Topic
Dielectric loss
About: Dielectric loss is a research topic. Over the lifetime, 20296 publications have been published within this topic receiving 349254 citations.
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01 May 1979
TL;DR: In this article, an improvement to a recently reported theory for the analysis of the pattern and impedance loci of microstrip antennas is developed, which yields a theory which is simple and inexpensive to apply.
Abstract: : An improvement to a recently reported theory for the analysis of the pattern and impedance loci of microstrip antennas is developed. It yields a theory which is simple and inexpensive to apply. The fields in the interior of the antennnas are characterized in terms of a discrete set of modes. The poles corresponding to these modes are complex and depend on the losses in the antenna. The representation of the fields in terms of these modes in rigorous only for a bona fide cavity with no copper loss. The proper shift in the complex poles due to the addition of copper and radiative losses is approximated by lumping the latter two together with the dielectric loss to form an effective loss tangent. By so doing, it is found that the resulting expressions for impedance of the microstrip antenna is in good agreement with measured results for all modes and feed locations. The theory is applied to the evaluation of impedance variation with feed location, multiport analysis, and to design of circularly polarized microstrip antennas. (Author)
556 citations
TL;DR: In this article, the dielectric properties at microwave frequencies of Ba(Zn1/3Ta2/3)O3 ceramics prepared by sintering were investigated.
Abstract: The dielectric properties at microwave frequencies of Ba(Zn1/3Ta2/3)O3 ceramics prepared by sintering were investigated. These ceramics had lower density but higher loss quality than ceramics hot-pressed at 1400°C. Loss quality was greatly improved by prolonged sintering. The Q of the ceramics measured by the dielectric resonator method was 14 000 at 12 GHz. The ceramics were investigated by X-ray diffraction analysis. It was found that Q improvement corresponds with increased Zn and Ta ordered structures in the ceramics.
549 citations
TL;DR: In this article, a cubic framework of amorphous carbon and uniformly dispersed core-shell Fe@graphitic carbon nanoparticles is used to construct a high-performance microwave absorber.
Abstract: Composites of magnetic metal nanoparticles and carbon materials are highly desirable for high-performance microwave absorbers due to their compatible dielectric loss and magnetic loss abilities. In this article, novel nanocomposites, Fe/C nanocubes, have been successfully prepared through an in situ route from a metal–organic framework, Prussian blue, by controlled high-temperature pyrolysis. The resultant nanocubes are actually composed of a cubic framework of amorphous carbon and uniformly dispersed core–shell Fe@graphitic carbon nanoparticles. Within the studied pyrolysis temperature range (600–700 °C), the porous structure, iron content, magnetic properties, and graphitization degree of the Fe/C nanocubes can be well modulated. Particularly, the improved carbon graphitization degree, both in amorphous frameworks and graphitic shells, results in enhanced complex permittivity and dielectric loss properties. The homogeneous chemical composition and microstructure stimulate the formation of multiple dielectric resonances by regularizing various polarizations. The synergistic effect of dielectric loss, magnetic loss, matched impedance, and dielectric resonances accounts for the improved microwave absorption properties of the Fe/C nanocubes. The absorption bands of the optimum one obtained at 650 °C are superior to most composites ever reported. By considering the good chemical homogeneity and microwave absorption, we believe that the as-fabricated Fe/C nanocubes will be promising candidates as highly effective microwave absorbers.
545 citations
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TL;DR: In this paper, expressions for the conductor loss in microstrip transmission lines are derived for rutile and alumina substrates, taking into account the finite thickness of the strip conductor and apply to the mixed dielectric system.
Abstract: Expressions are derived for the conductor loss in microstrip transmission lines. The formulas take into account the finite thickness of the strip conductor and apply to the mixed dielectric system. Good agreement with experimental data is obtained for rutile and alumina substrates.
543 citations
TL;DR: In this article, the present state of knowledge of the chemistry, structure, and dielectric properties of these materials, as well as examples of our own work, are described and compared.
Abstract: Dielectric ceramic materials have been studied for decades due
to both their application in important technologies and the fundamentally
interesting relationships among their crystal chemistry, crystal structures,
and physical properties. Recent dramatic changes in microelectronics and in
particular wireless communications technologies have made the importance of
materials with the unusual combination of high dielectric constant, low dielectric
loss and low temperature dependence of dielectric constant of great interest.
In this review, the present state of knowledge of the chemistry, structure,
and dielectric properties of these materials, as well as examples of our own
work, are described.
528 citations