An intercomparison of techniques for measuring dielectric permittivity and loss over a wide frequency range

Dielectric properties of Eucalyptus urophylla wood were measured by using a network analyzer over an ultrawide frequency range between 0.2 GHz and 20 GHz. The effects of moisture content (MC), temperature and frequency on the dielectric permittivity and the dielectric loss factor of Eucalyptus urophylla were investigated along different grain directions. The results showed that the dielectric permittivity along with the dielectric loss factor increased significantly with the elevation in MC. At the frequency of 2380 MHz with the MC increasing from 0% to 100%, the dielectric permittivity along different grain directions (including longitudinal, radial and tangential directions) increased by 180%, 110% and 112%, respectively, while the loss factor along these three directions increased by 1642%, 3703% and 5058%, respectively. In addition, the increase in dielectric properties of Eucalyptus urophylla wood was determined with the temperature elevating. When the temperature elevated from 20 °C to 140 °C, the dielectric permittivity at 2380 MHz along the longitudinal, radial and tangential directions, increased by 19%, 14% and 15%, respectively, while the loss factor increased by 133% at most. As the radio frequency increased, the dielectric permittivity of wood decreased. Regression equations satisfactorily described the dielectric properties of wood along different grain directions with different moisture contents.

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Permittivity and Loss of Composites of Epoxy Resin and Kevlar Fibres

Advanced Composites Letters ◽

10.1177/096369359500400405 ◽

1995 ◽

Vol 4 (4) ◽

pp. 096369359500400 ◽

Cited By ~ 1

Author(s):

G.M. Tsangaris ◽

G.C. Psarras

Keyword(s):

Dielectric Permittivity ◽

Epoxy Resin ◽

Filler Content ◽

Low Frequency ◽

Interfacial Polarization ◽

Dielectric Behaviour ◽

Frequency Range ◽

Wide Range ◽

Dielectric Permittivity And Loss

The dielectric behaviour of composites with epoxy resin and kevlar fibres is investigated in a wide range of frequency and temperature. Dielectric permittivity is increasing with filler content and temperature, being always higher in the low frequency range. Dielectric permittivity and loss of the composites is mostly affected by interfacial polarization arising from inhomogeneities at interfaces introduced by the filler.

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Microstructure and Electrical Properties of Calcium Copper Titanate Ceramics

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.551 ◽

2007 ◽

Vol 561-565 ◽

pp. 551-555 ◽

Cited By ~ 1

Author(s):

Lai Jun Liu ◽

Hui Qing Fan

Keyword(s):

Electrical Properties ◽

Dielectric Permittivity ◽

High Frequency ◽

Low Frequency ◽

Wide Frequency Range ◽

Frequency Range ◽

Cell Parameters ◽

Grain Sizes ◽

Calcium Copper Titanate ◽

Titanate Ceramics

The effect of stoichiometry, i.e. Ca/Cu ratios (CaCu3xTi4O12, x = 0.8, 0.9, 1.0, 1.1 and 1.2) on the microstructure and electrical properties was investigated. The grain sizes of CaCu3xTi4O12 composition increased sharply with the increase of copper, from ~1 μm with x = 0.8 to ~50 μm with x = 1.2. The real part of dielectric permittivity changed dramatically, the pellet with x = 1.0 had the highest dielectric permittivity ~160, 000 at 1 kHz. Furthermore, the dielectric permittivity of all pellets was impressively large values (between 10, 000 to 1, 000,000 at 100 Hz) and was nearly constant over a wide frequency range between 100 Hz to ~100 MHz. However, the dielectric permittivity of CaCu3xTi4O12 composition is not consistent with the amount of copper and cell parameters and grain sizes. Impedance spectroscopy exhibited that the CaCu3xTi4O12 composition had two semicircle at least at high frequency (~ 107 Hz) and low frequency (<100 Hz), respectively. The grain and grain boundary of the compositions had different impedance and relaxation behavior.

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Simulation of electromagnetic field distribution in the measuring cell for determining the dielectric permittivity of materials at microwave frequencies

Doklady BGUIR ◽

10.35596/1729-7648-2020-18-6-75-80 ◽

2020 ◽

Vol 18 (6) ◽

pp. 75-80

Author(s):

N. A. Pevneva ◽

A. A. Kopshai ◽

A. L. Gurskii

Keyword(s):

Electromagnetic Field ◽

Dielectric Permittivity ◽

Theoretical Calculations ◽

Three Dimensional ◽

Wide Frequency Range ◽

Frequency Range ◽

Polyethylene Tube ◽

Dielectric Parameters ◽

Measuring Cell ◽

Ansoft Hfss

To determine the dielectric permittivity of materials in a wide frequency range with the automation of measurements and the necessary accuracy, measuring cells have been created to ensure the simplicity of the design of the waveguide path. In order to obtain information about the suitability of measuring cells based on irregular SHF waveguides for estimation of dielectric parameters of materials, we simulated the structure of electromagnetic field in the system consisting of two irregular waveguides and waveguide chamber placed between them using a three-dimensional electrodynamic simulation in Ansoft HFSS package environment. The distribution of the electric field was simulated when an empty polyethylene tube, a rod of fluoroplastic and a rod of textolite are placed in the measuring cell. It was demonstrated that high order modes fade out in irregular waveguide and do not affect the precision of obtained results, and significant edge effects were not detected. It allows one to utilize measuring cells based on irregular waveguides together with a scalar or vector network analyzer and using the partial filling of the waveguide method or the modified Nicholson – Ross – Weir method for measurements of dielectric permittivity  of materials. The results of modeling the dependence of the amplitude and phase of the reflection coefficient of the textolite and fluoroplastic on the frequency in Ansoft HFSS environment are given. The simulation results are compared with the results obtained experimentally. The frequency dependencies of  were obtained experimentally for test materials – textolite and fluoroplastic – in the frequency range of 25,95–37,50 GHz. The experimental data are in satisfactory agreement with the results of theoretical calculations and do not go beyond the boundaries specified by the measurement uncertainty.

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Electromagnetic Properties of Carbon Gels

Materials ◽

10.3390/ma12244143 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4143 ◽

Cited By ~ 1

Author(s):

Jimena Castro-Gutiérrez ◽

Edita Palaimiene ◽

Jan Macutkevic ◽

Juras Banys ◽

Polina Kuzhir ◽

...

Keyword(s):

Electrical Conductivity ◽

Dielectric Permittivity ◽

Low Frequency ◽

Microwave Frequency ◽

Power Laws ◽

Wide Frequency Range ◽

Electromagnetic Properties ◽

Frequency Range ◽

Carbon Gels ◽

Electrical Conductivities

The electromagnetic properties of various carbon gels, produced with different bulk densities, were investigated in a wide frequency range (20 Hz–36 GHz). The values of dielectric permittivity and electrical conductivity at 129 Hz were found to be very high, i.e., more than 105 and close to 100 S/m, respectively. Both strongly decreased with frequency but remained high in the microwave frequency range (close to 10 and about 0.1 S/m, respectively, at 30 GHz). Moreover, the dielectric permittivity and the electrical conductivity strongly increased with the bulk density of the materials, according to power laws at low frequency. However, the maximum of microwave absorption was observed at lower densities. The DC conductivity slightly decreased on cooling, according to the Arrhenius law. The lower activation energies are typical of carbon gels presenting lower DC electrical conductivities, due to a higher number of defects. High and thermally stable electromagnetic properties of carbon gels, together with other unique properties of these materials, such as lightness and chemical inertness, open possibilities for producing new electromagnetic coatings.

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Investigation on the Microwave Properties of Kenaf and Rice-Husk Fiber Reinforced Pla Composite Utilizing One-Port Coaxial Transmission Line Reflection Method

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.471-472.868 ◽

2011 ◽

Vol 471-472 ◽

pp. 868-873 ◽

Cited By ~ 4

Author(s):

Nor'aini Ahmad Zawawi ◽

Alyani Ismail ◽

Abdan Khalina ◽

Mohd Adzir Mahdi

Keyword(s):

Dielectric Permittivity ◽

Rice Husk ◽

Loss Tangent ◽

Wide Frequency Range ◽

Microwave Properties ◽

Equal Weight ◽

Frequency Range ◽

Weight Percentage ◽

Plastic Composites ◽

Tan Δ

The paper investigates the microwave properties of natural fiber reinforced biodegradable plastic composites in order to recognize their potential as alternatives to common printed circuit board (PCB) for electronic communication industries. Thus, the paper reports on measured dielectric properties for two new composites under study: Kenaf/Poly Lactic Acid (PLA) and rice husk/PLA and their results are compared. The sample is made from equal weight percentage loading (50%wt - 50%wt) of kenaf and PLA. Another sample has also equal weight percentage loading (50% wt - 50%wt) of rice husk and PLA. The complex dielectric permittivity (ε = ε' – jε'') and loss tangent (tan δ) of the two samples of natural fibers plastic composites have been studied in the frequency range of 500 MHz to 10 GHz. The dielectric permittivity is measured by scattering parameter (S-parameter) using a Vector Network Analyzer (VNA). The concentration dependence of permittivity and loss tangent is analyzed for each sample. It is observed that from 500 MHz to 3.32 GHz, real permittivity (ε') values are consistent throughout the wide frequency range, at approximately 3.3. However, the permittivity seems to decrease at higher frequencies starting from 3.35 GHz for both samples, down to 2.5 at 10 GHz. Measured results show that kenaf/PLA mixture has higher permittivity (ε') than the rice husk/PLA composite across the wide frequency range. Meanwhile, loss tangent (tan δ) is low and remains similar for both types of fiber compositions.

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