Improved Isolation Performance Research Articles

Is there a right answer? A cross-laboratory study of concrete slabs

Commissioning a new acoustic test lab is a non-standardized process and validating test procedures and conditions is complicated by a lack of test samples with established performance. To aid in validating the results at the Maxxon Acoustics Lab, two concrete slabs were fabricated and tested in a Gage Repeatability and Reproducibility-style test design at Intertek Labs. After shipment from York, PA to Hamel, MN, mounting and edge conditions were established (as previously presented) at the Maxxon Labs, and the Gage R&R-style testing was replicated at the Maxxon Lab. The results indicate sources of variability between labs that can be attributed to the standard test methods, physical differences in reverberation rooms and test chamber design, and sample mounting conditions. In addition to validation of a single lab, the results have lessons for the interpretation of lab test results to improve isolation performance comparison across products and assemblies to inform architectural acoustic design.

CIQBCP-MIMO-DRA: CSRR inspired quad band circularly polarized MIMO-DRA for W-LAN, Wi-Max, Wi-Fi (6E) and X-band applications

Abstract This paper emphasizes on amalgamation of MIMO antenna with DRA structures; explicitly useful to wireless applications. The feeding mechanism is accomplished by the symmetrically positioned tapered Y-shape lines. The design also encompasses a CSRR geometry along with two metallic reflectors. The incorporation of CSRR introduces novel investigation into traditional designs, resulting in improved isolation performance of the MIMO design. In order to demonstrate the effectiveness of the mentioned antenna, we performed a simulation using ANSYS-HFSS. Subsequently, a physical model was developed and tested. It confirms four different resonating points as 2.56, 4.08, 5.76, and 9.12 GHz with isolations of 36, 47.3, 33.9, and 33 dB respectively. In addition, a few other important parameters relevant to MIMO have been considered and presented in the form of ECC, MEG, DG, CCL, and TARC which claim the dominancy of the stated antenna under the MIMO diversity scenario. In summary, we have presented a model that demonstrates a strong correlation between the simulated and measured outcomes.

Active Negative Stiffness Regulation and Precision Micro-Vibration Isolation Technology Based on Composite Feedback of Acceleration and Velocity

An active negative stiffness regulation and precision micro-vibration isolation technology (ANSVIT) based on composite feedback of acceleration and velocity is proposed to realize the low-frequency isolation of air floating isolators with heavy loads. Adjustable negative stiffness generated by acceleration feedback realizes low-frequency isolation, and absolute velocity feedback is combined to reduce the peak vibration transmissibility and improve isolation performance. The effects of feedback coefficients in the frequency domain are analyzed based on the dynamics model. And the relationship of feedback coefficients that achieves low natural frequency and lower peak vibration transmissibility than passive vibration isolation is derived to guide design. Furthermore, the effects of ANSVIT on vibrations in the low-frequency region, resonance region, and isolation region are investigated numerically in the time domain. Finally, an experimental setup is built, and experiments are conducted. Experimental results show that the introduction of ANSVIT attenuates the natural frequency by 61.54% and achieves lower peak vibration transmissibility and higher vibration level than passive vibration isolation. The promise of the proposed ANSVIT for improving the isolation performance is verified.

Research on the effects of raft on vibration isolation

The floating raft vibration isolation system includes upper and lower isolators and middle raft. As one of the most important parts that affect the performance of vibration isolation, the raft is usually assumed to be an undamped or viscous damping structure in the analysis, which is different from the actual situation. To study the effects of raft with hysteresis damping characteristics, a three-freedom complex stiffness mechanical model was built, and an approach for calculating the raft's force transmission rate was derived from impedance methods. Based on the mechanical model and a large-sized floating raft, we analysed the effects of raft mass, stiffness and damping on vibration isolation through numerical calculation. Results show that increasing raft mass improved vibration isolation over most frequency ranges; increase in raft stiffness contributed to improved isolation performance over frequency ranges near its low-order natural frequencies, while reduced the performance over higher frequency ranges; and greater raft damping led to enhanced vibration isolation at its natural frequencies and higher frequency ranges.

Structural optimization and experiment of a semi-active hourglass-type electromagnetic isolator with negative resistance shunt circuit

The present work proposed a semi-active electromagnetic isolator with negative resistance shunt circuit to improve isolation performance on micro-vibration. By an innovative combination of an hourglass-type displacement amplifier and electromagnetic mechanism with negative resistance shunt circuit, the proposed isolator can not only solve the difficulty for electromagnetic isolators to isolation micro-amplitude vibration but also achieve a significant electromechanical coupling effect to obtain excellent vibration isolation performance by a self-sensing method. First, the design of the isolator and motion relationship are presented. Then, the electromechanical coupling dynamic model of the isolator is established. Moreover, the angle of the hourglass-type displacement amplifier is optimized, and the influence of the negative resistance on the additional damping ratio and system stability is explored. Finally, the isolator was manufactured and several experiments were carried on. The experiment results demonstrated that the isolator has an excellent isolation performance. And meanwhile, the comparison between experiment and simulation also indicated the correctness of the model.

Static and dynamic properties of eggshell filled natural rubber composites for potential application in automotive vibration isolation and damping

The development of high performance, sustainable material alternatives is an increasingly important goal to reduce the automotive industry's carbon footprint. We have investigated the effect of eggshells, a widely available renewable material, as partial and complete replacements of petroleum-derived carbon black in natural rubber composites for automotive anti-vibration applications. At a fixed equal total filler weight, a comparable level of reinforcement was achieved at low replacements (up to 20%) of carbon black N330 with eggshell in the reference formulation. Furthermore, pairs of composites formulated for similar hardness had similar mechanical properties, improved isolation performance with very similar damping and static stiffness (Ks), despite the difference in carbon black/eggshell ratio among them. Particularly, composites made with 20 phr (parts per hundred rubber) of eggshell and 40 phr of carbon black (C40E20) had remarkable mechanical performance, better isolation at high frequencies while maintaining similar damping at low frequency and Ks compared to carbon black alone. Addition of eggshell also improved the processing of the compound and allowed for more filler to be added to the formulation, resulting in an increase in the renewable fraction in the material and a reduction in the energy required for processing. Given the large amount of filler used in automotive rubber components, even a small fraction of carbon black replacement would represent a very large environmental gain for the industry.

All-Port-Reflectionless Narrowband Filtering Power Divider Topology With Generic Equations

In this paper, a new filtering power divider topology is presented. The divider is distinguished from traditional power dividers as it is capable of having a predefined transmission response, an improved isolation performance between the two output ports over a wide frequency range, and reflectionless responses at all three ports. Since the proposed divider topology is based on complete closed-form design equations derived through a rigorous mathematical analysis, it make it possible to design reflectionless filtering power dividers with any prespecified requirements without using time-consuming parametric optimizations. For verifying the proposed divider topology, we have designed, fabricated, and measured a microstrip Butterworth filtering power divider. The proposed design approach can also be applied to the design of filtering power dividers with other transmission responses such as Chebyshev and inverse-Chebyshev responses.

A Low-Loss and High-Isolation Transformer-Based mm-Wave SPDT with Integrated Fan-out Wafer Level Packaging

This paper proposes a low-loss and high-isolation transformer (TF)-based mm-wave single-pole double-throw (SPDT) switch. The center-tapped technique is employed at the secondary coil of TF to improve isolation performance. The TF is implemented with the metals in redistribution layers (RDLs) in integrated fan-out (InFO) wafer level packaging technology to obtain low insertion loss (IL) and small chip size as the TF usually dominates the area of SPDT. The control device of the SPDT is realized in 40[Formula: see text]nm bulk CMOS process. The simulated result shows the proposed SPDT achieves a minimum IL of 1.34[Formula: see text]dB and the IL is less than 2.2[Formula: see text]dB at 24–31[Formula: see text]GHz. The isolations are better than 27[Formula: see text]dB between two double-throw ports and better than 20[Formula: see text]dB between single-pole and double-throw ports, respectively. The proposed SPDT has a compact silicon size of 220[Formula: see text][Formula: see text] (with PADs) and its return losses are better than [Formula: see text]9[Formula: see text]dB at 24–31[Formula: see text]GHz and. This work explores a new chip-package co-design method for the SPDT and may have some guidance for the co-design of SPDT and antenna in package (AiP).

Wideband out-of-phase power dividers with improved isolation performance

AbstractA compact wideband out-of-phase power divider (PD) with improved isolation performance is proposed. This divider is formed by connecting an additional stub for isolation to output ports of a traditional Marchand balun with a defected ground structure (DGS) been used. To verify the design, a prototype divider is fabricated and tested. The measured results validate the 53.86% band-width centered at 3.43 GHz with more than 15 dB return loss at all ports, more than 17 dB isolation, respectively.

Isolation Enhancement of Wide-Band MIMO Array Antennas Utilizing Resistive Loading

In this paper, we propose the use of resistor-loaded paired parallel-coupled resonators (PCRs) for mutual coupling reduction and isolation enhancement in wideband MIMO array antennas. It was shown that the isolation enhancement using a conventional PCR structure was drastically degraded in the middle of the frequency band. By placing an optimally designed resistor between the PCRs, we can improve the isolation considerably, compared with the simple PCR structure. Moreover, it could also improve the diversity parameters, such as envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL). The validity of the proposed resistor-loaded PCR technique was verified with ultrawideband array antennas with 1 × 2 and 1 × 4 patch array configurations, achieving a 0.125λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> center-to-center spacing between narrowly spaced patches and isolation better than 25 dB within the range 3-9-GHz without any degradation in its frequency response, radiation patterns, or diversity parameters. The presented results confirm that the proposed technique is suitable in various MIMO systems applicable for wireless local area networks (WLANs), long-term evolution (LTE), and possibly fifth-generation (5G) communication due to the compact size and improved isolation performance.

Novel Metamaterial Compact Planar MIMO Antenna Systems with Improved Isolation for WLAN Application

In this paper, two element multiple input–multiple output (MIMO) meander line antenna systems with improved isolation performance and compact size are proposed and fabricated in WLAN frequency band. To increase isolation among antenna elements, a novel metamaterial spiral S-shaped resonator is embedded between two radiating elements. The proposed resonator has planar configuration and miniaturized size and is capable of blocking electromagnetic propagation between antenna elements by exhibiting negative effective permeability in the desired frequency band. To illustrate and evaluate the design process, two design samples are fabricated and tested in WLAN frequency band and the agreement among measurement and simulation results approves the design method. In the frequency range of 2.38–2.48 GHz, some MIMO communication system requirements like total active reflection coefficient, envelope correlation coefficient and capacity loss are tested on design samples which show satisfactory results, so this method can be employed in designing array antennas for small mobile communication systems. The designed MIMO antenna systems separated by 13.8 mm (less than λ/9), has better than − 40 dB isolation coefficient and near zero correlation coefficient and capacity loss at the operating frequency (2.4 GHz).

A Novel Filtering Balun and Improvement of Its Isolation Performance

A novel filtering balun is proposed in this letter. The filtering balun consists of three half-wavelength uniform-impedance microstrip resonators. Each resonator is coupled to external port through tapped line. Two resonators (called output resonators) connected to balanced output ports are in parallel coupled to the third resonator (called input resonator) connected to the unbalanced input port. The coupling locations have equal-magnitude and out-of-phase voltages, which provides balanced output signals. To improve the isolation performance, a microstrip stub is used to introduce coupling between the output resonators and an isolation resistor is added between the symmetrical position of the microstrip stub and the ground. The isolation resistor can obviously improve isolation performance and has no effect on the balanced output signals. The design is discussed in detail and a prototype filtering balun with center frequency of 2.4 GHz is designed, fabricated, and measured. The measured results have good agreement with the simulated ones, which confirms the novel filtering balun and the design method.

Compact power divider with improved isolation and bandpass response

AbstractThis article presents a compact power divider with band‐pass response and improved isolation by using substrate integrated waveguide (SIW) and defected ground structure (DGS) techniques. The band‐pass response is realized by combining the high‐pass characteristic of SIW and low‐pass feature of DGS. In order to achieve improved isolation performance, a slot which is terminated by four resistors is etched on the top plane of the SIW to balance the three input/output ports. The size of the proposed power divider is relatively small because of the slow‐wave characteristic of DGS. To verify the proposed concept, a prototype power divider with equal power division is fabricated and measured. Measured results show that it has a 3‐dB pass‐band from 8 GHz to 10 GHz and the isolation is higher than 20 dB within the pass‐band.

Experimental characterisation of dry friction isolators for shock and vibration

Shock and vibration are a source of failures in harsh environments such as military, naval and aerospace applications; thus, the use of vibration isolators is extended. Cable isolators are known for their high-energy storage and dissipation properties making them suitable for shock isolation and low frequency vibration. Such isolators present nonlinear stiffness in different directions such as compression, roll and shear, as well as dry friction damping. Although their use is extended, the knowledge regarding their dynamic response under shock loading is very limited. This work presents an overview of the vibration and shock isolation performance of several cable isolators under axial loading. The main contribution of the paper is to investigate and discuss the shock response of the isolators when subjected to pulses of different durations, finding improved isolation performance when compared to an equivalent linear system. Furthermore, a mathematical model based on a Duffing oscillator is proposed as a first approximation, in order to reflect the nonlinear stiffness and predict the shock response, thus facilitating further design and selection of improved shock isolation systems.

The isolation performance of vibration systems with general velocity-displacement-dependent nonlinear damping under base excitation: numerical and experimental study

The study is concerned with isolation performance of a velocity-displacement-dependent (VDD) nonlinear damping, which has arbitrary nonnegative velocity exponent and displacement exponent. Displacement transmissibility of a single-degree-of-freedom (SDOF) vibration system with proposed damping under base excitation is investigated. The implicit amplitude-frequency equation is derived by using the averaging perturbation method. The stability analysis for both integer power law damping and rational powers less than unity in the nonlinearities is performed. The relative and absolute displacement transmissibility is obtained to evaluate the isolation performance. Parametric analysis is carried out to study the influence of damping parameters on the transmissibility. It shows that the proposed damping can not only suppress the response at resonance but also improve isolation performance at high frequencies if the velocity and displacement exponent as well as damping coefficient satisfy some conditions. The condition of a VDD damping that is independent on the excitation amplitude is obtained. Experimental investigation is performed by using a SDOF base excited vibration isolation system possessing a simple velocity feedback control active damper to reproduce the proposed nonlinear damping. The measured results are shown to be in good agreement with theoretical predictions thereby verifying the effects of VDD damping undergoing base excitation. The investigation is capable to enhance understanding of the effects of VDD damping, which will set a foundation for the design and exploitation on beneficial effects of this damping for vibration isolation in engineering systems.

Three‐octave band in‐phase power divider using loosely coupled microstrip lines and microstrip to slotline transitions

A planar microwave in-phase power divider operating over three-octave frequency band is presented. The proposed device is composed of two main parts. The first one is a pair of microstrip–slotline–microstrip transitions introduced to match the impedances at the input port. The second one is a pair of loosely coupled microstrip lines with two isolation resistors to provide improved isolation performance at the output ports over a wide range of frequency band. The device has a compact area of 40 × 40 mm using the substrate RO4003C (dielectric constant of 3.38 and thickness of 0.406 mm). The simulated and experimental results of the developed device show three-octave bandwidths (155% fractional bandwidth) with isolation >15 dB across the investigated band from 1 to 8 GHz. In addition, the device provides a <±2° differential phase between the in-phase output ports across the whole frequency band.

Wideband Four-Way Out-of-Phase Slotline Power Dividers

Two new wideband four-way out-of-phase slotline power dividers are proposed in this paper. The half-wavelength slotlines are employed to construct the presented compact power dividers. Based on the proposed power-dividing circuit, a four-way power divider is implemented with compact size and simple structure. To obtain high isolation among the four output ports and good output impedance matching, another four-way out-of-phase slotline power divider with improved isolation performance is designed by introducing an air-bridge resistor and two slotlines with isolation resistors. The simulated and measured results of the proposed power dividers demonstrate reasonable performance of impedance matching, insertion loss, amplitude balancing, and isolation among the output ports.

Switching Control in Vibration Isolation Systems

In this paper, a switching control approach for active vibration isolation systems is proposed. The switching involves two regimes. In the first regime, no feedback control is applied thereby giving a low sensitivity to noise. In the second regime, active control induces improved disturbance rejection properties, but at the cost of increased noise sensitivity. Conditions for the stability of the switching closed-loop system are formulated whereas the stability analysis provides design rules for tuning the switching controller. Given this novel active vibration isolation approach, improved isolation performance is obtained with substantially less control authority in comparison to the case of linear (or non-switching) feedback control. Performance analysis is based on multi-resolution time-frequency analysis using measurements taken from a commercial vibration isolation system.

Design and control of a hybrid mount featuring a magnetorheological fluid and apiezostack

In this study, a hybrid mount featuring a magnetorheological (MR) fluid and a piezostackis devised to reduce vibrations occuring in dynamic systems which are operated in a widefrequency range. An MR fluid is adopted to improve isolation performance at resonant lowfrequencies, whereas a piezostack actuator is adopted for performance improvement atnon-resonant high frequencies. As a first step, a passive rubber part is manufactured andits dynamic characteristics are experimentally evaluated. By adopting the MR fluid and thepiezostack, semi-active and active actuating mechanisms are devised and theirmathematical models are derived. In particular, the magnetic circuit for MR operationis optimally designed via finite element analysis. After evaluating the dynamiccharacteristics of the manufactured MR device and inertial piezostack actuator, theproposed hybrid mount is then established by integrating them with the rubberpart. Subsequently, a vibration control system is constructed using the proposedhybrid mount, and a sliding mode controller (SMC) is designed to attenuate thevibrations transmitted from the base excitation. Control performances of theproposed mount are experimentally evaluated in time and frequency domains.

MR 유체와 압전 작동기를 이용한 자동차 엔진 마운트의 능동진동제어

This paper presents vibration control of an active hybrid engine mount featuring a magneto-rheological(MR) fluid and a piezostack actuator. The MR fluid is adopted to improve isolation performance at resonant frequencies, while the piezostack actuator is adopted for performance improvement at non-resonant frequencies, especially at high frequencies. Based on some particular practical requirements of engine mounts, the proposed mount is designed and manufactured. The characteristics of rubber element, piezostack actuator and MR fluid are verified for system analysis and controller synthesis. The dynamic model of the proposed mount with a supported mass (engine) is established. In this work, a sliding mode controller is synthesized for the mount system to reduce vibrations transmitted from the engine in a wide frequency range. Computer simulations are performed to evaluate control performances of the proposed active engine mount in time and frequency domains.