ABSTRACT FROM AUTHOR]