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, an efficient method has been developed for the application of the surface acoustic impedance condition in time-domain solutions of aeroacoustic problems, such as the broadband-frequency simulation of a flow-impedance tube.
126 citations
TL;DR: In this paper, the impedance matching of the classic printed circular disc UWB monopole is improved by introducing transitions between the microstrip feed line and the printed disc and two particular designs are examined using a dual and single microstrip transition.
Abstract: Circular disc monopole antennas are investigated for current and future ultrawideband (UWB) applications. The studied antennas are compact and of small size (25 mm × 35 mm × 0.83 mm) with a 50-Ω feed line and offer a very simple geometry suitable for low cost fabrication and straightforward printed circuit board integration. More specifically, the impedance matching of the classic printed circular disc UWB monopole is improved by introducing transitions between the microstrip feed line and the printed disc. Two particular designs are examined using a dual and single microstrip transition. By using this simple antenna matching technique, respective impedance bandwidths (|Sn | <; -10 dB) from 2.5 to 11.7 GHz and 3.5 to 31.9 GHz are obtained. Results are also compared to a classic UWB monopole with no such matching network transitions. Measured and simulated reflection coefficient curves are provided along with beam patterns, gain and group delay values as a function of frequency. The transient behavior of the studied antennas is also examined in the time domain.
126 citations
TL;DR: In this paper, a planar scalar impedance holographic metasurface is designed at a dominant TM surface wave mode frequency, which is capable of beam forming with a desired electric field polarization and high gain.
Abstract: This paper presents the design of a novel planar scalar impedance holographic metasurface, which is capable of beam forming with a desired electric field polarization and high gain. It is demonstrated that the surface can be constructed with patches of simple geometry and design. A detailed analysis of the mechanism of scalar impedance holographic metasurfaces is discussed. The scalar impedance holographic metasurface is designed at a dominant TM surface wave mode frequency. It is observed that the TM surface wave mode has an impurity of TE polarized electric fields of small magnitude. The presence of this impurity is exploited to design a holographic metasurface for beam forming with a desired polarization. This modified-HAIS is capable of forming a beam at a nonphase crossover frequency, unlike the conventional HAIS. The design procedure of the surface, with simulation and measurement results, is presented.
126 citations
TL;DR: The proposed procedure of calibrated complex impedance measurements and dielectric quantification with scanning microwave microscopy is simple and fast and the accuracy of the results is not affected by varying stray capacitances.
Abstract: We present a procedure for calibrated complex impedance measurements and dielectric quantification with scanning microwave microscopy. The calibration procedure works in situ directly on the substrate with the specimen of interest and does not require any specific calibration sample. In the workflow tip‐sample approach curves are used to extract calibrated complex impedance values and to convert measured S11 reflection signals into sample capacitance and resistance images. The dielectric constant of thin dielectric SiO2 films were determined from the capacitance images and approach curves using appropriate electrical tip‐sample models and the"r value extracted at fD 19:81 GHz is in good agreement with the nominal value of"r 4. The capacitive and resistive material properties of a doped Si semiconductor sample were studied at different doping densities and tip‐sample bias voltages. Following a simple serial model the capacitance‐voltage spectroscopy curves are clearly related to the semiconductor depletion zone while the resistivity is rising with falling dopant density from 20 to 20 k. The proposed procedure of calibrated complex impedance measurements is simple and fast and the accuracy of the results is not affected by varying stray capacitances. It works for nanoscale samples on either fully dielectric or highly conductive substrates at frequencies between 1 and 20 GHz.
125 citations
TL;DR: A previously developed surface polarization model based on the assumption of large electric and ionic charge accumulation at the external contact interface is adopted and able to quantitatively describe exotic features of the perovskite solar cell and provides insight into the operation mechanisms of the device.
Abstract: The analysis of perovskite solar cells by impedance spectroscopy has provided a rich variety of behaviors that demand adequate interpretation. Two main features have been reported: First, different impedance spectral arcs vary in combination; second, inductive loops and negative capacitance characteristics appear as an intrinsic property of the current configuration of perovskite solar cells. Here we adopt a previously developed surface polarization model based on the assumption of large electric and ionic charge accumulation at the external contact interface. Just from the equations of the model, the impedance spectroscopy response is calculated and explains the mentioned general features. The inductance element in the equivalent circuit is the result of the delay of the surface voltage and depends on the kinetic relaxation time. The model is therefore able to quantitatively describe exotic features of the perovskite solar cell and provides insight into the operation mechanisms of the device.
125 citations