Nonuniform Impedance Research Articles

Rapid Broadband Impedance Acquisition of Lithium-Ion Batteries Based on Measurement Evaluating and Impedance Filtering

Battery impedance contains valuable information concerning state estimation and fault diagnosis, while online impedance measurements attract increasing research interest. The Pseudo Random Sequence (PRS) signal enables a fast and low-complexity impedance measurement for Lithium-ion (Li-ion) batteries yet with the drawback of an inadequate Signal-to-Noise Ratio (SNR) that easily leads to a biased result, while very few studies have existed to process the non-uniformly distributed impedance data with large biases. Motivated by this, this work proposes a novel Measurement Evaluating Procedure (MEP) and a 2-Dimensional Gaussian Filter (2-DGF) for enhancing the performance of the PRS method. The MEP weights the impedance measurement data based on the signal power spectrum and determines the Gaussian Probability Distributions (GPDs) of the impedance data to eliminate interference from the abnormal data. The 2-DGF is further carried out on a semi-logarithmic scale to process the non-uniform impedance measurements, which avoids constantly adjusting the filtering windows. Experimental studies validate the proposed method under the different States of Charges (SOCs) and ambient temperatures. The results present the good accuracy and robustness of the proposed method under different cases.

A theoretical approach for transient shock strengthening in high-energy-density laser compression experiments

In high-energy-density shock compression experiments, the desired state of compression is typically achieved by passing shock waves through a sequence of different materials. In this study, a theoretical approach for transiently strengthening such shocks passing through interfaces of experimentally relevant impedance ratios is examined. A semi-analytical method based on characteristics analysis is used to solve the problem of a shock passing from one material to another through an intermediate region of non-uniform impedance; by appropriately designing this region, a greater shock strength can be achieved in the second material for a finite duration than in the absence of this region. When a shock passes into a material of higher impedance, the shock strengthening increases to a maximum before decreasing to an asymptotic value as the strength of the incident shock is increased. For shocks passing into materials of decreasing impedance, the shock strengthening increases monotonically as the strength of the incident shock is increased when the impedance ratio is above a critical threshold. Incorporating multiple intermediate materials can further increase the strength of the transmitted shock, with an exponential discretization of intermediate material impedances being the most effective distribution for strengthening strong shocks. The results suggest that up to 25% and 9% increases in pressure behind the leading shock can be achieved for materials of increasing and decreasing impedance, respectively. The technique is applied to the design of laser-driven dynamic compression experiments, and the results of the analysis are verified via comparison to simulations performed with the HYADES hydrodynamics code.

Use of non‐uniform RIS and parasitic strips to improve antenna CP performance

The effect of using a non-uniform reactive impedance surface (RIS) on the circular polarisation performance of a planar antenna is investigated. It is shown that a very wide axial ratio (AR) bandwidth can be obtained, especially when the RIS is combined with parasitic strips. This result is only possible, thanks to the fact that the RIS is non-uniform. The technique is demonstrated by designing, building, and measuring a prototype. The simulated impedance bandwidth S 11 ≤ − 10 dB is 43.6% (4.3–6.7 GHz), and the simulated 3 dB AR bandwidth is 37.2% (4.6–6.7 GHz). The gain variation over the 3 dB AR bandwidth is 3–5.9 dBi. The experimental results are in good agreement with the simulations, validating the new concept.

Optimization of Dual Band Two-Section Branch-Line Coupler with Nonuniform Impedances Using Surrogate-Based Method for 5G Applications

Optimization of Dual Band Two-Section Branch-Line Coupler with Nonuniform Impedances Using Surrogate-Based Method for 5G Applications

Sound wave scattering in a flow duct with azimuthally non-uniform liners

Novel acoustic liner designs often incorporate new materials with non-uniform impedance distributions. Therefore, new methods are required for their modelling and analysis. In this paper, a theoretical model is developed to investigate the scattering of sound waves from an axially symmetrical flow duct with a semi-infinite, azimuthally non-uniform acoustic lining on the duct wall. More specifically, the incorporation of Fourier series expansions into the Wiener–Hopf method leads to an analytical model with a matrix kernel, which is further factorised by using the pole-removal method to obtain a closed-form solution. A new mathematical method is developed to solve the residues associated with the pole-removal technique. The proposed model has been verified and validated by comparing with corresponding computational results. In addition to shedding light on the possible physical effect of azimuthally non-uniform liners along with an axial hard–soft interface, the current model enhances the theoretical modelling capability for a complicated set-up of practical importance, and can be used to investigate new liner designs for passive noise control in flow ducts.

Analysis of the Conditions for the Radio Waves Propagation in the Waveguide “Earth-Ionosphere” on the Paths “Novosibirsk-Ulan-Ude” and “Komsomolsk-on-Amur-Ulan-Ude” During Magnetic Storms August 31-September 12, 2017

In order to analyze the radio waves propagation conditions in non-uniform impedance channels, the amplitude and additional phase of the electromagnetic field of the VLF radio navigation system RSDN-20 were measured. The radio paths of latitudinal strike have been studied: path 1 “Novosibirsk - Ulan-Ude”, the length is 1580 km; path 2 “Komsomolsk-on-Amur - Ulan-Ude”, the length is 2080 km. The daily variations of the amplitude and the additional phase of the 11.9 and 14.88 kHz radio signals are considered.

Back Radiation Suppression Through a Semitransparent Ground Plane for a Millimeter-Wave Patch Antenna

Omnidirectional radiation pattern with minimum backward radiation is highly desirable for base station antennas to minimize the multipath effects. Semitransparent ground planes have been used to reduce the backward radiation, but mostly with complicated nonuniform impedance distribution. In this paper, we propose, for the first time, a round semitransparent ground plane of radius $0.8\lambda $ with uniform impedance distribution that can improve the front-to-back ratio of a wide-band patch antenna by 11.6 dB as compared to a similar sized metallic ground plane. The value of uniform impedance is obtained through analytical optimization by using asymptotic expressions in the Kirchhoff approximation of the radiation pattern of a toroidal wave scattered by a round semitransparent ground plane. The semitransparent ground plane has been realized using a low-cost carbon paste on a Kapton film. Experimental results match closely with those of simulations and validate the overall concept.

Effects of Non-Uniform Temperature on In-Situ Current Distribution and Non-Uniform State of Charge Measurements for LiFePO4 and LiNiMnCoO2 Cells

Understanding internal state non-uniformity occurring across the electrodes in large-format Lithium-ion batteries, and among parallel-connected cells, is a critical part of the cell and battery module design process. Two five-cell parallel groups were tested using LiFePO4/C6 (LFP), and LiNiMnCoO2/C6 (NMC) chemistries. Pulse and full-capacity discharges were performed at various States of Charge (SOC), C-rates, average temperatures, and levels of temperature non-uniformity. In pulse testing, the current non-uniformity was lower for the LFP group compared to the NMC group. The hottest cell in the LFP group produced up to 40% more current than average, while this was up to 80% for NMC. Conversely, under charge depleting conditions the NMC group experienced less current non-uniformity, and in certain cases provided a nearly uniform current distribution in the presence of non-uniform temperature. Higher temperature sensitivity in the impedance causes larger current non-uniformity under pulse conditions. However, due to the presence of non-uniform SOC in charge depletion conditions, the Open Circuit Voltage (OCV) versus SOC gradient plays a significant role in controlling the current distribution, where steeper OCV versus SOC minimizes the effect of the non-uniform impedance.

The Research on the Establishment and Simulation of Intelligent Drill String Cables Based on Nonuniform Transmission Line Theory

The cable transmission line has more obvious advantages in long-distance information transmission, and is suitable for the transmission of various MWD signals during drilling. The research on the information transmission pattern of the cable transmission line will be the focus of intelligent drill string. According to the characters of the intelligent drill string, combing with the nonuniform transmission line theory, and considering the effect of temperature variation on the impedance of the smart drill string, the distribution parameters of the cable transmission line has been analyzed. On the basis of the two port network system, the transfer function and the transport matrix of the nonuniform transmission line have been obtained, and the model of nonuniform transmission line impedance of the intelligent drill string cable has been established. In order to verify the feasibility of the established model, the communication channel model has been built utilizing the MATLAB/Simulink software. Through experiment simulation and result analysis, the error rate curves under different parameters have been obtained, the transmission rate and transmission distance of different signals have been explored, and the influence of modulation and demodulation on data transmission quality has been studied, which provides a certain reference for the information transmission pattern of the intelligent drill string.

Current Distribution Measurements in Parallel-Connected Lithium-Ion Cylindrical Cells under Non-Uniform Temperature Conditions

Understanding internal state non-uniformity that occurs across the electrodes in large-format Lithium-ion batteries, and among parallel-connected cells, is a critical part of the cell and battery module design process. Two separate groups of parallel-connected 18650 cells were tested using LiFePO4/C6 (LFP), and LiNiMnCoO2/C6 (NMC) chemistries. Pulse and full-capacity discharges were performed at various States of Charge (SOC), C-rates, average temperatures, and levels of temperature non-uniformity. Current non-uniformity for the pulse testing was always lower for the LFP group compared to the NMC group. The hottest cell in the LFP group produced up to 40% more current than average, while this was up to 80% for NMC. Conversely, under charge depleting conditions the NMC group experienced less current non-uniformity, and in certain cases provided a nearly uniform current distribution in the presence of non-uniform temperature. The results indicate that higher temperature sensitivity in the impedance of a cell will cause larger current non-uniformity under pulse conditions. However, due to the presence of non-uniform SOC for charge depleting, the Open Circuit Voltage (OCV) versus SOC gradient plays a significant role in dictating the current distribution behavior, where steeper OCVs provide a corrective action that minimizes the effect of the non-uniform impedance.

Resonant absorption and amplification of circularly-polarized waves in inhomogeneous chiral media.

It has been found that in the media where the dielectric permittivity ε or the magnetic permeability μ is near zero and in transition metamaterials where ε or μ changes from positive to negative values, there occur a strong absorption or amplification of the electromagnetic wave energy in the presence of an infinitesimally small damping or gain and a strong enhancement of the electromagnetic fields. We attribute these phenomena to the mode conversion of transverse electromagnetic waves into longitudinal plasma oscillations and its inverse process. In this paper, we study analogous phenomena occurring in chiral media theoretically using the invariant imbedding method. In uniform isotropic chiral media, right-circularly-polarized and left-circularly-polarized waves are the eigen-modes of propagation with different effective refractive indices n(+) and n(-), whereas in the chiral media with a nonuniform impedance variation, they are no longer the eigenmodes and are coupled to each other. We find that both in uniform chiral slabs where either n(+) or n(-) is near zero and in chiral transition metamaterials where n(+) or n(-) changes from positive to negative values, a strong absorption or amplification of circularly-polarized waves occurs in the presence of an infinitesimally small damping or gain. We present detailed calculations of the mode conversion coefficient, which measures the fraction of the electromagnetic wave energy absorbed into the medium, for various configurations of ε and μ with an emphasis on the influence of a nonuniform impedance. We propose possible applications of these phenomena to linear and nonlinear optical devices that react selectively to the helicity of the circular polarization.

Acoustic performance of balconies having inhomogeneous ceiling surfaces on a roadside building facade

Balconies provide noise screening effects in residential buildings even with the balcony door opened for natural ventilation. However, the screening effect of a balcony was found to be canceled due to the reflection from the ceiling. This paper describes a balcony whose ceiling is made from materials of inhomogeneous impedance which eliminates this drawback. The nonuniform impedance affects wave behavior by altering the direction of energy flux away from the region of a balcony as it reflects on the ceiling. A proposed realization of the balcony ceiling comprises a closely spaced array of progressively tuned hollow narrow tubes which create a phase gradient. The acoustic performance of a balcony with an inhomogeneous ceiling surface is examined theoretically by a ray-based model. All of the results predicted by the theory fit well with numerical simulations using a two-dimensional finite element method. Balconies with the proposed ceilings have the potential to be widely used in a roadside multi-residential building against the exterior traffic noise.

Sound barriers from materials of inhomogeneous impedance.

Sound barriers are extensively used in environmental noise protection. However, when barriers are placed in parallel on opposite sides of a sound source, their performance deteriorates markedly. This paper describes a barrier made from materials of inhomogeneous impedance which lacks this drawback. The nonuniform impedance affects the way sound undergoes multiple reflections, and in the process traps acoustic energy. A proposed realization of the barrier comprises a closely spaced array of progressively tuned hollow narrow tubes which create a phase gradient. The acoustics of the barrier is theoretically examined and its superiority over conventional barriers is calculated using finite element modeling. Structural parameters of the barrier can be changed to achieve the required sound insertion loss, and the barrier has the potential to be widely used in environmental noise control.

On the method of lumens.

Parent and Allen [(2007). J. Acoust. Soc. Am. 122, 918-931] introduced the "method of lumens" to compute the plane-wave reflectance in a duct terminated with a nonuniform impedance. The method involves splitting the duct into multiple, fictitious subducts (lumens), solving for the reflectance in each subduct, and then combining the results. The method of lumens has considerable intuitive appeal and is easily implemented in the time domain. Previously applied only in a complex acoustical setting where proper evaluation is difficult (i.e., in a model of the ear canal and tympanic membrane), the method is tested here by using it to compute the reflectance from an area constriction in an infinite lossless duct considered in the long-wavelength limit. Neither the original formulation of the method-shown here to violate energy conservation except when the termination impedance is uniform-nor a reformulation consistent with basic physical constraints yields the correct solution to this textbook problem in acoustics. The results are generalized and the nature of the errors illuminated.

On Sound Generation in Cylindrical Flow Ducts with Non-Uniform Wall Impedance

The use of acoustic liners is a common means of noise reduction in jet engine exhausts. The quest for more effective sound absorption mechanisms in cylindrical ducts has led to the consideration of non-uniform liners, with impedance varying circumferentially, axially, or in both directions. The present paper is based on the theory of mode coupling in a non-uniformly lined cylindrical duct and considers the complementary problem of generation of sound or excitation of coupled modes by a source distribution. The sound field due to an arbitrary source distribution is obtained as a superposition of eigenfunctions corresponding to complex eigenvalues for the radial wavenumbers and natural frequencies taking into account that the radial, axial and azimuthal modes are coupled by the non-uniform wall impedance, and including resonant and non-resonant cases. The waveforms are illustrated for point monopole, dipole and quadrupole sources and a continuous monopole distribution. It is shown that a non-uniform liner provides a greater attenuation than a uniform liner with the same average impedance if it is ‘well-matched’ to the sound field, that is, if it has higher impedance at the peaks and lower at the nodes of the standing modes.

Design and research of RF system for 10 MeV compact cyclotron

A 10 MeV compact cyclotron (CYCHU-10) has been developing in Huazhong University of Science and Technology (HUST). The RF system includes a 10 kW RF power generator and a resonance cavity. There is no automatic frequency tuning equipment in the cavity due to space limitations, so the generator must search and track the cavity resonant frequency. AD9850 synthesizer is used to generate RF signal in the experimental prototype, and a fine sinusoidal waveform around 99 MHz is obtained with the method of picking up a special aliased signal from the synthesizer’s output, and the output power level can be set by regulating the resistor connected to the Pin ‘Rset’. The final stage amplifier based on tetrode operates in the grounded cathode configuration, and the schematic of the tetrode circuit is illustrated. The method of searching the resonant frequency is discussed in detail. For the sake of a compact and robust structure, the resonance cavity will adopt non-uniform characteristic impedance coaxial structure, and the magnet surface electroplated with copper will be used as dummy Dees. The precise shapes and dimensions of the cavity are designed and simulation results are carried out in this paper. The distributions of electromagnetic field are illustrated by means of numerical calculation analysis, and the wooden model test is preformed as well.

Acoustic analysis of a rectangular cavity with general impedance boundary conditions

A Fourier series method is proposed for the acoustic analysis of a rectangular cavity with impedance boundary conditions arbitrarily specified on any of the walls. The sound pressure is expressed as the combination of a three-dimensional Fourier cosine series and six supplementary two-dimensional expansions introduced to ensure (accelerate) the uniform and absolute convergence (rate) of the series representation in the cavity including the boundary surfaces. The expansion coefficients are determined using the Rayleigh-Ritz method. Since the pressure field is constructed adequately smooth throughout the entire solution domain, the Rayleigh-Ritz solution is mathematically equivalent to what is obtained from a strong formulation based on directly solving the governing equations and the boundary conditions. To unify the treatments of arbitrary nonuniform impedance boundary conditions, the impedance distribution function on each specified surface is invariantly expressed as a double Fourier series expansion so that all the relevant integrals can be calculated analytically. The modal parameters for the acoustic cavity can be simultaneously obtained from solving a standard matrix eigenvalue problem instead of iteratively solving a nonlinear transcendental equation as in the existing methods. Several numerical examples are presented to demonstrate the effectiveness and reliability of the current method for various impedance boundary conditions, including nonuniform impedance distributions.

Analysis of far-infrared horns, lightpipes, and cavities containing patterned conductive films

A scheme is described for calculating the scattering parameters of patterned conductive films in waveguide. The films can have non-uniform, non-isotropic, and non-local sheet impedances. Once the scattering parameters are known, they can be combined with the scattering parameters of paths, dielectric slabs, and waveguide steps to build up models of complicated components comprising patterned films in profiled lightpipes and cavities. It is then straightforward to calculate the Stokes fields of the total reception pattern, the natural optical modes to which the component is sensitive, the Stokes fields of the individual natural modes, and the spatial state of coherence. The method is demonstrated by modeling an absorbing pixel in a length of shorted multimode waveguide. The natural optical modes change from being those of the waveguide to those of a free-space pixel as the size of the absorber is reduced.

Interconnect-Based Design Methodologies for Three-Dimensional Integrated Circuits

Design techniques for three-dimensional (3-D) ICs considerably lag the significant strides achieved in 3-D manufacturing technologies. Advanced design methodologies for two-dimensional circuits are not sufficient to manage the added complexity caused by the third dimension. Consequently, design methodologies that efficiently handle the added complexity and inherent heterogeneity of 3-D circuits are necessary. These 3-D design methodologies should support robust and reliable 3-D circuits while considering different forms of vertical integration, such as system-in-package and 3-D ICs with fine grain vertical interconnections. Global signaling issues, such as clock and power distribution networks, are further exacerbated in vertical integration due to the limited number of package pins, the distance of these pins from other planes within the 3-D system, and the impedance characteristics of the through silicon vias (TSVs). In addition to these dedicated networks, global signaling techniques that incorporate the diverse traits of complex 3-D systems are required. One possible approach, potentially significantly reducing the complexity of interconnect issues in 3-D circuits, is 3-D networks-on-chip (NoC). Design methodologies that exploit the diversity of 3-D structures to further enhance the performance of multiplane integrated systems are necessary. The longest interconnects within a 3-D circuit are those interconnects comprising several TSVs and traversing multiple physical planes. Consequently, minimizing the delay of the interplane nets is of great importance. By considering the nonuniform impedance characteristics of the interplane interconnects while placing the TSVs, the delay of these nets is decreased. In addition, the difference in electrical behavior between the horizontal and vertical interconnects suggests that asymmetric structures can be useful candidates for distributing the clock signal within a 3-D circuit. A 3-D test circuit fabricated with a 180 nm silicon-on-insulator (SOI) technology, manufactured by MIT Lincoln Laboratories, exploring several clock distribution topologies is described. Correct operation at 1 GHz has been demonstrated. Several 3-D NoC topologies incorporating dissimilar 3-D interconnect structures are reviewed as a promising solution for communication limited systems-on-chip (SoC). Appropriate performance models are described to evaluate these topologies. Several forms of vertical integration, such as system-in-package and different candidate technologies for 3-D circuits, such as SOI, are considered. The techniques described in this paper address fundamental interconnect structures in the 3-D design process. Several interesting research problems in the design of 3-D circuits are also discussed.

MINIATURIZED MICROSTRIP DUAL-BAND BANDSTOP FILTERS USING TRI-SECTION STEPPED-IMPEDANCE RESONATORS

A novel circuit structure of dual-band bandstop fllters is proposed in this paper. This structure comprises two shunt-connected tri-section stepped impedance resonators with a transmission line in between. Theoretical analysis and design procedures are described. The derived synthesis equations have two degrees of freedom which provide more design ∞exibility in fllter synthesis. Notably, three advantages of the proposed fllter structure lie in the fact of its increased nonuniform impedances, resulting in a compact size, wide range of realizable frequency ratio, and more realizable impedances. Three experimental dual-band bandstop fllters with various frequency ratios were fabricated to demonstrate the feasibility of the new fllter structure.