10 results on '"Le Floc'h, Marcel"'
Search Results
2. Automatic measurement of complex tensorial permeability of magnetized materials in a wide microwave frequency range
- Author
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Queffelec, Patrick, Mallegol, Stephane, and Le Floc'h, Marcel
- Subjects
Ferrites (Magnetic materials) -- Testing ,Microwave measurements -- Methods ,Permeability -- Measurement ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper describes a microwave measurement technique enabling the automatic and broad-band determination of the complex permeability tensor components [mu] [kappa] of magnetized materials. The method is applicable to ferrites, as well as magnetic composite materials. The measurement cell is composed of a nonreciprocal strip transmission line partly filled with the sample that is to be characterized. The data-processing program based on a quasi-static approach is valid whatever the magnetization state of the material is from the total demagnetization state to the saturation. The scattering matrix of the cell is measured in a wide frequency range (130 MHz-6 GHz) with a network analyzer setup. The stripline is set in the air gap of an electromagnet to magnetize the material. The electromagnetic parameters of the sample under test are deduced from the scattering matrix using analytical relations. General equations for [mu] and [kappa] are proposed. Some measurements of magnetized ferrites are reported and compared with values predicted by Polder's relations to validate the technique in the saturation state. To our knowledge, this is the first noniterative measurement method giving [mu] and [kappa] simultaneously in a wide range of frequency. Index Terms--Anisotropic media, ferrites, microwave measurements, permeability measurement.
- Published
- 2002
3. Extension of the effective medium approximation for determination of the permeability tensor of unsaturated polycrystalline ferrites
- Author
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Bariou, David, Queffelec, Patrick, Gelin, Philippe, and Le Floc'h, Marcel
- Subjects
Anisotropy -- Evaluation ,Ferrites (Magnetic materials) -- Evaluation ,Permeability -- Evaluation ,Business ,Electronics ,Electronics and electrical industries - Abstract
This paper presents a physical model of the properties of polycrystalline ferrites below magnetic saturation, a common condition in many applications of ferrites in microwave devices. The properties are mainly characterized through the elements of the effective permeability tensor as functions of magnetization state, anisotropy field, and frequency. Partially magnetized states are characterized by a suitable distribution of magnetic domains over orientations. The magnetic domain shapes studied were cylinders and spheres. Homogeneity of the medium is obtained in the effective medium approximation, which allows us to treat heterogeneous magnetic materials as a function of the volume fraction of nonmagnetic matter present in the material. The model gives all the components of the permeability tensor in a single calculation phase. The paper presents results for different partially magnetized states at remanence (with no external field applied) and compares them with empirical formulations of permeability tensor components, in their domain of validity. Index Terms--Anisotropic media, ferrimagnetic materials, ferrites, permeability.
- Published
- 2001
4. Nonreciprocal cell for the broad-band measurement of tensorial permeability of magnetized ferrites: direct problem
- Author
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Queffelec, Patrick, Le Floc'h, Marcel, and Gelin, Philippe
- Subjects
Magnetization -- Research ,Ferrites (Magnetic materials) -- Research ,Permeability -- Research ,Anisotropy -- Research ,Waveguides -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
In this paper, a broad-band characterization method for measuring the complex permeability tensor components and complex scalar permittivity of magnetized ferrites is described. The technique is based on the reflection/transmission measurement of a rectangular waveguide partly filled with the ferrite that is to be characterized. The fundamental principle of the measurement consists in using the anisotropy of the material to lead to the nonreciprocity of the device in order to have the same number of measurable parameters (the S-parameters of the cell) for the characteristics we want to determine. Here, we will recall the principle of the mode-matching method used for the electromagnetic analysis of the cell (direct problem). We will bring to the fore the difficulties linked to the determination of the complex propagation constants of the different modes and will present a calculation procedure that makes this determination in a wide-frequency range easier. We will then compare at X-band frequencies (8-12 GHz) the theoretical S-parameters with those measured for ferrites of well-known properties in order to validate the direct problem. The determination of the permittivity and permeability values from the measured parameters (inverse problem) is not addressed here. Index Terms - Anisotropic media, ferrites, microwave measurements, permeability measurement, waveguide discontinuities.
- Published
- 1999
5. Broad-band characterization of magnetic and dielectric thin films using a microstrip line
- Author
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Queffelec, Patrick, Le Floc'h, Marcel, and Gelin, Philippe
- Subjects
Thin films -- Analysis ,Permeability -- Analysis ,Mensuration -- Usage ,Strip transmission lines -- Usage ,Dielectric films -- Analysis - Published
- 1998
6. A Broadband Permeameter for 'in situ' Measurements of Rectangular Samples
- Author
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Salahun, Erwan, Queffelec, Patrick, Le Floc'h, Marcel, and Gelin, Philippe
- Subjects
Magnetic materials -- Analysis ,Thin films -- Magnetic properties ,Microwave devices -- Design and construction ,Business ,Electronics ,Electronics and electrical industries - Abstract
The measurement method presented here permits the determination of the complex permeability [Mu]* and permittivity [Epsilon]* of rectangular samples of various thicknesses (0.1 [micro]m-1800 [micro]m) over the (130 MHz-7 GHz) frequency band. This method is based on the S-parameters measurements of an asymmetrical stripline containing the sample under test. It does not require any magnetic reference sample. The originality of this method is to reproduce the same environment for the material under test as encountered in microwave devices. The results given by this 'in situ' measurement technique are more useful to design microwave devices than those given by traditional measurement methods. Index Terms--Magnetic materials, permeability measurement, stripline, thin films.
- Published
- 2001
7. New Method for Determining the Permeability Tensor of Magnetized Ferrites in a Wide Frequency Range
- Author
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Queffelec, Patrick, Le Floc'h, Marcel, and Gelin, Philippe
- Subjects
Ferrites (Magnetic materials) -- Heat treatment ,Waveguides -- Analysis ,Permeability -- Measurement ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
To provide a broad-band method for measuring the complex permeability tensor components of magnetized ferrites we have realized a nonreciprocal rectangular waveguide cell. A network analyzer setup is used to measure the scattering parameters of the cell over a wide range of frequencies. The nonreciprocity of the cell permits the determination of the permeability tensor components in a single experimental phase. Complex permittivity and complex components of the permeability tensor are computed from a data-processing program, taking into account higher order modes excited at the cell discontinuities and using a numerical optimization procedure to match calculated and measured values of the S-parameters. We have studied the convergence of the calculated S-parameters as the number of modes taken into account in the calculations. Sensitivity to the input parameters for the optimization algorithm is discussed. A thru-reflect-line calibration in conjunction with a specific sample holder is used to eliminate systematic errors inherent in the S-parameter measurements. Measured complex permeability tensor components data for microwave ferrites are presented at X-band frequencies (8-12 GHz). Experimental results are in good agreement with theoretical results given by the ferromagnetic material theory. Index Terms--Anisotropic media, ferrites, inverse problem, microwave measurements, permeability measurement, waveguides.
- Published
- 2000
8. Propriétés hyperfréquences de matériaux composites à base de poudres de ferrites doux
- Author
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Chevalier, Alexis, Mattei, Jean-Luc, Le Floc'H, Marcel, Lab-STICC_UBO_MOM_MF, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Electronique et Systèmes de Télécommunications (LEST), Université de Brest (UBO)-Ecole Nationale Supérieure des Télécommunications de Bretagne-Centre National de la Recherche Scientifique (CNRS), and Chevalier, Alexis
- Subjects
[SPI.ELEC]Engineering Sciences [physics]/Electromagnetism ,[SPI.ELEC] Engineering Sciences [physics]/Electromagnetism ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,[PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,[SPI.TRON] Engineering Sciences [physics]/Electronics ,[SPI.TRON]Engineering Sciences [physics]/Electronics - Abstract
Nous présentons un modèle capable de prédire l'évolution statique et dynamique de la susceptibilité magnétique des matériaux composites isotropes en fonction de la concentration. Ce modèle simple s'appuie sur deux paramètres scalaires. Le premier est la susceptibilité intrinsèque i qui ne dépend que de la composition chimique de la poudre utilisée et dont la valeur se rapproche de celle de la susceptibilité rotationnelle. Le second est le coefficient effectif de forme N, rendant compte de l'aspect hétérogène de la matière et des effets démagnétisants; sa valeur est inférieure à 1/3 et dépend de la concentration en matière magnétique.
- Published
- 1998
9. Influence des contraintes de matriçage sur la fréquence de gyrorésonance dans les matériaux composites à base de ferrites doux
- Author
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Chevalier, Alexis, Le Floc'H, Marcel, Chevalier, Alexis, Lab-STICC_UBO_MOM_MF, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Electronique et Systèmes de Télécommunications (LEST), and Université de Brest (UBO)-Ecole Nationale Supérieure des Télécommunications de Bretagne-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[SPI.ELEC]Engineering Sciences [physics]/Electromagnetism ,[SPI.ELEC] Engineering Sciences [physics]/Electromagnetism ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,[PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,[SPI.TRON] Engineering Sciences [physics]/Electronics ,[SPI.TRON]Engineering Sciences [physics]/Electronics - Abstract
La fréquence de résonance dans les matériaux composites à base de poudre magnétique tend vers la fréquence de résonance naturelle de spin pour des concentrations bien inférieures à l'unité. Nous avons montré comment une méthode simple permet de s'affranchir des contraintes d'origine technologique, souvent incontrôlées dans les matériaux sensibles aux effets magnétoélastiques. Cette méthode permet de remonter à la fréquence de résonance naturelle de spin et ainsi de déterminer le champ effectif d'anisotropie.
- Published
- 1998
10. Caractérisation et application de matériaux composites nanostructurés à la réalisation de dispositifs hyperfréquences non réciproques
- Author
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Mallégol, Stéphane, Laboratoire d'Electronique et Systèmes de Télécommunications (LEST), Université de Brest (UBO)-Ecole Nationale Supérieure des Télécommunications de Bretagne-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne occidentale - Brest, Le Floc'h Marcel, and Mallégol, Stéphane
- Subjects
paramètres S ,[SPI.OTHER]Engineering Sciences [physics]/Other ,Anisotropie magnétique induite ,[SPI.OTHER] Engineering Sciences [physics]/Other ,caractérisation hyperfréquence ,métallurgie des poudres ,isolateur ,composite magnétique ,tenseur de perméabilité ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,non réciprocité ,[PHYS.COND] Physics [physics]/Condensed Matter [cond-mat] ,nanoparticules - Abstract
Anisotropic properties of magnetized ferrites are commonly at the basis of nonreciprocity in microwave devices, e.g., circulators and isolators. However, ferrites are not the best suited materials for such applications, due to their moderate saturation magnetization and high-sintering temperature needed during their manufacturing process. Consequently, research laboratories tend to propose substitute materials. To achieve an optimized performances-nonreciprocal device based on such a magnetized material, the exact knowledge of its tensorial permeability is required over a broad-frequency range. The originality of this work is twofold. At first, a measurement technique enabling the noniterative and broad-band (up to 6-7 GHz) determination of the permeability tensor components (µ, k) of magnetized or demagnetized magnetic materials has been developed. The measurement cell used is composed of a nonreciprocal strip transmission line. The major advantage of this new technique is to permit to study the material behavior in the same environment as microwave devices (« in-situ » characterization method). Then, the measurement capability has been employed to demonstrate the field-induced anisotropy of nanocomposite samples. Based on a comparison with a standard ferrite, this original magnetic anisotropy of magnetized nanophases has been exploited to investigate the design of an optimum an low-cost resonance microwave isolator., Aux fréquences micro-ondes, les ferrites sont caractérisés par une perméabilité tensorielle, représentative de leur anisotropie induite sous champ magnétique. Cette propriété spécifique est à l'origine du comportement non réciproque de dispositifs comme les circulateurs et les isolateurs. Les limitations des milieux ferrites (aimantation à saturation réduite, fortes températures de frittage lors de leur élaboration) conduisent cependant les laboratoires à étudier des matériaux s'y substituant. Pour pouvoir réaliser des fonctions hyperfréquences non réciproques optimisées à partir de tels matériaux, la mesure préalable de leur tenseur de perméabilité est requise sur une large bande de fréquences. L'originalité du travail présenté dans ce mémoire est double : - dans un premier temps, une technique de mesure non itérative des éléments (µ, k) du tenseur de perméabilité des milieux magnétiques, dans un état quelconque d'aimantation, a été développée. Elle est utilisable du continu jusqu'environ 6 à 7 GHz, selon le type de matériau testé. Outre la détermination analytique de (µ, k) en fonction des paramètres S de la cellule de mesure en ligne de transmission élaborée, son principal intérêt est de permettre d'étudier le matériau dans des conditions voisines de celles fixées par l'application en technologie planaire ultérieure (mesure « in-situ »), - à partir de cette technique de caractérisation expérimentale, les propriétés d'anisotropie induite de matériaux composites nanostructurés aimantés ont ensuite été démontrées puis ajustées pour mettre en œuvre un isolateur hyperfréquence à résonance. Les performances de ce dernier sont au moins comparables à celles des isolateurs à ferrites, pour une quantité de matière magnétique moindre.
- Published
- 2003
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