The Experts below are selected from a list of 13836 Experts worldwide ranked by ideXlab platform
M N Afsar - One of the best experts on this subject based on the ideXlab platform.
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precision measurement of Complex Permittivity and permeability by microwave cavity perturbation technique
International Conference on Infrared Millimeter and Terahertz Waves, 2005Co-Authors: Mi Lin, Yong Wang, M N AfsarAbstract:This paper demonstrates the precision measurement of Complex Permittivity and permeability of several dielectric and ferrite materials through microwave cavity perturbation technique. The measurement was performed at C, X, Ku, and K band four frequency ranges. The measured results are discussed and compared with the data published in the literature.
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Complex Permittivity and permeability of barium and strontium ferrite powders in x ku and k band frequency ranges
Journal of Applied Physics, 2005Co-Authors: Adil Bahadoor, Yong Wang, M N AfsarAbstract:This paper presents accurate results for the Complex Permittivity, e=e′−je″ and permeability, μ=μ′−jμ″ of barium ferrite powder (BaFe12O19) and strontium ferrite powder (SrFe12O19), in the frequency range from 8.0to26.5GHz. The Complex Permittivity and permeability are determined via the waveguide transmission/reflection (TR) technique and the waveguide cavity resonator (CR) technique at 25°C and relative humidity <75%. Measurements reveal that the real permittivities of BaFe12O19 and SrFe12O19 are, respectively, 2.497
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measurements of Complex Permittivity and permeability of common ferrimagnets at millimeter waves
IEEE Transactions on Magnetics, 2004Co-Authors: M N Afsar, Yong Wang, K M Lee, Karen KocharyanAbstract:In this paper, Complex Permittivity and permeability of several yttrium iron garnet (YIG) and hexagonal ferrite ceramics are investigated in a broad-band spectrum for the first time. The measurements were realized using a broad-band quasi-optical millimeter-wave (QOM) system with a backward-wave oscillator as the source of tunable coherent radiation. The dielectric and magnetic parameters of the ferrimagnets were obtained by fitting theoretical curves to the experimental spectra. Three types of YIG specimen were initially measured and compared to theoretical results, and then hexagonal ferrites were measured in the demagnetized state for the first time. It was shown that this method provides an accurate characterization of soft ferrites as well as hard anisotropic ferrites in the entire millimeter-wave range.
T C Goel - One of the best experts on this subject based on the ideXlab platform.
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Complex Permittivity Complex permeability and microwave absorption properties of ferrite polymer composites
Journal of Magnetism and Magnetic Materials, 2007Co-Authors: S M Abbas, Ratnamala Chatterjee, Anil Dixit, T C GoelAbstract:Abstract The Complex Permittivity ( e ′– je ″), Complex permeability (μ′– jμ ″) and microwave absorption properties of ferrite–polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2–12.4 GHz) frequency range. The M-type hexaferrite composition BaCo +2 0.9 Fe +2 0.05 Si +4 0.95 Fe +3 10.1 O 19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe +3 to Fe +2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured Complex Permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters e ′, e ″, μ′ and μ″ are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of −24.5 dB (>99% power absorption) at 12 GHz with the −20 dB bandwidth over the extended frequency range of 11–13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).
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Complex Permittivity and microwave absorption properties of a composite dielectric absorber
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: S M Abbas, Ratnamala Chatterjee, Mahesh Chandra, A Verma, T C GoelAbstract:Two types of composite samples were prepared using dielectric particulates such as BaTiO3, polyaniline and conducting carbon in polyurethane matrix. One of the composite samples contains synthesized BaTiO3 and polyaniline, while the other sample using, the commercial ingredients. Structural properties of both synthesized and commercial BaTiO3 and polyaniline have been investigated. Complex Permittivity ðe 0 � je 00 Þ and microwave absorption properties of the prepared composites were studied in X-band (8.2–13.5 GHz). An optimized composite sample with synthesized BaTiO3 and polyaniline has shown a maximum reflection loss of � 25 dB (>99% power absorption) at 11.2 GHz with a bandwidth (full frequency width at half of the maximum response) of 2.7 GHz in a sample thickness of 2.5 mm. The measured absorption values have been validated by theoretical calculations. Materials can find applications in suppression of electromagnetic interference (EMI) and reduction of radar signature. � 2005 Elsevier Ltd. All rights reserved.
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Complex Permittivity permeability and x band microwave absorption of cacoti ferrite composites
Journal of Applied Physics, 2000Co-Authors: Praveen Singh, V K Babbar, Archana Razdan, R K Puri, T C GoelAbstract:The effect of Co2+Ti4+ substitution on Complex permeability, Permittivity, and microwave absorption has been studied for [Ca(CoTi)xFe12−2xO19]96.0[La2O3]4.0 ferrite-epoxy composites, wherein x varies from 0 to 1.0 in steps of 0.2, in the frequency range from 8.0 to 12.4 GHz. The ferrites with x>0 exhibit significant dispersion in Complex Permittivity (e′−je″) with the maximum value of e″ observed for x equal to 0.2. The dispersion in Complex permeability (μ′−jμ″) is not significant. The variations of reflection loss and percentage absorption have been studied as a function of frequency, Co2+Ti4+ content, and thickness of the absorber. A maximum reflection loss of 31.0 dB is obtained for composites with x equal to 0.2 and absorber thickness of 2.5 mm. The experimental values of the matching frequency and the matching thickness agree well with the theoretical values obtained from an impedance-matching solution map.
Brian P Gaucher - One of the best experts on this subject based on the ideXlab platform.
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determination of the Complex Permittivity of packaging materials at millimeter wave frequencies
IEEE Transactions on Microwave Theory and Techniques, 2006Co-Authors: Thomas Zwick, A Chandrasekhar, Chris Baks, Ullrich R Pfeiffer, S Brebels, Brian P GaucherAbstract:The focus of this paper is the determination of the Complex Permittivity of chip packaging materials at millimeter-wave frequencies. After a broad overview of existing measurement techniques, three methods will be presented that have been established for the dielectric property determination of substrate, as well as mold materials (encapsulants, under-fill, etc.) in the millimeter-wave frequency range. First, the open resonator used here will be briefly described. It allows accurate determination of the dielectric constant and loss of thin sheet substrate materials from below 20 GHz to above 100 GHz. Second, a filled waveguide method is explained in detail. The setup used here can determine the Complex dielectric properties of mold materials from 70 to 100 GHz. Third, the method based on covered transmission lines will be described in detail. The used lines allow measurements from below 40 GHz to approximately 90 GHz. Verification of all three methods will be provided by inter-comparison and comparison to values from the literature. Additionally, results for several typical substrate and mold materials that are available for millimeter-wave packaging will be shown and discussed.
Ugur Cem Hasar - One of the best experts on this subject based on the ideXlab platform.
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Self-Calibrating Noniterative Complex Permittivity Extraction of Thin Dielectric Samples
IEEE Transactions on Electromagnetic Compatibility, 2018Co-Authors: Ugur Cem Hasar, Yunus KayaAbstract:A microwave method relying on uncalibrated scattering (S-) parameters is proposed to measure the Complex Permittivity ( $\varepsilon _r$ ) of thin dielectric samples. It has the following two main advantages. First, it takes into account effect of the sample holder, used for holding the sample, especially important for thin sample electromagnetic property characterization. Second, it does not require any specific information about the location of the sample (and its holder) inside its measurement cell for $\varepsilon _r$ extraction. For validation of our method, we applied a commercial three-dimensional electromagnetic simulation program—CST Microwave Studio—and the Lorentz dispersion model. Uncalibrated (as well as calibrated) S-parameter measurements were conducted to measure $\varepsilon _r$ of a 0.7 mm thick polyethylene sample (the sample holder was a 5.18 mm thick PVC sample) by our method and other similar methods in the literature. From the comparison, we observed that while the accuracy of tested methods significantly changed with inaccurate knowledge of the sample position inside its cell, the accuracy of our method did not much alter.
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a broadband and stable method for unique Complex Permittivity determination of low loss materials
IEEE Transactions on Microwave Theory and Techniques, 2009Co-Authors: Ugur Cem Hasar, C R WestgateAbstract:Transmission-reflection methods suffer from the increasing uncertainty in the phase of reflection scattering ( S-) parameter measurements of low-loss materials. In addition, transmission S -parameter measurements produce multiple solutions for the Complex Permittivity. In this paper, we propose a broadband and stable method for unique Complex Permittivity determination of low-loss materials by eliminating these problems. For elimination of the phase uncertainty problem, we utilize only the amplitudes of reflection S -parameters and Complex transmission S-parameters. In order to avoid multiple solutions, we express multivalued terms, which result in multiple solutions, in terms of single-valued terms. The method can work very well in limited frequency-band applications or for dispersive materials since it is based on point-by-point (or frequency-by-frequency) extraction. We measured the Complex Permittivity of two low-loss dielectric materials by different methods for validation of the method.
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thickness independent Complex Permittivity determination of partially filled thin dielectric materials into rectangular waveguides
Progress in Electromagnetics Research-pier, 2009Co-Authors: Ugur Cem HasarAbstract:A microwave method has been proposed for accurate Complex Permittivity measurement of thin dielectric materials partially fllling the waveguide. The method employs propagation constant measurements at two locations of the sample inside its holder. It increases the accuracy of Permittivity measurements of similar methods in the literature since it utilizes the measurements of the distances between the inner waveguide walls and sample lateral surfaces instead of directly measuring the sample thickness. It has been validated by comparing the measured Complex Permittivity of a thin Plexiglas sample by the proposed method with that of the method in the literature.
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a fast and accurate amplitude only transmission reflection method for Complex Permittivity determination of lossy materials
IEEE Transactions on Microwave Theory and Techniques, 2008Co-Authors: Ugur Cem HasarAbstract:Complex scattering parameter measurements using expensive vector network analyzers make microwave techniques inconvenient for industrial-based applications. In industry, accurate and fast evaluation of materials' properties using a relatively inexpensive measurement setup is a key issue. In this paper, we derive an objective function for fast and accurate Complex Permittivity (epsiv) determination of lossy materials using amplitude-only reflection and transmission scattering parameter measurements. The measurements can be carried out by relatively inexpensive microwave instruments such as a scalar network analyzer. The domain for computations of the epsiv is significantly reduced to facilitate rapid epsiv determination. The objective function is verified by measurements of a commercially available antifreeze solution and binary mixture of ethyl alcohol and water solution.
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two novel amplitude only methods for Complex Permittivity determination of medium and low loss materials
Measurement Science and Technology, 2008Co-Authors: Ugur Cem HasarAbstract:It is well known that there is no unique solution for Complex Permittivity determination of medium- and low-loss materials using amplitude-only measurements at one fixed frequency. In this paper, we propose two novel amplitude-only methods for one Complex Permittivity determination of these materials. The first method uses at least three amplitude-only measurements at different frequencies. For a change in Permittivity over frequency, we considered two different approximations (zero order and higher order). The second method utilizes amplitude-only measurements at critical frequencies which result in maximum or minimum amplitudes of scattering parameters. It is shown that at these frequencies, the expressions for scattering parameters simplify and then one Permittivity determination becomes possible. We derived two simple objective functions, which depend on only one variable, for the second method. In this sense, the second method greatly reduces the computation times for Permittivity determination. For validation of both methods, Complex scattering parameter measurements of two polytetrafluoro-ethylene (PTFE) and one soda-borosilicate glass (Corning 7750) samples fitted precisely into two waveguide holders are conducted at X-band (8.2–12.4 GHz), and their Complex permittivities are determined by different techniques.
Ratnamala Chatterjee - One of the best experts on this subject based on the ideXlab platform.
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Complex Permittivity permeability and wide band microwave absorbing property of la3 substituted u type hexaferrite
Journal of Magnetism and Magnetic Materials, 2010Co-Authors: R S Meena, Sudeshna Bhattachrya, Ratnamala ChatterjeeAbstract:Abstract Polycrystalline samples of U-type hexaferrite series: (Ba 1−3 x La 2 x ) 4 Co 2 Fe 36 O 60 with 0.10≤ x≤ 0.20 in step of 0.05, are prepared by conventional solid state reaction route. Partial substitution of Ba 2+ ions with La 3+ ions enhances the electron hopping and reduces the magnetic interaction in the samples over the entire X-band frequencies; leading to wide band microwave absorption in all sample. Relative Complex Permittivity ( e r = e ′− je ″) and permeability ( μ r = μ ′− jμ ″) of the prepared samples were measured using Vector Network Analyzer (VNA, Agilent PNA-L N5230A) for X-band (8.2–12.4 GHz) frequency range. The maximum absorption of 99.8% was obtained for x =0.10 sample for thickness t m =1.8 mm and all sample showed absorption ≥96%. The reflection loss ( R L ) calculated using the measured parameter (e r = e ′− je ″ and μ r = μ ′− jμ ″) shows good agreement when compared with the return loss measured directly using VNA for sample x =0.20. The material can be expected to find relevance in suppression of electromagnetic interference (EMI) shielding and reduction of radar signatures.
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Complex Permittivity Complex permeability and microwave absorption properties of ferrite polymer composites
Journal of Magnetism and Magnetic Materials, 2007Co-Authors: S M Abbas, Ratnamala Chatterjee, Anil Dixit, T C GoelAbstract:Abstract The Complex Permittivity ( e ′– je ″), Complex permeability (μ′– jμ ″) and microwave absorption properties of ferrite–polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% in polyurethane (PU) matrix have been investigated in X-band (8.2–12.4 GHz) frequency range. The M-type hexaferrite composition BaCo +2 0.9 Fe +2 0.05 Si +4 0.95 Fe +3 10.1 O 19 was prepared by solid-state reaction technique, whereas commercial PU was used to prepare the composites. At higher GHz frequencies, ferrite's permeabilities are drastically reduced, however, the forced conversion of Fe +3 to Fe +2 ions that involves electron hopping, could have increased the dielectric losses in the chosen composition. We have measured Complex Permittivity and permeability using a vector network analyzer (HP/Agilent model PNA E8364B) and software module 85071. All the parameters e ′, e ″, μ′ and μ″ are found to increase with increased ferrite contents. Measured values of these parameters were used to determine the reflection loss at various sample thicknesses, based on a model of a single-layered plane wave absorber backed by a perfect conductor. The composite with 80% ferrite content has shown a minimum reflection loss of −24.5 dB (>99% power absorption) at 12 GHz with the −20 dB bandwidth over the extended frequency range of 11–13 GHz for an absorber thickness of 1.6 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).
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Complex Permittivity and microwave absorption properties of a composite dielectric absorber
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: S M Abbas, Ratnamala Chatterjee, Mahesh Chandra, A Verma, T C GoelAbstract:Two types of composite samples were prepared using dielectric particulates such as BaTiO3, polyaniline and conducting carbon in polyurethane matrix. One of the composite samples contains synthesized BaTiO3 and polyaniline, while the other sample using, the commercial ingredients. Structural properties of both synthesized and commercial BaTiO3 and polyaniline have been investigated. Complex Permittivity ðe 0 � je 00 Þ and microwave absorption properties of the prepared composites were studied in X-band (8.2–13.5 GHz). An optimized composite sample with synthesized BaTiO3 and polyaniline has shown a maximum reflection loss of � 25 dB (>99% power absorption) at 11.2 GHz with a bandwidth (full frequency width at half of the maximum response) of 2.7 GHz in a sample thickness of 2.5 mm. The measured absorption values have been validated by theoretical calculations. Materials can find applications in suppression of electromagnetic interference (EMI) and reduction of radar signature. � 2005 Elsevier Ltd. All rights reserved.