Mode Impedance Research Articles

Design and Modeling of Dual-Band Dual-Mode Coupled Shorted Patch Antennas

This article presents the coupled shorted patch antennas (CSPAs), which exhibit dual-band operation of both broadside and conical radiation patterns and successfully overcome the major disadvantage of the large H-plane cross-polarization radiation of conventional shorted patch antennas (SPAs). The basic concept behind this breakthrough innovation is to create and explore the coupled TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> modes. It will be shown that the CSPAs provide the horizontally polarized broadside radiation under the odd coupled TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> mode for the low band and vertically polarized conical radiation patterns under the even coupled TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> mode for the high band, respectively. The CSPAs have smaller resonant sizes when compared with those of the conventional SPAs for broadside radiation. The sum of the two resonant frequencies for the CSPAs is twice of that for the corresponding conventional SPAs based on a single microstrip. The ratio of two resonant frequencies depends on the odd and even mode impedances of the coupled microstrips. The calculated results are validated with the simulated and measured ones.

The Impact of COVID-19 Pandemic and Lockdown Restrictions on Cardiac Implantable Device Recipients with Remote Monitoring.

From 2020, many countries have adopted several restrictions to limit the COVID-19 pandemic. The forced containment impacted on healthcare organizations and the everyday life of patients with heart disease. We prospectively analyzed data recorded from implantable defibrillators and/or cardiac resynchronization devices of Italian patients during the lockdown (LDP), post-lockdown period (PLDP) and a control period (CP) of the previous year. We analyzed device data of the period 9 March 2019–31 May 2020 of remotely monitored patients from 34 Italian centers. Patients were also categorized according to areas with high/low infection prevalence. Among 696 patients, we observed a significant drop in median activity in LDP as compared to CP that significantly increased in the PLDP, but well below CP (all p < 0.0001). The median day heart rate and heart rate variability showed a similar trend. This behavior was associated during LDP with a significant increase in the burden of atrial arrhythmias (p = 0.0150 versus CP) and of ventricular arrhythmias [6.6 vs. 1.5 per 100 patient-weeks in CP; p = 0.0026]; the latter decreased in PLDP [0.3 per 100 patient-weeks; p = 0.0035 vs. LDP]. No modifications were recorded in thoracic fluid levels. The high/low prevalence of COVID-19 infection had no significant impact. We found an increase in the arrhythmic burden in LDP coupled with a decrease in physical activity and heart rate variability, without significant modifications of transthoracic impedance, independent from COVID-19 infection prevalence. These findings suggest a negative impact of the COVID-19 pandemic, probably related to lockdown restrictions.

Analysis of sound radiation from a vibrating elastically supported annular plate using compatibility layer and radial polynomials

This study investigates the problem of sound radiation from a thin vibrating annular plate. The plate is supported elastically at its circumference and embedded into the bottom of a circular cavity in a rigid plane. The selected model provides results covering the occurrence of sound radiation from the thin annular plates with any arbitrary boundary configurations. The cavity and the half-space are filled with air, and the air in the cavity plays the role of the compatibility layer. Therefore, the vibrations of the plate are coupled with that of air. Application of the compatibility layer allows the decomposition of the coupled problem of sound radiation to two problems: one for the vibration of the plate coupled with the cavity and the other for the sound radiation from the cavity to the half-space. Consequently, the plate is not coupled to the half-space directly. Therefore, the modal impedance coefficient of the plate is not required to solve the problem. The coefficients of the cavity are sufficient for the calculations, and they can be calculated significantly faster than in the case of performing a numerical integration while simultaneously satisfying the assumed accuracy by using radial polynomials. This also makes it possible to simplify numerical calculations. Finally, the total acoustic power, the acoustic pressure, and the vibration velocity have been obtained using the proposed approach and analyzed numerically. In the specific case when the cavity depth is reduced to zero, the nondimensionalized added virtual mass incremental as well as the modal impedance coefficients of the plate are calculated. Using the obtained results, the resonant frequencies can be accurately determined within a broad frequency band. The described method can be used for calculating the sound radiation for any arbitrary boundary configuration of the thin annular plates. In addition, the proposed approximation reduces the time required for the numerical calculations by roughly 2000 times compared to the time required for the numerical integration.

Examination of Film Thickness Dependence on Acoustic Impedance of Gold and Chromium Thin Films by Scanning Acoustic Microscopy

Thickness induced changes in acoustic impedance of gold (Au) and chromium (Cr) thin films are studied with scanning acoustic microscopy (SAM). Thin films are produced by thermal evaporation technique on BK7 glass substrates with varying thicknesses between 40 nm to 200 nm. In acoustic impedance (AI) mode, the microscope generates two-dimensional acoustic impedance maps of the thin films and micrometer resolution helps determining the surface defects on these films. On the other hand, acoustic impedance value is found to increase as thickness increases for both Au and Cr thin films indicating increased elasticity, therefore, hardness. The mean and standard deviation values of acoustic impedance of Cr thin films were found as 1.901 ± 0.050 MRayl for 40 nm, 1.905 ± 0.045 MRayl for 80 nm, 1.943 ± 0.049 MRayl for 120 nm, 1.964 ± 0.049 MRayl for 160 nm and 1.987 ± 0.052 MRayl for 200 nm. The mean and standard deviation values of acoustic impedance of Au thin films were found as 1.725 ± 0.026 MRayl for 80 nm and 1.954 ± 0.047 MRayl for 200 nm. This success achieved by SAM, demonstrates its potential in monitoring thin film surfaces even with very small thicknesses.

Design Control and Performance of a Cable-Driving Module With External Encoder and Force Sensor for Cable-Driven Parallel Robots

Abstract Cable-driven parallel robots (CDPRs) have the characteristic of easy deployment, which endows CDPRs with flexible workspace, freely configurable degrees-of-freedom (DOFs), and various configurations, greatly expanding their range of applications. Modular design provides excellent convenience and feasibility for deployment, which is a crucial issue of CDPR design. A highly integrated cable-driving module is designed in this paper, which includes the winding bobbin, servo motor, force sensor, external encoder, electromagnetic brake, as well as other devices. Experiments show that the maximum cable length control error is less than 0.16%, and the maximum cable tension control error is less than 8% in the back-and-forward rotation test. Furthermore, a CDPR with eight cables and six DOFs is constructed rapidly using the proposed module, whose dimension is 850 × 850 × 650 mm3. Results show that the robot’s trajectory errors are all less than 4.5 mm, and the root-mean-square-error (RMSE) is 2.1 mm. Besides, the compliance control experiments show that the robot’s tracking error in an impedance control mode is less than 2 mm, and the RMSE is 0.95 mm. Moreover, the dragging force in a teaching mode is less than 2.5 N. The proposed integrated cable-driving module could be helpful for the modular design and deployment of CDPRs.

Fault tolerant control based on backstepping nonsingular terminal integral sliding mode and impedance control for a lower limb exoskeleton

In this paper, an active fault-tolerant control scheme is proposed for a lower limb exoskeleton, based on hybrid backstepping nonsingular fast terminal integral type sliding mode control and impedance control. To increase the robustness of the sliding mode controller and to eliminate the chattering, a nonsingular fast terminal integral type sliding surface is used, which ensures finite time convergence and high tracking accuracy. The backstepping term of this controller guarantees global stability based on Lyapunov stability criterion, and the impedance control reduces the interaction forces between the user and the robot. This controller employs a third order super twisting sliding mode observer for detecting, isolating ad estimating sensor and actuator faults. Motion stability based on zero moment point criterion is achieved by trajectory planning of waist joint. Furthermore, the highest level of stability, minimum error in tracking the desired joint trajectories, minimum interaction force between the user and the robot, and maximum system capability to handle the effect of faults are realized by optimizing the parameters of the desired trajectories, the controller and the observer, using harmony search algorithm. Simulation results for the proposed controller are compared with the results obtained from adaptive nonsingular fast terminal integral type sliding mode control, as well as conventional sliding mode control, which confirm the outperformance of the proposed control scheme.

An ultra‐wideband bandstop filter with circularly etched stub resonator

AbstractIn this letter, an ultra‐wide band bandstop filter (BSF) with three transmission zeros and one reflection zero is presented. The role of the circular etched shaped stub as a notch pass response is investigated. Further, a compact size of 13 mm × 24.30 mm (0.219λg× 0.410λg) is achieved by employing an interdigital capacitor to increase coupling between the lines. Furthermore, the transmission line model of the filter is proposed, and consequently even and odd mode impedance is calculated analytically. The proposed filter offers an ultra‐wide bandwidth of 6.1 GHz (3.7 GHz‐9.8 GHz) with a rejection depth of 20 dB over the entire rejection band. Moreover, the upper skirt factor of 47.2 dB per GHz is achieved. A prototype of the proposed BSF is fabricated and measured. Simulated and measured results are in good agreement which validates the proposed design.

Dual-Arm Coordinated Control Strategy Based on Modified Sliding Mode Impedance Controller.

To meet the high-accuracy position/force control requirements of dual-arm robots for handling a target object, a control algorithm for dual-arm robots based on the modified sliding mode impedance controller MSMIC(tanh) is proposed. First, the combinative kinematics equation of the dual-arm robots and the unified dynamics model combining the manipulated object is established. Second, according to the impedance control motion model for the object, the desired joint angular accelerations of the manipulators are obtained, and the sliding mode controller based on the hyperbolic tangent function as the switch function is introduced to design the coordinated control strategy for dual-arm robots. The stability and convergence of the designed controller are proved according to the Lyapunov function theory. Finally, the operation tasks of the coordinated transport the target object for dual-arm robots are carried out in the simulated experiment environment. Simulation results show that the proposed control scheme can stably output the required internal force and achieve a high-precision trajectory tracking effect while reducing the periodic torque and joint chattering amplitude generated in the conventional sliding mode control algorithm.

Compact wideband bandpass filter based on coupled line stub with high selectivity

Two bandpass filters with the cross shaped resonator and parallel coupled lines are proposed. It has two fixed transmission zeros (TZ) which are located at 0 and 2pi. With the assistance of two types of parallel coupled line, two bandpass filters have other two TZs. Two TZs only depend on the odd and even mode impedance of open parallel coupled line stubs or short parallel coupled line stubs. By adjusting the odd- and even-mode impedance values, two TZs can be adjusted and the frequency selectivity of the bandpass filters are improved. Two bandpass filters are fabricated and measured. The experimental results are basically consistent with the simulation results, which verifies the filter design method.

Study on a multifactor coupling accelerated test method for anticorrosive coatings in marine atmospheric environments

According to the physical and chemical multifield coupling effects on anticorrosive coatings under marine atmospheric environments, the correlations between various environmental factors were analyzed, and a multifactor coupling accelerated test spectrum of the marine atmospheric environment was designed. Moreover, an ultraviolet (UV)/salt spray coupling acceleration test chamber was also designed and prepared, and a multifactor coupling accelerated test method for marine atmospheric environments was established. The mechanism of the changes in light loss rate, adhesion, low-frequency impedance mode value, and aging composite index of a typical engineering coating system (acrylic polyurethane/epoxy/carbon steel system) under multifactor coupling acceleration environments were tracked, analyzed, and compared with the aging curves of a coating subjected to UV/salt spray cycle accelerated and marine atmospheric outdoor exposure tests in Wanning, China. The Corrcoef function in MATLAB was used to calculate the correlation among the aging curves of the three environmental coatings. Results indicated that the multifactor coupling accelerated test had better correlation with outdoor exposure test than the UV/salt spray cycle accelerated test.

European early experience with a novel 3D mapping system

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Catheter navigation and 3-dimensional (3D) cardiac mapping are critical for successful electrophysiological ablation procedures. A novel 3D mapping system received CE Mark in July 2020. The system offers two imaging modalities: magnetic-based (VoXel) and impedance-based (NavX). Real-time display of 3D location and catheter movements is achieved via a magnetic field frame and magnetic sensors with supplemental impedance data when operating in VoXel mode or primarily via an impedance field generated from surface electrodes in NavX mode. To address limitations in data collection commonly experienced during 3D mapping, a new respiratory compensation algorithm, patient movement detection module, and metal compensation algorithm have been developed to enable consistent data collection throughout the full respiratory cycle even in challenging cases and lab environments. Purpose To examine the clinical utility and procedural characteristics associated with the use of this novel 3D mapping system among participating centers. Methods Procedural data was collected in cases utilizing the newly cleared mapping system during the initial evaluation phase in Europe. Procedural characteristics recorded included indication for mapping and ablation, rhythm mapped, chambers mapped, and procedure time. Results Procedural data was collected from over 250 cases across 12 European centers. A total of 12 indications for mapping and ablation were represented including de novo and redo atrial fibrillation (paroxysmal, persistent, long-standing persistent), ventricular tachycardia (ischemic, non-ischemic) or premature ventricular contraction, and supraventricular arrhythmias (typical and atypical atrial flutter, atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia). Over 70% of the cases were performed in VoXel mode. Impedance mode was mostly used in SVT cases or when the case was intended to be completed with minimal fluoroscopy. The most commonly mapped rhythms were sinus rhythm during voltage mapping and atrial tachycardia. The majority of cases (over 65%) were completed under conscious sedation; general anesthesia was used in 20% of the cases (15% not reported). The respiratory compensation algorithm was utilized in over 90% of the cases. For cases in which pre-procedural computed tomography or magnetic resonance imaging were available, operators indicated that the model shape was accurate when compared to pre-procedural imaging in 96% of the cases performed in VoXel mode. Conclusions Initial European experience with this novel 3D mapping system included a wide variety of arrhythmias in the atria and ventricles. This new mapping system offered operators the flexibility to tailor to specific procedure needs with two imaging modalities which were both widely utilized.

Design of a Charge Pump Circuit and System with Input Impedance Modulation for a Flexible-Type Thermoelectric Generator with High-Output Impedance

This paper describes a charge pump system for a flexible thermoelectric generator (TEG). Even though the TEG has high-output impedance, the system controls the input voltage to keep it higher than the minimum operating voltage by modulating the input impedance of the charge pump using two-phase operation with low- and high-input impedance modes. The average input impedance can be matched with the output impedance of the TEG. How the system can be designed is also described in detail. A design demonstration was performed for the TEG with 400 Ω. The fabricated system was also measured with a flexible-type TEG based on carbon nanotubes. Even with an output impedance of 1.4 kΩ, the system converted thermal energy into electric power of 30 μW at 2.5 V to the following sensor ICs.

Comments on “An Analog Bootstrapped Biosignal Read-Out Circuit With Common-Mode Impedance Two-Electrode Compensation”

This paper comments on a recently published article by Parente et al.

Compact low‐loss millimeter‐wave shielded asymmetrical coplanar stripline to unilateral and antipodal finline transitions

Compact and low-loss U-band shielded asymmetrical coplanar stripline (SACPS) to unilateral and antipodal finline transitions are proposed in this article for millimeter-wave circuits and systems applications. The principles of mode conversion and impedance matching are applied to the proposed transitions. In the SACPS to unilateral finline transition, the SACPS is firstly transformed into the asymmetrical unilateral finline to convert the quasi-TEM mode to the quasi-TE10 mode and then a tapered unilateral finline section is applied to realize impedance matching. For the U-band back-to-back SACPS to unilateral finline transition, the measured return loss is larger than 15 dB and the insertion loss is less than 1.5 dB with a minimum of 0.5 dB. In the SACPS to antipodal finline transition, the SACPS is firstly transformed into the defected ground microstrip (DGM) without changing the characteristic impedance. Then, the DGM is transformed into the asymmetrical antipodal finline to make mode conversion. At last, a tapered antipodal finline section is used for impedance matching. For the U-band back-to-back SACPS to antipodal finline transition, the measured return loss is larger than 12 dB and the insertion loss is less than 1.5 dB with a minimum of 0.3 dB.

Study of a 560-mm-long stripline kicker for HIT 10 MeV electron accelerator

A stripline kicker is required for Harbin Institute of Technology (HIT) 10 MeV electron accelerator to scan electrons horizontally in two directions, and the maximum deflecting angle is 65 mrad. In this study, a 560-mm-long stripline kicker was designed to achieve good field uniformity and odd mode impedance matching. In order to reduce power reflections and meet field uniformity requirement, we optimized the cross section of the kicker main body. Design and optimization of the stripline kicker were finished by CST. The field uniformity is 2% in the 60 mm (x) × 80 mm (y) region, as required. Considering impedance matching and manufacturing, the transmission odd mode impedance was finally chosen to 45 Ω, which indicated a reflecting loss of less than −50 dB below 1 MHz. The maximum field is less than 7 MV/m with a maximum pulse voltage of ±22 kV between the two electrodes when the electrons pass through the kicker. The physical design of the stripline kicker has been finished, and the simulation results satisfied the requirements.

Extension of the single-nonlinear-mode theory by linear attachments and application to exciter-structure interaction

Under certain conditions, the dynamics of a nonlinear mechanical system can be represented by a single nonlinear modal oscillator. This holds, in particular, under external excitation near primary resonance or under self-excitation by negative damping of the respective mode. The properties of the modal oscillator can be determined by computational or experimental nonlinear modal analysis. The simplification to a single-nonlinear-mode model facilitates qualitative and global analysis, and substantially reduces the computational effort required for probabilistic methods and design optimization. Important limitations of this theory are that only purely mechanical systems can be analyzed and that the respective nonlinear mode has to be recomputed when the system’s structural properties are varied. With the theoretical extension proposed in this work, it becomes feasible to attach linear subsystems to the primary mechanical system, and to approximate the dynamics of this coupled system using only the nonlinear mode of the primary mechanical system. The attachments must be described by linear ordinary or differential-algebraic equations with time-invariant coefficient matrices. The attachments do not need to be of purely mechanical nature, but may contain, for instance, electric, magnetic, acoustic, thermal or aerodynamic models. This considerably extends the range of utility of nonlinear modes to applications as diverse as model updating or vibration energy harvesting. As long as the attachments do not significantly deteriorate the host system’s modal deflection shape, it is shown that their effect can be reduced to a complex-valued modal impedance and an imposed modal forcing term. In the present work, the proposed approach is computationally assessed for the analysis of exciter-structure interaction. More specifically, the force drop typically encountered in frequency response testing is revisited. A cantilevered beam with cubic spring and an attached electro-dynamical shaker serves as benchmark. The proposed approach shows excellent accuracy. Mainly the already known limitations of single-nonlinear-mode theory reappear. In particular, higher harmonics should not be too pronounced. In the transient case, the time scales of vibration and amplitude-phase modulation should be well separated, and the attachment dynamics should be in quasi-steady state.

Studies of Radial and Thickness Acoustic Resonance Modes of a Piezoceramic with Mixed Polarization Geometry

In this study, the Pb(Zr0.65Ti0.35)O3 (PZT) structure was produced by the solid state reaction method, and a new polarization geometry was used to obtain the radial and thickness modes in cylindrical samples with more efficiency. The polarization procedure was investigated by varying the temperature from 30°C to 80°C. The experimental excitation of radial and thickness modes was observed, and a comparative study was performed with numerical simulations. The comparative analysis of the acoustic response of the cylindrical PZT samples under theoretical and experimental conditions was validated by COMSOL Multiphysics® software. The new polarization geometry technique was used to generate radial thickness and acoustic mixed modes with more efficiency. The results show that the resonance frequency and antiresonance, as well as the impedance mode and phase angle are well adjusted, showing the validation of the technique presented between the theoretical and experimental measurements.

A 8–12 GHz, 44.3 dBm RF output class FF−1 DPA using quad-mode coupled technique for new configurable front-end 5G transmitters

This paper presents a high-efficiency Class $${\mathrm{FF}}^{-1}$$ DPA using the quad-mode coupled technique for new configurable front-end 5G transmitters. The proposed DPA consists of carrier PA, main PA, input–output matching network and hybrid power network (HPN). The HPN includes a quad-mode coupled technique which is four-section U-shaped transmission line. The HPN is used for even–odd mode impedance analysis to ensures the high-selectivity of output power and achieve a wideband response in the presence of harmonic control conditions. The optimum harmonic impedance is analyzed for the desired band to achieve high output power and efficiency. The DPA circuit is fabricated by using 0.25 µm GaN HEMT on silicon nitride monolithic microwave integrated circuit die process. At maximum output power level of 44.3 dBm, the delivered power-added efficiency (PAE) of 64.3–67.3% and drain efficiency (DE) of 71.7–73.7% at even–odd mode operation are achieved with a gain of 13.0–14.3 dB. For the output power level of 39.045 dBm corresponding to 9 dB output back-off (OBO), the drain efficiency lies between 55–62% with 73% fractional bandwidth. All the demonstrated transmission parameters are working in the band of 8–12 GHz. The size of the chip is 2.8 × 1.9 mm2 and it occupies less die area as compared to the existing DPAs.

An algorithm for fitting passive equivalent circuits for lumped parameter frequency dependent transmission line models

Accurately fitting rational functions to the frequency response of modal impedances is crucial for including frequency dependency in lumped parameter models of transmission lines. Vector fitting is widely used for fitting rational functions to the frequency response of modal impedances and then an R-L equivalent circuit is obtained from the rational functions. A single-step method based on the properties of Foster equivalent circuit is proposed to directly fit an R-L equivalent circuit to the frequency response of modal impedances. The positive peaks, negative peaks and the positive zero crossings of the slope change plot of the frequency response are found to provide a good approximation of zeros, poles and the flat region locations of the frequency response. An enhanced fitting algorithm is proposed based on these observations. A close enough fitting is achieved using the proposed method with less number of passive elements. Using the proposed model in EMTP-RV, 400, 765, 1200 kV transmission lines and a 11-bus 500 kV network are simulated for switching transients. The results are compared with the constant parameter cascaded (Formula presented.) -model and the universal line model in EMTP-RV. The switching transient results of the proposed model are found to be comparable to the Marti's model in EMTP-RV. © 2021 The Authors. IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology

Impedance control based on optimal adaptive high order super twisting sliding mode for a 7-DOF lower limb exoskeleton

In this paper, a novel hybrid optimal Adaptive High-Order Super Twisting Sliding Mode (AHOSTWSM) impedance control is proposed for a lower limb exoskeleton robot with 7 active joints, which takes the interaction forces between the robot and the user into account. First, the dynamic model of the robot is extracted using Lagrange approach. Then, an adaptive super twisting sliding mode controller is designed based on Lyapanov theory. Moreover, the interaction forces are obtained in every time-step and applied to the robot as a compensating torque to guard against disturbances. The desired trajectory of the upper limb joint has been extracted so that the stability of the robot is achieved based on Zero Moment Point (ZMP) criterion at any moment. Moreover, to achieve optimal performance (maximum stability, minimum tracking error, reduced interacting forces, and optimal energy consumption), parameters of the proposed controller, the upper limb desired trajectory, and the impedance system are optimized using Harmony Search Algorithm (HSA). Finally, in order to demonstrate the effectiveness of the proposed controller, optimal sliding mode controller (SMC) is designed and performance of the AHOSTWSM is compared with SMC. The simulation results reveal the superiority of the controller in comparison with SMC.