Topic
Electrical impedance
About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.
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TL;DR: In this paper, the influence of hindered water removal from a polymer electrolyte fuel cell under constant load was investigated using electrochemical impedance spectroscopy, where the cathodic gas outlet of the cell was closed and impedance measurements were performed at periodic time intervals.
Abstract: The influence of hindered water removal from a polymer electrolyte fuel cell under constant load was investigated
using electrochemical impedance spectroscopy. The cathodic gas outlet of the cell was closed and impedance
measurements were performed at periodic time intervals. Under the experimental conditions, the investigated
system is far from steady-state conditions. It is shown that enhanced mathematical techniques are required for
evaluation of the impedance data obtained. These techniques, the time course interpolation as well as
the Z-HIT refinement, lead
to quasi-causal spectra which are well
interpreted by means of the porous electrode model.
83 citations
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TL;DR: In this article, the impedance and dielectric properties of Ag/Al2O3 composites are investigated experimentally in the frequency range from 100 MHz to 1 GHz, and equivalent circuit analysis and numerical simulations are carried out.
Abstract: The impedance and dielectric properties of Ag/Al2O3 composites are investigated experimentally in the frequency range from 100 MHz to 1 GHz. Besides, equivalent circuit analysis and numerical simulations were carried out. For the composites with sufficiently high silver loading, current paths were formed and negative permittivity appeared. The negative permittivity can be well described by lossy Drude model. Moreover, the negative permittivity sample manifests inductive characteristic and shunt inductors are added to its equivalent circuit. Numerical simulations show that the interconnection of silver particles results in negative permittivity, hence the serious attenuation of electromagnetic waves.
83 citations
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30 Jul 1985
TL;DR: In this paper, a moisture-insensitive system adapted to couple radio frequency energy at a low impedance from a matched two conductor transmission line, through a vehicle windshield and to an antenna in a manner which minimizes stray radio frequency radiation within the passenger compartment of the vehicle.
Abstract: The present invention is a moisture-insensitive system adapted to couple radio frequency energy at a low impedance from a matched two conductor transmission line, through a vehicle windshield and to an antenna in a manner which minimizes stray radio frequency radiation within the passenger compartment of the vehicle. The system includes two pair of conducting plates, one pair mounted on each side of the windshield, each pair opposite the other pair. A coaxial feed line is coupled to the inside pair of plates and a matching circuit is connected across the outside pair of plates. A full-size, unloaded antenna element is connected to the output of the matching circuit. A decoupling device, such as a decoupling sleeve or a RF choke, can be used to minimize RF current flow on the shield conductor of the coaxial feed line. The coaxial cable is coupled directly through the windshield, without an intervening matching network, so that RF energy at a low impedance is coupled to the outside pair of plates. This low impedance minimizes parasitic coupling of the feed system to moisture on the windshield, windshield wipers and other foreign bodies. The elements of the invention cooperate to minimize the level of stray radiation within the passenger compartment of the vehicle and provide, in the illustrated embodiment, a 2.0:1 VSWR bandwidth that extends from 830 to 880 megahertz.
83 citations
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TL;DR: In this article, a set of impedance values given either experimentally or heuristically for implementation as a time-domain impedance-equivalent boundary condition (TDIBC) is discussed.
Abstract: The modeling of a set of impedance values given either experimentally or heuristically for implementation as a time-domain impedance-equivalent boundary condition (TDIBC) is discussed. It is shown that impedance as defined by the reflection of plane harmonic waves when extended for broadband time-domain applications can correspond to mathematically feasible but physically unacceptable noncausal reflection processes. Given a set of impedance data on a finite, positive, and real frequency range, it is possible to construct causal time-domain models that render efficient implementation of TDIBC for broadband reflections. However, these models defined by measurement of harmonic waves may not be valid for the reflection of impulses, for which measurement of transient reflections is warranted.
83 citations
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21 May 1998
TL;DR: In this article, the placement of signal traces on a two-sided printed circuit board such that impedance of the traces is controlled and so that the number of power and ground pins required on an integrated circuit are minimized.
Abstract: The present invention relates to the placement of signal traces on a two-sided printed circuit board such that impedance of the traces is controlled and so that the number of power and ground pins required on an integrated circuit are minimized.
83 citations