Practical Aspects of the Characterization of Ferrite Absorber Using One-port Device at RF Frequencies (original) (raw)
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Journal of Applied Physics, 2013
This paper describes the experimental results obtained by a broadband permeability measurement method based on the full-wave electromagnetic (EM) analysis of a non-reciprocal transmission line. The method offers a new experimental tool for measuring the broadband dynamic behavior of ferrites whatever their magnetization state. The methodology and experimental setup are presented with the aim of extracting both the permittivity and the two components (diagonal l and off-diagonal j) of the permeability tensor. Experimental data on commercial ferrites set in different magnetization states are presented and discussed. Furthermore, this method opens perspectives for the determination of other useful magnetic parameters such as resonance linewidth DH. This quantity can be then measured at different frequencies, where conventional resonant methods give a value at a fixed frequency. V C 2013 AIP Publishing LLC. [http://dx.
Parameters Extraction of Ferrite EMI Suppressors for PCB Applications Using Microstrip Test Fixture
IEEE Transactions on Magnetics, 2010
The goal of this work was to investigate the behavior of a ferrite electromagnetic interference (EMI) suppressor when placed in a real surrounding. Electrical parameter measurements of the same EMI suppressor can differ for different combination of instruments and test fixtures. For that reason specially designed microstrip test fixtures are developed for the vector network analyzer (VNA) measurements. This paper describes the measurement technique, parameters extraction, and characterization of ferrite EMI suppressors for printed circuit board (PCB) applications. Two commercially available components, multilayer chip SMD inductors in a ferrite body, are measured and characterized using a VNA E5071B and developed adaptation test fixture on PCB board. These measurements describe intrinsic and extrinsic parameters of the components and their behavior. If the components are mounted on the PCB, i.e., in a real environment, then the two-port EMI suppressor model with extrinsic parameters has to be used at RF frequencies. The comparison of measured and datasheet values is further presented.
IEEE Transactions on Magnetics, 2005
Mn-Zn ferrite cores present high permeability within the kilohertz-to-megahertz frequency range. They also present high permittivities within the same frequency range. High permeabilities lead to significant permittivity measurement errors when the conventional two-parallel-electrode method is used. In contrast, high permittivities result in the deviations of measured permeabilities from their intrinsic values. This paper presents a field-circuit coupled method to study each of these two phenomena by examining a ferrite toroid with rectangular cross section. The same toroid is used to construct an inductor and a capacitor, respectively. Analytical expressions for electric and magnetic fields in, and complex power supplied to the inductor and capacitor are formulated. Results are obtained, which show that the measured permeabilities and permittivities for Mn-Zn ferrites deviate from their intrinsic values significantly. A Newton-Raphson method is then introduced to determine the intrinsic permeabilities and permittivities based on their measured values.
IEEE Transactions on Electromagnetic Compatibility, 2000
A methodology to efficiently design products based on magneto-dielectric (ferrite) materials with desirable frequency responses that satisfy electromagnetic compatibility and signal integrity requirements over RF and microwave bands is presented here. This methodology is based on an analytical model of a composite magneto-dielectric material with both frequency-dispersive permittivity and permeability. A procedure for extracting complex permittivity and permeability of materials from experimental data is based on transmission line measurements. The genetic algorithm is applied for approximating both permittivity and permeability of materials by series of Debye frequency dependencies, so that they are represented as "double-Debye materials" (DDM). The DDM is incorporated in the finite-difference time-domain numerical codes by the auxiliary differential equation approach.
Elektron, 2018
An implementation of the transmission/reflection line method is presented to determine the intrinsic electromagnetic properties of unknown materials with a relative permeability not equal to one. A low-cost, easy to manufacture sample holder is realised using a coaxial transmission line with N-type female connectors. The reflection and transmission coefficients are measured to simultaneously extract the electric permittivity and magnetic permeability. The classic Nicolson-Ross-Weir (NRW) extraction technique in frequency domain is presented such that the equations can be easily implemented with open-source tools such as GNU Octave. The shift in phase reference planes and connector calibration measurements are performed such that a lowcost vector network analyser (VNA) without de-embedding function can be used. The measurement procedure is valid from 2 MHz to 6 GHz. The article also comments on the sample preparation especially the thickness of the material slab.
IEEE Transactions on Magnetics, 2000
This paper explores an influence of conductive layer geometry on electrical parameters of ferrite electromagnetic interference (EMI) suppressor, which consists of conductive layer in ferrite monolithic structure. Near ferrimagnetic resonant frequency, component has maximal impedance and efficiently suppresses noise. In order to achieve better suppression (i.e., larger impedance), conductive layers should be longer. Nevertheless, longer conductive lines introduce parasitic capacitance, which causes the maximal impedance frequency shift. Because of that, the frequency range where component can be used for efficient EMI suppression is shifted towards lower frequencies, and designing process should be very careful. In this paper, we present simulation of frequency dependent impedance for different geometry parameters of conductive layer. Results for the inductance and the maximal impedance frequency shift of the proposed EMI suppressors are presented in the range 1 MHz-3 GHz. Proposed EMI suppressors were experimentally tested using Agilent 4287A RF LCR meter. Comparison of simulated and measured values of impedance shows a good agreement.
Journal of Applied Physics, 2010
In this paper, a full band microwave isolator constructed from an array of metal wire-coated ferrite samples is presented. Here, the magnetic permeability of the metamaterialized structure is controlled by a relatively weak external magnetic field. The tunable permeability of the ferrites in this experiment allows us to create unidirectional wave propagation through the structure over the entire X-band frequency spectrum. The analysis presented here takes into account potential surface plasmon modes generated between the gaps of metal wires when the external magnetic field is applied. Here, we present a modification of the traditional transmission-reflection measurement method by normalizing the transmission and reflection coefficients. This modification removes the occurrence of atypical phenomena for negative imaginary components of permeability and permittivity that arises in the measurement of metamaterials. Our modified method precisely determines the refractive index, impedance, permittivity, and permeability of both traditional reciprocal networks as well as nonreciprocal networks, such as the one presented here.
Method of Measuring Permittivity of Composite Materials with Hexagonal Ferrite Inclusions
2007 IEEE International Symposium on Electromagnetic Compatibility, 2007
A new simple method for measuring complex permittivity of substantially lossy composite materials is presented. In this method, a sample of the material under study should completely fill in the cross-section of the single-mode transmission line (waveguide), and the length of the sample must be an integer of a half-wavelength in the waveguide filled with this material. The oscillator frequency is swept linearly, the minima of the reflection coefficient are measured, and then analytical formulas are used to calculate real and imaginary parts of permittivity. The method was tested on magnetodielectric samples containing hexagonal ferrite powders, as well on such dielectric materials, as PMMA, schungite composites, and alabaster. This method can be a useful technique for measuring dielectric properties of absorbing materials designed, for example, for electromagnetic shielding purposes.
Journal of Magnetism and Magnetic Materials, 2011
The effect of Mg 2 + , Co 2 + and Ti 4 + substitution on microwave absorption has been studied for BaMg 0.5 Co 0.5 Ti 1.0 Fe 10 O 19 ferrite-acrylic resin composite in frequency range from 13 to 20 GHz. X-ray diffraction (XRD), scanning electron microscopy (SEM), vector network analysis and vibrating sample magnetometry (VSM) were employed to analyze structure, electromagnetic and microwave absorption properties of prepared ferrite. The obtained results of reflectivity demonstrate that by varying matching thickness along with weight percentage of ferrite to acrylic resin, the bandwidth coupled with reflection loss values of prepared composites can be easily tuned. Based on microwave measurement on reflectivity, it is found that BaMg 0.5 Co 0.5 Ti 1.0 Fe 10 O 19 is a good candidate for wideband electromagnetic compatibility and other practical applications at high frequency.