Impedance Modulation Research Articles

Acoustic metamaterial for highly efficient low-frequency impedance modulation by extensible design

We propose a novel class of acoustic metamaterial for low-frequency broadband sound absorption with high efficiency. The design principle is physically decoupled into low-frequency mitigation and working frequency widening. The embedded tubes with phase shift are employed to alleviate low-frequency noise, achieving a quasi-perfect absorption (α>0.9) at 240 Hz with the peak value of 0.998. The spider-web-like configuration brings the high-efficiency acoustic impedance modulation via manipulating the coherent coupling effect, and allows for constantly broadening the effective working frequency in lower frequency domain by taming the resonant characteristics and the scale ratio of original and extended units. The theoretical and numerical methods are greatly validated by measured data. We further demonstrate the broadband potentials of the metamaterial, with a continuous quasi-perfect absorption from 301 Hz to 534 Hz (i.e., 1/22 of the operating wavelength) achieved from analytical results. The underlying physics is explained via coherent coupling, acoustic impedance matching, and system damping in detail. All in all, our work provides a viable and effective scheme in overcoming extremely low-frequency broadband noise for lightweight structures.

Design Methods for Dual Polarized Metasurface Antennas: Three Simple Approaches

Metasurface (MTS) antennas are based on the transformation of a cylindrical-wavefront surface wave (SW) into a general wavefront leaky wave (LW). The MTS aperture is constituted by a grounded dielectric slab printed with an electrically dense distribution of subwavelength patches realizing space-variable, homogenized tensor impedance boundary conditions (IBCs). One of the challenges in this type of antenna is related to obtaining dual polarization operations by using the same impedance modulation. In this article, we explore and compare three simple approaches to obtain two beams with orthogonal polarizations by feeding two ports. A first known method is based on exciting both a transverse electric (TE) and a transverse magnetic (TM) SW mode on the same modulated impedance. A second method exploits the concept of impedance modulation sharing, according to which two distinct modulations, designed to radiate different polarizations when properly illuminated by distinct offset feeding points, are superimposed on the same aperture. A third method consists in duplexing an outward (radially diverging) and an inward (converging to the center) SW. Simple analytical formulas are presented for the synthesis of the impedance that allows for the control of the inward/outward waves to ensure balanced radiation performances in terms of aperture efficiency for the two polarizations. A comparison in terms of performances between the latter two approaches is presented.

Wireless Multiferroic Memristor with Coupled Giant Impedance and Artificial Synapse Application

AbstractInternet of things (IoT) becomes part of everyday life across the globe, whose nodes are able to sense, store, and transmit information wirelessly. However, the IoT nodes based on von Neumann architectures realize the memory, computing and communication functions with physical separated devices, which result in severe power consumption and computation latency. In this study, a wireless multiferroic memristor consisting of Metglas/Pb(Zr0.3Ti0.7)O3‐1 mol% Mn/Metglas laminate is proposed, which integrates the storage, processing, and wireless communication of information in a single device at the first time. First, a power efficient impedance modulation mechanism is explored for the multiferroic memristor, which couples electric field modulated giant magnetoimpedance (GMI) of magnetostrictive Metglas with varied impedance of ferroelectric Pb(Zr0.3Ti0.7)O3‐1 mol% Mn due to the gradual polarization switching. Meanwhile a pair of multiferroic memristors are used to transmit and receive stored information wirelessly, which facilitate the application of memristor in the IoT. Furthermore, the experimental study demonstrates that the memristor can mimic the synaptic plasticity, such as long‐term potentiation, depression, and spiking‐timing‐dependent plasticity, and it also reveals the capability of pattern learning with a memristor network. This work paves a way toward the IoT nodes integrating both brain inspired computing and wireless communication functions.

Innovations in ventricular tachycardia ablation.

Catheter ablation of ventricular arrhythmias (VAs) has evolved significantly over the past decade and is currently a well-established therapeutic option. Technological advances and improved understanding of VA mechanisms have led to tremendous innovations in VA ablation. The purpose of this review article is to provide an overview of current innovations in VA ablation. Mapping techniques, such as ultra-high density mapping, isochronal late activation mapping, and ripple mapping, have provided improved arrhythmogenic substrate delineation and potential procedural success while limiting duration of ablation procedure and potential hemodynamic compromise. Besides, more advanced mapping and ablation techniques such as epicardial and intramyocardial ablation approaches have allowed operators to more precisely target arrhythmogenic substrate. Moreover, advances in alternate energy sources, such as electroporation, as well as stereotactic radiation therapy have been proposed to be effective and safe. New catheters, such as the lattice and the saline-enhanced radiofrequency catheters, have been designed to provide deeper and more durable tissue ablation lesions compared to conventional catheters. Contact force optimization and baseline impedance modulation are important tools to optimize VT radiofrequency ablation and improve procedural success. Furthermore, advances in cardiac imaging, specifically cardiac MRI, have great potential in identifying arrhythmogenic substrate and evaluating ablation success. Overall, VA ablation has undergone significant advances over the past years. Innovations in VA mapping techniques, alternate energy source, new catheters, and utilization of cardiac imaging have great potential to improve overall procedural safety, hemodynamic stability, and procedural success.

Radiofrequency impedance spectroscopy of biological tissues under heating by homogeneous laser radiation

We have developed an original method to measure the temperature dependence of the biological tissue electrical properties based on its heating by homogeneous optical radiation.The conventional approach in hyperthermia research involves heating due to a thermal conductivity through the surface of the sample. The novel technique is based on the emission of heat sources in the sample volume caused by the absorption of optical radiation.The method was verified using chicken liver and aloe parenchyma samples, which were uniformly irradiated in a special chamber with an optically scattering inner coating. The electrical impedance of the samples was measured using a 4-electrode technique in the frequency range 100 Hz−1 MHz. In order to approximate and analyze the electrical impedance module, an equivalent electrical circuit based on the Cole-Cole function was used and the dependences of the approximation parameters on time and temperature were obtained. Applying the Arrhenius formulation to the kinetics of low-frequency resistance, we obtained the parameters of the kinetics of degradation of the biological tissues (critical temperature and activation energy ): J mol−1, °C for the aloe parenchyma and J mol−1, for the chicken liver.

A Broadband Doherty-Like Power Amplifier With Large Power Back-Off Range

This paper proposes a novel power amplifier (PA) topology which can realize PA operation with high power back-off range (OBO) and wide bandwidth. Here a short-circuit reactance instead of an additional PA branch is introduced into the isolated port of a coupler to provide the frequency dependency required for broadband load impedance modulation. In addition, the corresponding complex load impedances at each normalized frequency are given to achieve high OBO based on the use of the same transistor in both the carrier PA and peak PA branches. The behaviours of the proposed PA as a function of input power are also derived based on the appropriate complex load impedance. To validate the proposed topology, a PA with 9 dB OBO operating across 1.0-3.0 GHz is designed, fabricated, and tested. Measurements illustrate that the PA can deliver a saturated output power from 44 dBm to 45 dBm over 1.0-3.0 GHz, with a drain efficiency ranging from 62% to 71%. Drain efficiencies are from 41% to 48% at the OBO of 9 dB.

Wideband PPT Class $\Phi _2$ Inverter Using Phase-Switched Impedance Modulation and Reactance Compensation

Class <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\Phi _2}$</tex-math></inline-formula> is a suitable power amplifier (PA) topology for applications that demand low device voltage stress and simple gate driving. The push–pull with T network (PPT) version of this architecture can be advantageous over a conventional single-ended <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\Phi _2}$</tex-math></inline-formula> due to higher power capabilities through interleaving and simple closed-form design equations. The downside with this and many other switch-mode PAs is that they perform efficiently only at a single frequency with the power degrading outside the nominal point of operation. To improve upon this issue, we incorporate a phase-switched impedance modulation variable capacitor and a reactance compensation network so that the PPT <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{\Phi _2}$</tex-math></inline-formula> can function across broadband. We experimentally demonstrate a 300-W PA for a 50- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\Omega }$</tex-math></inline-formula> load impedance using silicon devices. The PA achieves above 90% efficiency over approximately a 30% fractional bandwidth. The PA can also operate across broadband with light loads, where above 80% efficiency is maintained for up to five times higher load resistances. This switch-mode PA is one of the first to demonstrate such performance under load variation and across a wide bandwidth.

Electrical characterization of milk samples by Electrical Impedance Spectroscopy (EIS)

This work presents a study of electrical impedance spectroscopy (EIS) as an alternative to characterize milk, aiming to develop an analysis methodology. The behavior of the electrical impedance module, the real part and the imaginary part (reactance), and the derived quantities such as admittance, phase and diffusion coefficient (D) were also analyzed and will be discussed. Comparisons of the measured spectra with theoretical models of equivalent circuits were carried out in order to understand the electrical behavior of the samples. Understanding this electrical phenomenon will help in the development of future analysis methodologies and applications. The results indicated that milk is a solution with predominantly resistive behavior with resistance of approximately 500 Ohms, capacitance of about of 0.5 MicroFarad (μF) and admittance of the order of MiliSiemens (mS), presenting small storaged charge due to low viscosity. The best-fitting equivalent circuit was a mixed RC model consisting of a series resistor coupled with a resistor in parallel with a capacitor.

Battery-Less Sensing of Body Movements Through Differential Backscattered RFID Signals

RFID tags not only can be used as identification devices, with antenna sensing techniques, they can also be used as low-cost and battery-less sensors. However, RFID antenna sensing relies on the impedance and/or gain modulation of the tag’s antenna, and extracts the sensing information through the RSSI variation of the backscattered signals. The sensing information is prone to the interferences and noises in the reader-tag communication channel, as well as the distance variations if the sensors are in constant motion. In this paper, we propose a sensor structure that is constructed from adjacently placed double tags to address these issues. The EM properties of the antennas of the double tags behave differently (or even oppositely) under the same sensing variation; therefore, the differential backscattered signals of the dual-tag sensor can eliminate the common-mode interferences while preserving the sensing information. We have constructed one curvature sensor and one deformation sensor with embroidered antennas (using conductive yarns) and all-fabric materials, and sewn the sensors on apparels to demonstrate their use in smart clothing applications. The experiments show that even when the human body is in constant motion, the curvature sensor sewn on the knee area can effectively monitor human’s body gesture, while the deformation sensor sewn on the chest area can precisely detect the respiration activities.

Bio-based one-component epoxy resin: Novel high-performance anticorrosive coating from agro-industrial byproduct

In this present work, an epoxy resin produced from an agroindustrial byproduct, cashew nutshell liquid (CNSL), was used for manufacturing a one-component anticorrosive epoxy coating. CNSL-based epoxy resin (e-CNSL) was synthesized using a solvent-free methodology with performic acid generated in situ. The chemical structure of resin was evaluated by FTIR and 1H NMR. The curing parameters of the epoxy-phenol system with 1-methylimidazole (1-MIM) as an accelerator were investigated by differential scanning calorimetry (DSC). The use of only 5% by weight of 1-MIM was efficient to catalyze the reaction, obtaining the lowest cure temperature (150 °C). The coating showed high crosslinking and good thermal-mechanical performance, where the initial decomposition temperature was 200 °C and glass transition temperature was 30 °C. The anti-corrosive performance of e-CNSL/MIM5 exposed to salt spray and 3.5% w/v NaCl solution was monitored by electrochemical impedance spectroscopy, adhesion, and visual evaluation during the exposure period. Humidity test with visual evaluation was also performed. The coating presented high impedance module at 108 Ω.cm2 and high adhesive property, suffering low delamination during the tests. Thus, the one-component bio-based coating developed is promising to be applied for corrosion protection purposes.

Study of Quality Factor (Q) and Phase Angle (θ) obtained per electrical impedance to characterization and detection adulteration in honey.

The quality control of honey is very important for the food industry and for the final consumer. Honey has constantly been the target of adulteration, usually with the aim of illegally increasing profit. However, the analytical methods used in the fraud investigation sometimes are very complex and beyond time-consuming. Electrical measurements appear as a good alternative to the traditional methods of analysis due to its practicality and low costs. In order to show the applicability of some electrical parameters derived from the impedance technique for honey quality control analysis, in the present study, samples were purposefully adulterated with syrup to simulate adulteration conditions. Then, they were submitted to electrical impedance analysis with frequency scanned from 10 Hz to 2 MHz. The impedance module (Z), the phase angle and the quality factor (Q) data were collected and studied. The results showed that there is a linear correlation between the frequencies relative to the peaks of the Q for samples and adulterant concentration with coefficient of determination of ~0.992. The proposal to use the Q as a property to be used in methodologies of analysis is the main contribution from this study, since it is traditionally little mentioned in the literature.

Cylindrical holographic impedance metasurface for OAM vortex wave generation

In this Letter, we present a cylindrical conformal holographic impedance metasurface for orbital angular momentum (OAM) generation. The conformal holographic metasurface is designed by establishing the element library and deducing the formula of holographic tensor impedance modulation. The feasibility of the scheme is verified by simulations and experiments. Simulated and experimental results are in good agreement with theoretical analysis. The results show that OAM vortex wave energy can be generated efficiently by a cylindrical conformal impedance metasurface, which can provide a reference for OAM communication and vortex radars with conformal devices.

Impedance Modulation Control of a Lower-Limb Exoskeleton to Assist Sit-to-Stand Movements

As an important movement of the daily living activities, sit-to-stand (STS) movement is usually a difficult task facing elderly and dependent people. In this article, a novel impedance modulation strategy of a lower-limb exoskeleton is proposed to provide appropriate power and balance assistance during STS movements while preserving the wearer’s control priority. The impedance modulation control strategy ensures adaptation of the mechanical impedance of the human–exoskeleton system toward a desired one requiring less wearer’s effect while reinforcing the wearer’s balance control ability during STS movements. A human joint torque observer is designed to estimate the joint torques developed by the wearer using joint position kinematics instead of electromyography or force sensors; a time-varying desired impedance model is proposed according to the wearer’s lower-limb motion ability. A virtual environmental force is designed for balance reinforcement control. Stability and robustness of the proposed method are theoretically analyzed. Simulations are implemented to illustrate the characteristics and performance of the proposed approach. Experiments with four healthy subjects are carried out to evaluate the effectiveness of the proposed method and show satisfactory results in terms of appropriate power assist and balance reinforcement.

Spatiotemporally modulated reflective acoustic metasurfaces

Nonreciprocal acoustic wave propagation has been the topic of intense study for nearly a decade with the objective of understanding physical requirements to increase control over propagating acoustic waves [Nassar et al., Nat. Rev. Mater. 5(9), 667–685 (2020)]. One approach to achieve non-reciprocity is deterministic spatiotemporal modulation of the material properties of the medium in which waves propagate. Achieving this modulation requires external sources of energy throughout the domain of interest, which presents a significant scientific and technical challenge. Furthermore, the non-reciprocal nature of the acoustic response is not guaranteed for finite domains and finding parameter sets of modulation amplitude, frequency, and wavenumber that lead to significant non-reciprocal behavior is non-trivial [Goldsberry et al., Phys. Rev. B 102(1), 014312 (2020)]. Input impedance modulation of finite acoustic metasurfaces (AMS) presents a more tractable technical challenge. This work considers semi-analytical and numerical modeling of modulated reflective AMS. We present parametric studies of the static input impedance profiles and modulation functions as a linear, time-varying boundary condition of an acoustic half-space. We consider static admittance profiles that are uniform, discontinuous, and continuously varying and how this may influence the effectiveness of spatiotemporal modulation in achieving performance objectives such as acoustic diffusivity.

Toward on-orbit structural health monitoring of inflatablestructures using electromechanical impedance method

Abstract Inflatable structures are promising candidates for a wide range of aerospace vehicles due to their volume/weight savings, high storage rate, low cost, and easy deployment. However, space survivability is a major concern for such structures. Therefore, structural health monitoring (SHM) of inflatable structures has been increasingly studied. Electromechanical impedance (EMI) method is one of the most-popular SHM methods, which can promptly and accurately identify early structural damage. Nevertheless, the necessary of using bulky, expensive and high-power commercial impedance analyzer hampers electromechanical impedance method from being used in-situ and online. In recent years, several miniature impedance measurement devices have been developed for practical applications. However, the aerospace application of such devices is still absence. In this paper, a miniature integrated impedance measurement printed circuit board (PCB) prototype toward on-orbit SHM of inflatable structures is developed. The proposed PCB prototype consists of impedance measurement module, in which the AD5933 chip and the ADG708 chip were adopted to achieve impedance signals. In this case, the PCB prototype can effectively measure the electrical impedance of up to six channels of the piezoelectric transducers at 0.2 ∼ 2V excitation voltage in the frequency range of 10 ∼ 100kHz. Moreover, an inflatable boom was taken as the inspected structure, and a PZT-5H was used as the piezoelectric transducer for experimental validation. The results demonstrate that the proposed PCB prototype works functionally and can accurately quantify the simulated damage on the inflatable boom. In addition, it is found that the miniature integrated impedance measurement PCB prototype developed in this paper has the advantages of low bulk and less weight, which can be further enhanced to satisfy the demands of on-orbit SHM of inflatable structures.

An Optimal Design Method for Improving the Efficiency of Ultrasonic Wireless Power Transmission during Communication.

Due to the excellent directivity, strong penetrability, and no electromagnetic shielding effect, ultrasonic waves have good potential for wireless energy transmission and information transfer inside and outside of sealed metal devices. However, traditional ultrasonic based energy transmission methods usually result in considerable energy consumption because of the impedance mismatch during the impedance modulation of the communication. This paper presents an optimal design method for efficient energy transfer during ultrasonic communication. The channel equivalent circuit model is established by only using the acoustic-electric channel scattering parameters. According to the equivalent circuit model, the channel impedance matches with a weak mismatch state is performed during the communication. In this way, the impedance modulation effect is ensured with a lower decrease in the energy transmission efficiency. Finally, the simultaneous energy transmission and impedance modulation are carried out through the 11 mm thick 304 stainless steel plate. The transmission power is 37.86 W with a transmission efficiency of 45.75%, and the modulation rate is 10 Kbps. Compared with the traditional methods, our proposed energy transmission efficiency is increased by 17.62%. The results verify the proposed method’s effectiveness and the high accuracy of the model. The proposed method has great engineering applications and broad prospects in condition monitoring of metallic environments.

Bioelectrical Impedance Vector and Creatine Phosphokinase Changes Induced by a High-Intensity Training Session in Rink Hockey Players

This study aimed to analyze anthropometric and whole-body/muscle-localized bioelectrical impedance vector analysis (BIVA) adaptations and their relation to creatine kinase (CK) as a biomarker of muscle damage in a group of seven male players in the maximum category of professional rink hockey. There were three checkpoint assessments in relation to a high-intensity training session: pre-session (PRE), post-session (POST), and 24 h-post-session (POST24H). The resistance, reactance, and impedance module were adjusted by height (R/h, Xc/h, and Z/h, respectively). The Wilcoxon signed-rank test was used to compare the data at baseline and follow-up, while Spearman correlation was used to explore the relationship between CK and the rest of the parameters. The results registered a decrease in body mass at POST (p = 0.03) and a reestablishment at POST24H (p = 0.02). Whole-body BIVA registered a significant increase in R/h between PRE–to–POST (p = 0.02) and returned to baseline values at POST24H (p = 0.02), which was expected since this parameter is related to hydration processes. Muscle-localized BIVA in the rectus femoris muscle showed an increase in both Xc/h and phase angle in POST (p = 0.04 and p = 0.03, respectively) and a decrease in Xc/h at POST24H (p = 0.02). CK correlated with R/h in the rectus femoris at all the checkpoints (PRE–to–POST: r = 0.75, p = 0.05; PRE–to–POST24H: r = 0.81, p = 0.03; POST–to–POST24H: r = 0.82, p = 0.02). Our results indicate that BIVA is a sensitive methodology to assess general and muscle-localized hydration induced by a high-intensity training session in rink hockey players. A correlation between BIVA and CK was also reported.

Facile preparation of C/MnO/Co nanocomposite fibers for High-Performance microwave absorption

The C/MnO/Co nanocomposite fibers were prepared via a facile electrospinning and subsequent carbonization process. Co acting as the magnetic nanoparticles and MnO nanoparticles serving as impedance modulator were introduced, effectively inhibiting the agglomeration of carbon fibers during annealing. This optimizes the microstructure and significantly improves the microwave absorption performance of the nanocomposites with diameters of 250–350 nm and rough surface morphologies. The nanocomposite fibers with equal MnO and Co molar contents exhibited the minimum reflection loss of − 71.7 dB at a frequency of 14.1 GHz and an absorber thickness of 2.3 mm, and the effective absorption bandwidth reached at 6.3 GHz at a thickness of 2.6 mm. The high microwave absorption performance can be attributed to the synergistic coactions of conduction loss, magnetic loss, interfacial polarization, and multiple scatterings derived from the rational design of the constituents and microstructure of the nanocomposites.

Electrical Impedance of Surface Modified Porous Titanium Implants with Femtosecond Laser.

The chemical composition and surface topography of titanium implants are essential to improve implant osseointegration. The present work studies a non-invasive alternative of electrical impedance spectroscopy for the characterization of the macroporosity inherent to the manufacturing process and the effect of the surface treatment with femtosecond laser of titanium discs. Osteoblasts cell culture growths on the titanium surfaces of the laser-treated discs were also studied with this method. The measurements obtained showed that the femtosecond laser treatment of the samples and cell culture produced a significant increase (around 50%) in the absolute value of the electrical impedance module, which could be characterized in a wide range of frequencies (being more relevant at 500 MHz). Results have revealed the potential of this measurement technique, in terms of advantages, in comparison to tiresome and expensive techniques, allowing semi-quantitatively relating impedance measurements to porosity content, as well as detecting the effect of surface modification, generated by laser treatment and cell culture.

Time Reversal Communications With Channel State Information Estimated From Impedance Modulation at the Receiver

We determine the channel state information (CSI) of a multiple-input single-output (MISO) Rayleigh channel without prior communications between the transmitting antennas and the receiver. Our approach solely relies on an impedance modulation at the receiver and therefore circumvents the vexing need of a direct feedback between receiver and transmitters. We extract the wavefront to be transmitted in order to achieve optimal focusing on the receiver from a generalized Wigner-Smith operator (WSO). The latter is evaluated based on the scattering matrix of the transmit array measured in the two possible states of the receiver. Based on the CSI extracted via the WSO, any desired precoding technique can be implemented. Here, we show through in-situ time-domain measurements in a reverberation chamber that our approach closely reaches time-reversal performances in terms of focusing efficiency. We expect our approach to open up new perspectives for future wireless communications and wireless power transfer, including applications in the biomedical domain and electronic warfare.