Resonant Frequency Band Research Articles

Fusion Execution of NaCl on Tree-Shaped MSA

Fractal tree microstrip antenna utilizing NaCl execution strategy is exhibited in this paper. The fractal tree MSA provides scaling down and multiband operation. NaCl affidavit is a standout amongst the most intriguing method. Trial result on the return loss over the band of 1 to 11 GHz and radiation pattern were exhibited. It is well known that atmospheric corrosion of the metal is accelerated by the sea salt particles near the seashore environment. Objective of the paper is to add NaCl manually on tree-shaped MSA and test the result at different environmental condition. NaCl testimony system unmistakably demonstrates the moving of all resonance frequency bands from high frequencies to low frequencies. VSWR is under 2 for all resonance frequency. Same antenna tried following half year to know the conduct of the MSA and the result is exhibited.

Rolling Bearing Fault Diagnosis with Optimal Resonant Frequency Band Demodulation Based on Squared Envelope Spectral Correlated Kurtosis

Rolling Bearing Fault Diagnosis with Optimal Resonant Frequency Band Demodulation Based on Squared Envelope Spectral Correlated Kurtosis

Fabrication of Phase-Shifted Fiber Bragg Grating by Femtosecond Laser Shield Method

We demonstrated a simple single-exposure method of fabricating phase-shifted fiber Bragg gratings (PSFBGs), in which a non-photosensitive SMF-28 fiber was irradiated by a femtosecond laser beam passing through a uniform period phase mask. The phase-shifted structure in the FBG was formed by shielding a small region of the incident femtosecond laser beam during its irradiation. The fabricated PSFBG exhibited a 0.2 nm narrow resonant frequency band, 88% peak reflectance, and 77% extinction ratio. All-optical switching based on cross-phase modulation was demonstrated in the PSFBG at 1549.625 nm. A switching extinction ratio of more than 40% was achieved for 0.6 kW pulse peak power.

Comparative Research on Characteristics of the Isolation Systems with Dry Friction Damping and with Vicious Damping under Base Excitation

As for the isolation problem of electronic equipments on vehicle, the vibration response characteristics of dry friction damping isolation system under base displacement excitation was analyzed in theory by harmonic balance method, and the displacement response was compared between the isolation systems with dry friction damping and vicious damping separately. The results show that the isolation system with small dry friction damping can’t meet the demands of displacement reduction close to the natural frequency, and it can realize full-frequency vibration isolation by improving dry friction damping when the lock frequency passes beyond the resonance frequency band. The results imply that the damping mechanism of dry friction isolator can’t be described only by dry friction damping, and the composite damping with dry friction and vicious damping is more appropriate.

Broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface

In this paper, a broadband reflective multi-polarization converter based on single-layer double-L-shaped metasurface is proposed. The proposed metasurface can effectively convert linear-polarized (TE/TM) incident wave into the reflected wave with three different polarizations within the frequency bands of 5.5–22.75 GHz. Based on the electric and magnetic resonant features of the double-L-shaped structure, the proposed metasurface can convert linearly polarized waves into cross-polarized waves at three resonant frequency bands. Furthermore, the incident linearly polarized waves can be effectively converted into left/right handed circular-polarized (LHCP and RHCP) waves at other four non-resonance frequency bands. Thus, the proposed metasurface can be regarded as a seven-band multi-polarization converter. The prototype of the proposed polarization converter is analyzed and measured. Both simulated and measured results show the 3-dB axis ratio bandwidth of circular polarization bands and the high polarization conversion efficiency of cross-polarization bands when the incident wave changes from 0° to 30° at both TE and TM modes.

Spiking resonances in models with the same slow resonant and fast amplifying currents but different subthreshold dynamic properties

The generation of spiking resonances in neurons (preferred spiking responses to oscillatory inputs) requires the interplay of the intrinsic ionic currents that operate at the subthreshold voltage level and the spiking mechanisms. Combinations of the same types of ionic currents in different parameter regimes may give rise to different types of nonlinearities in the voltage equation (e.g., parabolic- and cubic-like), generating subthreshold (membrane potential) oscillations patterns with different properties. These nonlinearities are not apparent in the model equations, but can be uncovered by plotting the voltage nullclines in the phase-plane diagram. We investigate the spiking resonant properties of conductance-based models that are biophysically equivalent at the subthreshold level (same ionic currents), but dynamically different (parabolic- and cubic-like voltage nullclines). As a case study we consider a model having a persistent sodium and a hyperpolarization-activated (h-) currents, which exhibits subthreshold resonance in the theta frequency band. We unfold the concept of spiking resonance into evoked and output spiking resonance. The former focuses on the input frequencies that are able to generate spikes, while the latter focuses on the output spiking frequencies regardless of the input frequency that generated these spikes. A cell can exhibit one or both types of resonances. We also measure spiking phasonance, which is an extension of subthreshold phasonance (zero-phase-shift response to oscillatory inputs) to the spiking regime. The subthreshold resonant properties of both types of models are communicated to the spiking regime for low enough input amplitudes as the voltage response for the subthreshold resonant frequency band raises above threshold. For higher input amplitudes evoked spiking resonance is no longer present in these models, but output spiking resonance is present primarily in the parabolic-like model due to a cycle skipping mechanism (involving mixed-mode oscillations), while the cubic-like model shows a better 1:1 entrainment. We use dynamical systems tools to explain the underlying mechanisms and the mechanistic differences between the resonance types. Our results demonstrate that the effective time scales that operate at the subthreshold regime to generate intrinsic subthreshold oscillations, mixed-mode oscillations and subthreshold resonance do not necessarily determine the existence of a preferred spiking response to oscillatory inputs in the same frequency band. The results discussed in this paper highlight both the complexity of the suprathreshold responses to oscillatory inputs in neurons having resonant and amplifying currents with different time scales and the fact that the identity of the participating ionic currents is not enough to predict the resulting patterns, but additional dynamic information, captured by the geometric properties of the phase-space diagram, is needed.

누설전자파 측정을 위한 초광대역 로그주기 안테나의 소형화

In this paper, to implement the electromagnetic wave environment and solve electromagnetic compatibility(EMC) problem, miniaturization of ultra-wide band log periodic dipole antenna for measurement was investigated. In addition, in oder to improve the signal-to-noise ratio in high frequency band, balun was connected to the antenna to stabilize the operation of the differential mode antenna and the single mode coaxial cable. To minimize the total size and to increase bandwidth of the antenna, a fat dipole structure was used for the resonance frequency band below 4 GHz and a general dipole shape was used for that above 4 GHz. The bandwidth of the proposed antenna was represented from 0.6 GHz to 8.0 GHz with a ratio bandwidth of 12.3 : 1. Measured peak gain varies from 5.7 dBi to 9.1 dBi, and a half power beamwidth was presented from 29.4° to 100.2° in operating range.

An Improved Resonant Frequency Based Systematic LCL Filter Design Method for Grid-Connected Inverter

Resonant frequency of an LCL filter in a grid-connected inverter is an important factor for control stability and grid-injected current quality. However, the constraints on resonant frequency are usually considered as an afterthought in conventional filter design methods. The fact that resonant frequency is affected by both internal and external factors during operation makes it even more critical. Hence, an improved resonant frequency based systematic LCL filter design method is presented in this paper. A resonant frequency band is identified by considering grid-voltage harmonics and control stability boundary. The variation in resonant frequency due to inductive line impedance as well as magnetic permeability of inductor core is taken into account to define the constraints on LCL parameters. The LCL parameters are then systematically derived from the identified constraints with almost no iteration. A division–summation (D-Σ) digital control method is used to validate the design method. Experimental results measured from a 5-kW single-phase grid-connected inverter have verified the effectiveness of the LCL filter design method over conventional methods.

A tri‐band slot antenna loaded with split ring resonators

AbstractA compact tri‐band slot antenna with independent tuning capability of its resonant frequencies is proposed in this article. A microstrip line fed square slot is loaded with split ring resonators (SRR) to obtain multiband characteristics. The slot is designed to resonate at 2.6 GHz. Two SRRs with single and multiple splits are loaded with the slot, which provide additional resonances at 4.3 and 4.7 GHz, respectively. Parametric analysis of the antenna shows that its resonance frequencies are controlled independently. The proposed antenna is fabricated on an FR4 substrate with a size of 60 × 60 × 1.56 mm2. The proposed design offers stable omnidirectional patterns and >3.8 dBi at all the resonating frequency bands.

Bearing Fault Diagnosis using Singular Spectrum Analysis-Based Envelope Detection

Rolling element bearings are critical components in rotating machinery and it is important to monitor their health and detect their faults in early stage during their operations. The vibration energy generated by the faults in rolling element bearings is usually small comparing to that of other rotating components such as rotors/shafts and gears in mechanical systems. Envelope analysis is a widely used method in bearing fault diagnosis. The major challenge in envelope analysis is the identification of resonance frequency band for narrow-band filtering before applying envelope operation. In this paper, a method combining singular spectrum analysis (SSA) and envelope analysis is proposed for diagnosing the rolling element bearing faults. The SSA is utilized to decompose the bearing vibration signal into a set of eigentriples (principle components), and then a subset of the eigentriples that encompass the dominant variation in the original signal is selected for signal reconstruction. Envelope analysis is then applied to the reconstructed signal to extract the modulation information that caused by the bearing faults. The proposed SSA-based envelope analysis is applied to the data sets of the bearing data center at Case Western Reserve University (CWRU), and the results are compared with that of the widely used Kurtogram-based envelope analysis. The results show that the SSA-based envelope analysis is more effective than the Kurtogrambased envelope analysis in bearing fault diagnosis.

Novel Electrostatically Tunable Frequency Selective Surface with PZT/FeGaB Films

Strong magnetoelectric (ME) coupling can be realized in multiferroic heterostructures, which have led to a variety of devices. Here, a novel electrostatically tunable frequency selective surface (FSS) with PZT/FeGaB films is reported, which shows a high resonant frequency tunability. A high X to Ku band resonant frequency tunability of f = 2.75 GHz or f/f= 24% was demonstrated in the FSS with PZT/FeGaB films, which was 10 times of the similar FSS structure with only FeGaB film. This electrostatically tunable FSS with strong ME coupling will provide great opportunities for more energy efficient, less noisy, compact and light-weight microwave devices with frequency tunabilities.

Size miniaturization of microstrip antenna embedded with open-ended ground slots

A compact rectangular microstrip antenna embedded with open-ended ground slots is presented in this paper. Three equal open-ended ground slots have been incorporated inside the ground plane in order to excite the antenna with a lower order resonant mode. On variation of the length parameter of the middle slot of the antenna, a resonant mode of lower order has been obtained near 1.52 GHz. The maximum size reduction of the designed structure is obtained, considering the lower band resonant frequency obtained is about 85.83% with a fractional bandwidth of 6.97%. The simple configuration has been fabricated on low-cost FR-4 substrate material. The proposed low-profile triple band microstrip patch obeys all the necessary standards prescribed for wireless communication and, therefore, finds its applicability in multiband wireless communication systems.

Compact Mobile Quad-Band Slot Antenna Design for GPS L1, WiMAX, and WLAN Applications

In this paper, an asymmetric compact multiband slot antenna is proposed for global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) applications. The top plane, a ground is composed of a rectangular slot with a trapezoidal-like stub, an inverted U-shaped slot at the right side of the rectangular slot, an inverted L-shaped slot at the left side of the rectangular slot, and three stubs. The proposed antenna is fed by an asymmetric cross-parasitic strip on the bottom plane. By properly designing the slots and stubs, four resonant frequency bands are achieved with -10 dB reflection coefficient bandwidths of 50 MHz, 400 MHz, 390 MHz, and 830 MHz in the 1.57 GHz GPS band, 2.4 GHz WLAN band, 3.5 GHz WiMAX band, and 5.5 GHz WLAN bands, respectively. The antenna has a total compact size of 13 mm × 32 mm × 0.8 mm. Simulated and measured results indicate that the proposed antenna has sufficient bandwidth and good radiation performance in each band.

A Study of Dual/Triple-Band Microstrip-Fed Slot Antenna Design for WLAN/WiMAX Communication Systems

This paper presents a study of dual/triple-band simple slot antenna fed by microstrip line for WLAN and WiMAX communications systems. The first proposed antenna consists of a rectangular slot with rectangular-ring strip at the centre of a rectangular ground plane and microstrip line feed at the centre for excitation. The simulation results of the return loss of the first proposed antenna can cover the frequency range at 2.32-2.48 GHz (WLAN 2.4 GHz), and 5.49-6.11 GHz (WLAN/WiMAX 5.8 GHz). The first proposed antenna is extended by inserting an L-shaped slot in rectangular-ring strip to create third frequency WiMAX at 3.5 GHz band and it can control resonant frequency band operations. The simulation results of the proposed antenna are analyzed by using IE3D Software. The measurement results of triple-band slot antenna of return loss (S11), the first resonant frequency has an impedance bandwidth of 240 MHz (2.45-2.69 GHz), which covers the 2.5 GHz WLAN/WiMAX bands. The second resonant frequency has an impedance bandwidth of 170 MHz (3.45-3.62 GHz) at 3.5 GHz frequency band (WiMAX 3.5 GHz). The third resonant frequency has an impedance bandwidth of 600 MHz (5.7-6.3 GHz), covering the 5.8 GHz WLAN/WiMAX bands. Moreover, the proposed antenna can control a shift of the resonant frequency. The radiation patterns of the proposed antenna in E-plane and the H-plane are bi-directional and omni-directional.

Design and analysis of a self-biased broadband magnetoelectric cantilever operated at multi-frequency windows

Magnetoelectric (ME) composites with self-biased and wide resonance frequency band properties are promising candidates for magnetic field sensor and energy harvester. Here, we present a ME cantilever by in-series connecting a few SrFe12O19/Metglas/Pb(Zr,Ti)O3 components. Due to the in-built magnetic bias of SrFe12O19, the ME cantilever shows self-biased property. Meanwhile, by merging the resonance responses of the in-series ME components together, the ME cantilever presents multi-wide resonance bands (i.e., 500 Hz ∼ 700 Hz, 3.3 kHz ∼ 4.4 kHz and 44 kHz ∼ 70 kHz). In these three wide frequency windows, the ME voltage coefficients (αV) of the ME cantilever are higher than 40 mV/Oe, 115 mV/Oe and 400 mV/Oe, respectively.

Optimal Resonant Band Demodulation Based on an Improved Correlated Kurtosis and Its Application in Bearing Fault Diagnosis.

The kurtosis-based indexes are usually used to identify the optimal resonant frequency band. However, kurtosis can only describe the strength of transient impulses, which cannot differentiate impulse noises and repetitive transient impulses cyclically generated in bearing vibration signals. As a result, it may lead to inaccurate results in identifying resonant frequency bands, in demodulating fault features and hence in fault diagnosis. In view of those drawbacks, this manuscript redefines the correlated kurtosis based on kurtosis and auto-correlative function, puts forward an improved correlated kurtosis based on squared envelope spectrum of bearing vibration signals. Meanwhile, this manuscript proposes an optimal resonant band demodulation method, which can adaptively determine the optimal resonant frequency band and accurately demodulate transient fault features of rolling bearings, by combining the complex Morlet wavelet filter and the Particle Swarm Optimization algorithm. Analysis of both simulation data and experimental data reveal that the improved correlated kurtosis can effectively remedy the drawbacks of kurtosis-based indexes and the proposed optimal resonant band demodulation is more accurate in identifying the optimal central frequencies and bandwidth of resonant bands. Improved fault diagnosis results in experiment verified the validity and advantage of the proposed method over the traditional kurtosis-based indexes.

Spectral prediction and control of blast vibrations during the excavation of high dam abutment slopes with millisecond-delay blasting

In hydropower projects in Southwest China, large-scale, high-intensity blasts are required to excavate high rock slopes. In these cases, traditional prediction and control methods for blast vibrations are invalid. Thus, a method to predict the time history of blast vibrations on high slopes is proposed, and a blast vibration spectral control scheme based on this method is presented. Additionally, a case study for the abutment slope excavation of the Xiluodu hydropower project is presented. The results indicate that if the delay interval is <20ms or >50ms, a large amount of energy is distributed in the resonant frequency band of the slope; with optimized delay interval of 20–25ms and 45–50ms, the low-frequency compositions of blast vibrations are considerably fewer, and spectral control can be implemented more effectively. Delay intervals of 25 and 50ms are adopted in practice considering the detonator limitation.

Compound faults detection in gearbox via meshing resonance and spectral kurtosis methods

Kurtosis-based impulsive component identification is one of the most effective algorithms in detecting localized faults in both gearboxes and rolling bearings. However, if localized faults exist in both gear tooth and rolling bearing simultaneously it is difficult to tell the differences between the two types of defects. As such, this study proposes a new method to solve the problem by using the meshing resonance and spectral kurtosis (SK) algorithms together. In specific, the raw signal is first decomposed into different frequency bands and levels, and then the corresponding Kurtogram and MRgram are calculated via the fault SK analysis and the meshing index. Furthermore, the resonance frequency bands induced by localized faults of the gear tooth and rolling bearing are separately identified by comparing the Kurtogram and the MRgram. Finally, the compound faults are respectively detected using envelope analysis. The effectiveness of the proposed method has been validated via both simulated and experimental gearboxes vibration signals with compound faults.

A Linear Array Antenna of Microstrip Patch Antennas Fed by the Open-End of Coplanar Waveguides

In this study, we constructed a 4-element linear array antenna using four 20 GHz band microstrip patch antennas with a structure such that the signal is fed to the patch antennas from open-end coplanar waveguides without contact. We investigated factors related to the design of linear array patch antennas. To adjust the maximum radiation direction and reduce return loss, we optimized the spacing between the elements and their shape. With an element spacing of 11.50 mm, patch width of 3.90 mm, and patch length of 4.15 mm, we obtained a resonance frequency of 20.05 GHz and a return loss of -29.59 dB at the resonance frequency. However, in the case of a 4-element linear array antenna structure, undesired resonances occurred in frequency bands other than the design resonance frequency band of 20 GHz. To suppress these undesired resonances and obtaining stable operation at the design frequency, we propose a new structure in which the feed line is loaded with a short stub, and show through computer simulations that the occurrence of undesired resonances can be sufficiently suppressed. Furthermore, we demonstrate the problem of radiation gain reduction caused by introducing a short stub, propose a design method for a new structure in which the feed line has slits between the stubs, and show improvement of the antenna gain by 0.5 dBi.

Time-Frequency Analysis of Torsional Vibration Signals in Resonance Region for Planetary Gearbox Fault Diagnosis Under Variable Speed Conditions

Translational vibration-based methods have been widely used for machinery fault diagnosis. However, because of the unique gear configuration and complex kinetics, planetary gearbox translational vibration signals have complex modulation features due to gear faults and time-varying vibration transmission paths. This results in complex frequency components of translational vibrations, and adds difficulty to gear fault signature extraction. Under variable speed conditions, the resultant time-variant frequency components and complex sidebands may overlap in frequency domain, thus making it more difficult to pinpoint fault features. To address this issue, torsional vibration signals are exploited, because they are free from the extra modulation effect due to time-varying transmission paths and have simpler frequency contents. Gear faults generate impacts, thus exciting resonances and leading to modulations on resonances. Therefore, torsional resonance frequency band is concentrated to extract gear fault information. The time-variant but symmetric sideband characteristics in the resonance region are derived based on the explicit time-varying amplitude modulation and frequency modulation signal model. Resonance frequencies are identified under variable speed conditions by virtue of their independence on running conditions. Furthermore, time-frequency analysis is utilized to extract time-variant gear fault frequencies. The proposed method is validated using both numerical simulation and lab experimental data. Localized faults of the sun, planet, and ring gears are diagnosed under variable speed conditions.