Research Interests: Cryogenics, Materials Science, Q factor, Polyethylene, Temperature measurement, and 13 moreDielectric Loss, Dielectric Loss Tangent, High Density Concrete, High Density Polyethylene, Polytetrafluoroethylene, Material Properties, Dielectric Materials, Electrical And Electronic Engineering, Dielectric Losses, Resonant Frequency, Permittivity, High density, and Low loss
Overview of frequency domain measurement techniques of the complex permittivity at microwave frequencies is presented. The methods are divided into two categories: resonant and non-resonant ones. In the first category several methods are... more
Overview of frequency domain measurement techniques of the complex permittivity at microwave frequencies is presented. The methods are divided into two categories: resonant and non-resonant ones. In the first category several methods are discussed such as cavity resonator techniques, dielectric resonator techniques, open resonator techniques and resonators for non-destructive testing. The general theory of measurements of different materials in resonant structures is presented showing mathematical background, sources of uncertainties and theoretical and experimental limits. Methods of measurement of anisotropic materials are presented. In
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Research Interests: Materials Science and AIP
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The impurity paramagnetic ion, Cu2+ substitutes Al in the SrLaAlO4 single crystal lattice, this results in a CuO6 elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The... more
The impurity paramagnetic ion, Cu2+ substitutes Al in the SrLaAlO4 single crystal lattice, this results in a CuO6 elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The aggregate frequency width of the electron spin resonance with the required minimum level of impurity concentration has been evaluated in single crystal SrLaAlO4 at 20 millikelvin. Measured parallel hyperfine constants, A∥Cu, were determined to be -155.7 × 10-4 cm-1, - 163.0 × 10-4 cm-1, - 178.3 × 10-4 cm-1 and - 211.1 × 10-4 cm-1 at 9.072 GHz (WGH4,1,1) for the nuclear magnetic quantum number MI = + 3/2 , + 1/2 , - 1/2 , and- 3/2 respectively. The anisotropy of the hyperfine structure reveals a characteristics of static Jahn-Teller effect. The second-order-anisotropy-term, ∼ {(spin-orbit coupling)/10Dq}^2 is significant and can not be disregarded, with the local strain dominating over the observed Zeeman-anisotropy-energy dif...
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Single crystal materials exhibit much lower dielectric losses then their ceramic counterparts. In this paper computed properties of high Q dielectric resonators which can be made of different single crystal materials are presented. Such... more
Single crystal materials exhibit much lower dielectric losses then their ceramic counterparts. In this paper computed properties of high Q dielectric resonators which can be made of different single crystal materials are presented. Such resonators can operate at low temperatures ...
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A procedure to determine accurately the unloaded Q-factor, resonant frequency and coupling coefficients of a dielectric resonator in the transmission mode has been developed. The technique is based on a derived equation relating S21 and... more
A procedure to determine accurately the unloaded Q-factor, resonant frequency and coupling coefficients of a dielectric resonator in the transmission mode has been developed. The technique is based on a derived equation relating S21 and QL, measurements of $1,
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A method of measuring all the complex permeability tensor components of microwave ferrites using a single cylindrical ferrite sample is described. Two dielectric ring resonators having the same height and internal diameter but different... more
A method of measuring all the complex permeability tensor components of microwave ferrites using a single cylindrical ferrite sample is described. Two dielectric ring resonators having the same height and internal diameter but different external diameters, operating on HE111± and H011 modes respectively, are applied for these measurements. Permeability tensor components are computed from the measured resonant frequencies and Q
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Yttrium Vanadate (YVO4) is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of the YVO4 are not known, we measured the... more
Yttrium Vanadate (YVO4) is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of the YVO4 are not known, we measured the complex permittivity at the frequency of 25 GHz, using the Hakki-Coleman dielectric resonator technique in the temperature range from 13 K to 80 K. The real part of relative permittivity of YVO4 turned out to be similar to that of Sapphire - one of popular dielectric materials, used at microwave frequencies. The measured loss tangent tang {\delta} of the YVO4 was of the order of 10^(-6) at cryogenic temperatures. As Yttrium Vanadate (YVO4) is easy to synthesis and machine, it may replace the expensive Sapphire in some microwave applications.
... Technology, 9 1751-1756, 1998. [6] B. Riddle, J. Baker-Jarvis, and J. Krupka, Complex Permittivity Measurements of Common Plastics over Variable Temperatures, IEEE Trans. on Microwave Theory Tech, MTT-51 727-733,2003. ...
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Abstract Quasi TE011 mode cavity and split post dielectric resonator have been used to measure resistivity of very thin gold films deposited on single crystal quartz substrates. It has been found that a sharp transition of electrical... more
Abstract Quasi TE011 mode cavity and split post dielectric resonator have been used to measure resistivity of very thin gold films deposited on single crystal quartz substrates. It has been found that a sharp transition of electrical properties takes place for films of thickness between ...
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ABSTRACT The properties of metamaterials are now being investigated in a number of research centres. Structures such as split-ring resonators (SRR) have been developed to produce negative index materials (NIMs). Liquid crystals absorb... more
ABSTRACT The properties of metamaterials are now being investigated in a number of research centres. Structures such as split-ring resonators (SRR) have been developed to produce negative index materials (NIMs). Liquid crystals absorb over a broad range of wavelengths and have refractive indices which are extremely sensitive to temperature and external electromagnetic fields. Liquid crystals are therefore promising for the dynamic control of permittivity in metamaterials. A thermally controlled metamaterial structure employing a nematic liquid crystal (1801) has been characterised. It has been shown that using such liquid crystals in an anisotropic medium to construct useful materials, tunability of the effective parameters can be achieved. Measurements were performed at around 4.9 GHz.
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ABSTRACT Split dielectric resonators operating in a quasi-TE011 mode were used for the measurement of the complex permittivity and the complex permeability of planar metamaterials deposited on low-loss dielectric substrates at microwave... more
ABSTRACT Split dielectric resonators operating in a quasi-TE011 mode were used for the measurement of the complex permittivity and the complex permeability of planar metamaterials deposited on low-loss dielectric substrates at microwave frequencies. Separation of the complex permittivity from the complex permeability for a specific metamaterial was achieved by performing measurements of the resonance frequencies and the Q-factors of a split post-dielectric resonator with two samples having different diameters but identical patterns. Measurements of the resonance frequencies and the Q-factors of empty substrates served as reference materials to determine the resonance frequency shifts and Q-factor changes due to the presence of the metamaterial only. The effective complex permittivity and permeability were determined on the basis of accurate electromagnetic modeling of the resonance structures containing the samples.
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Yttrium Vanadate is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of YVO 4 are not known, we measured the complex... more
Yttrium Vanadate is a birefringent crystal material used in optical isolators and circulators with potentials for application in cryogenic microwave devices. As microwave properties of YVO 4 are not known, we measured the complex permittivity at frequency of 25 GHz using the ...
Abstract - MgF2 is a hard and birefringent crystal with low refractive index and a wide transmission range and is widely used in prisms and optical windows. The RF and microwave losses of Magnesium Fluoride (MgF2) crystal are low as... more
Abstract - MgF2 is a hard and birefringent crystal with low refractive index and a wide transmission range and is widely used in prisms and optical windows. The RF and microwave losses of Magnesium Fluoride (MgF2) crystal are low as compared to other fluorides but not well investigated. ...
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We provide an overview of two nondestructive techniques, the split-post and split-cylinder resonator, which are under consideration as standard test methods for measuring the relative permittivity and loss tangent of bare low-temperature... more
We provide an overview of two nondestructive techniques, the split-post and split-cylinder resonator, which are under consideration as standard test methods for measuring the relative permittivity and loss tangent of bare low-temperature cofired ceramic (LTCC) substrates over the frequency range of 1–30 GHz. The capabilities and limitations of the split-post and split-cylinder resonator are outlined, and the level of agreement between the two techniques is examined through comparison of the relative permittivity and loss tangent measurements of a fused silica and an LTCC substrate.
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Fabrication of dielectric materials with low losses at microwave frequencies and stable dielectric properties under varying temperatures is an important and challenging area of research. In this paper characterisation of several planar... more
Fabrication of dielectric materials with low losses at microwave frequencies and stable dielectric properties under varying temperatures is an important and challenging area of research. In this paper characterisation of several planar dielectrics at microwave frequencies (~9.5 GHz) in the temperature range from 20 K to 290 K using a split post dielectric resonator has been presented. We have compared temperature stability of measured dielectric properties of RT5880, RT6010, LTCC, FR4 and Ba(MgxTay)O3 materials. Presented results are useful for selection of a material suitable for a specific application.
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