Resonant Frequency Band Research Articles

Transparent Microstrip Patch Antennas With Multilayer and Metal-Mesh Films

This letter presents transparent microstrip patch antennas made of two types of transparent conductive films, which are multilayer film (MLF; IZTO/Ag/IZTO) and metal-mesh film (MMF; Cu). The sheet resistance levels of the MLF and MMF are 2.52 and 0.18 Ω/□. The transparencies of the MLF and MMF are over 80% and 60% at a 550-nm wavelength, respectively. The design and dimensions of the antennas follow the conventional simple microstrip patch antenna. A transparent acryl substrate is used for the proposed transparent antennas. The conductive parts of the proposed antennas are also made of copper sheets (CS; case 1) for the performance comparison to two types of transparent antennas made of MLF (case 2) and MMF (case 3). The resonance frequency band of the antennas is 2.4–2.5 GHz for Wi-Fi service. The case-1, case-2, and case-3 antennas have peak gains of 4.75, −4.23, and 2.63 dB and have radiation efficiencies of 66.32%, 7.76%, and 42.69% at the center frequency of the Wi-Fi service band (2.45 GHz), respectively.

Polarization‐Induced Chirality in Metamaterials via Optomechanical Interaction

A novel type of metamaterial is introduced, where the structural symmetry can be controlled by optical forces. Since symmetry sets fundamental bounds on the optical response, symmetry breaking changes the properties of metamaterials qualitatively over the entire resonant frequency band. This is achieved by a polarized pump beam, exerting optical forces which are not constrained by the structural symmetry. This new concept is illustrated for a metasurface composed of zig‐zag chains of dipole meta‐atoms, in which a highly asymmetric optical force exists for an appropriate incident polarization. The effect is employed to transform a planar achiral metasurface into a stereoscopic chiral structure. Importantly, the handedness of the induced chirality can be actively switched by changing the incident polarization. The proposed concept can be employed to achieve dynamic spatial control of metamaterials and metasurfaces at infrared and optical frequencies with subwavelength resolution.

Fault diagnosis for wind turbine planetary ring gear via a meshing resonance based filtering algorithm

Identifying the differences between the spectra or envelope spectra of a faulty signal and a healthy baseline signal is an efficient planetary gearbox local fault detection strategy. However, causes other than local faults can also generate the characteristic frequency of a ring gear fault; this may further affect the detection of a local fault. To address this issue, a new filtering algorithm based on the meshing resonance phenomenon is proposed. In detail, the raw signal is first decomposed into different frequency bands and levels. Then, a new meshing index and an MRgram are constructed to determine which bands belong to the meshing resonance frequency band. Furthermore, an optimal filter band is selected from this MRgram. Finally, the ring gear fault can be detected according to the envelope spectrum of the band-pass filtering result.

A Comparison of Minkowski, Compact Multiband and Microstrip Fractals with Meander Fractal Antenna

This paper presents the comparison of existing fractal antennas with the proposed fractal antenna on the basis of performance parameters such as return loss and gain. Proposed antenna is designed on FR4 glass epoxy substrate with thickness 1.6mm and dielectric constant 4.4. The HFSS V13 software is used to design and simulate the proposed fractal antenna. By observing the simulated results of proposed antenna it has been concluded that it works on six resonant frequency bands with the maximum value of gain 8.8dB at 3.14GHz frequency band. The existing antenna works on maximum two frequency bands of operation. Due to the multiband characteristics of proposed antenna, it can be used for different wireless applications as per FCC standards.

Sharp increase of microwave absorption in nonequilibrium MnZn- and NiZn-nanoferrites

We study microwave electromagnetic absorption in films containing (Mn,Zn)Fe2O4 and (Ni,Zn)Fe2O4 spinel nanoparticles in equilibrium and nonequilibrium spin states. The nonequilibrium spin state has been formed by the action of the alternating magnetic field with the frequency of 1 Hz. It is found that in the nonequilibrium state the microwave absorption is strongly enhanced. The microwave losses are increased by 78 times for the film with MnZn-spinel nanoparticles and by 12 times for the film containing NiZn-nanoferrite. The microwave-absorption-increase effect is observed in the central part of the ferromagnetic resonance frequency band. This frequency band of the microwave absorption enhancement is narrower than the ferromagnetic linewidth in the equilibrium state.

Dipole‐slot‐dipole metasurfaces

A complementary frequency selective surface (CFSS) can be formed on the basis of Babinet’s principle. It consists of an array of slots separated from an array of dipoles by a thin dielectric substrate. This study shows that by adding an extra layer of dipoles to a CFSS capacitance can be added to the structure, which leads to a decrease in its resonant frequency. This new structure is called a dipole-slot-dipole metasurface (MTS) and it has unit-cell dimensions of l/10 × l/10 × l/333, where l is representing the free space wavelength. The dipole-slot-dipole MTS has been fabricated and measured. The study also reports on its equivalent circuit; and the effects of the length of the dipoles on the added layer and their alignment on the pass band resonant frequency of the dipole-slot-dipole MTS.

Parametric study on nonlinear vibration of composite truss core sandwich plate with internal resonance

Nonlinear vibrations of carbon fiber reinforced composite sandwich plate with pyramidal truss core are investigated. The governing equation of motion for the sandwich plate is derived by using a Zig-Zag theory under consideration of geometrically nonlinear. The natural frequencies of sandwich plates with different dimensions are calculated and compared with those obtained from the classic laminated plate theory and Reddy’s third-order shear deformation plate theory. The frequency responses and waveforms of the sandwich plate when 1:3 internal resonance occurs are obtained, and the characteristics of the internal resonance are discussed. The influences of layer number of face sheet, strut radius, core height and inclination angle on the nonlinear responses of the sandwich plate are analyzed. The results demonstrate that the strut radius and inclination angle mainly affect the resonance frequency band of the sandwich plate, and the layer number and core height not only influence the resonance frequency band but also significantly affect the response amplitude.

Global stabilization of high-energy response of a nonlinear wideband electromagnetic energy harvester

This paper presents a resonance-type vibration energy harvester with a Duffing-type nonlinear oscillator which is designed to perform effectively in a wide frequency band. For the conventional linear vibration energy harvester, the maximum performance of the power generation and its bandwidth are in a relation of trade-off. Introducing a Duffing-type nonlinearity can expand the resonance frequency band and enable the harvester to generate larger electric power in a wider frequency range. However, since such nonlinear oscillator may have coexisting multiple steady-state solutions in the resonance band, it is difficult for the nonlinear harvester to maintain the high performance of the power generation constantly. The principle of self-excitation and entrainment has been utilized to give global stability to the high-energy orbit by destabilizing other unexpected low-energy orbits by introducing a switching circuit of the load resistance between positive and the negative values depending on the response amplitude of the oscillator. In this paper, an improved control law that switches the load resistance according to a frequency-dependent threshold is proposed to ensure the oscillator to respond in the high-energy orbit without ineffective power consumption. Numerical study shows that the steady-state responses of the harvester with the proposed control low are successfully kept on the high-energy orbit without repeating activation of the excitationmode.

Design and Experimental Verification of Vibration Suppression Device on the Lift of Wheelchair-accessible Vehicles

In recent years, the number of wheelchair-accessible vehicles has increased with the aging of the population. Such vehicles are effective in reducing the burden on caregivers because the wheelchair user does not have to move from his/her wheelchair to a seat of the vehicle. Wheelchair-accessible vehicles are expected to be widely used in the future. However, wheelchair users have reported poor ride comfort. It is thus necessary to suppress the vibration of the vehicle considering the wheelchair user. We designed a passive damping device on the lift of wheelchair-accessible vehicles to improve the ride comfort for wheelchair users. The vibration due to road disturbances reaches the wheelchair user's body through the vehicle and wheelchair. Our control device decreases the acceleration of the torso and improves the ride comfort by ensuring that the frequency of the vibration reaching the wheelchair user differs from the resonance frequency band of the acceleration of the torso, which is the body part that feels the most discomfort. The effectiveness of the control device is verified experimentally.

Honeycomb-shaped meta-structure for minimizing noise radiation and resistance to cooling fluid flow of home appliances

Meta-structures composed of honeycomb-shaped unit cells were built to have high sound-proof and heat-exhaust performance. Each unit cell operates as a Helmholtz resonator (HR) and a lumped inertance muffler (LIM), resulting in sound energy dissipation at specific tonal and broadband frequencies and minimal noise transmission. This cover structure allowed heat-exhaust through the open cross-sectional area. The acoustic characteristics of the meta-structure fabricated using ABS were measured by the four microphone method. The bandgap at specific frequencies and noise reduction at high frequencies were investigated. The significant change of negative effective mass density and the purely complex value of the wave speed were measured at the resonant frequency band of HR. The theoretical model was suggested to analyze the noise reduction mechanism. The designed meta-structure was applied as the covers of the refrigerator machine room and the top-loading washing machine for demonstrating a practical noise control applications. The suggested structures were designed to meet same geometric constraints as the original cover both in dimensions and open area for heat exhaust. To evaluate the noise reduction performances, the sound radiations from the operating refrigerator and washing machine were measured. The noise transmitted through the panel was significantly reduced by using the proposed cover in the specific frequency bands. For the washing machine, the efficiency depended on the type of the operating process. Noise reduction was large during the fill and wash process, whereas, minimal during drain and spin process. Because the resonance and cut-off frequencies of HR and LIM were designed as 570 and 300Hz, respectively, the effectiveness was minimal for low frequency sounds. The temperature of the operating compressor of refrigerator and the spinning motor of washing machine showed minimal increase suggesting identical heat exhaust performances. The suggested meta-structure induced large noise reduction without influencing heat exhaust by similar open area for fluid flows as the original cover.

Quasistatic dipole in magnetized plasma in resonance frequency band. Response of the receiving antenna, and charge distribution on the antenna wire

The paper discusses issues related to the radiation and reception of quasi-electrostatic waves by short antennas in resonance conditions (in the whistler range) in magnetized plasma. First, the response of the receiving antenna on the incident field of slow quasipotential waves is analyzed. It made it possible to explain in detail the results of the two-point rocket experiment OEDIPUS-C in the Earth’s ionosphere. Second, the problem of the charge distribution along the short transmission (reception) dipole antenna is considered. The corresponding integral equation is obtained and solved analytically. The impedance of the antenna is found. It is shown that in the majority of cases, charge distribution along the dipole length can be considered constant.

An asymmetric coplanar strip-fed 7-shaped monopole antenna for miniaturized communication systems

A compact asymmetric coplanar strip (ACS)-fed monopole antenna for miniaturized communication systems is proposed. It consists of an ACS-fed 7-shaped monopole, a partial ground plane, and an FR4 substrate. The proposed antenna occupies a very compact size of only 30 × 13 mm2 which accords with the development trend toward miniaturized electronic components. The 7-shaped monopole can be considered as a combination of three parts—a rectangular strip on the top, a trapezoidal strip in the center, and a straight microstrip feed line at the bottom—which generates two separate resonant frequency bands. By introducing an open-ended T-shaped slot in the rectangular strip, a new resonant mode can be excited. Detailed descriptions of the design evolution as well as the parametric study are given to better understand the mechanisms of the proposed antenna. Experimental results demonstrate that it can provide a triple-band frequency range compatible with the 2.4/5.2/5.8 GHz WLAN (2.4–2.485, 5.15–5.35, and 5.725–5.825 GHz) and 3.5/5.5 GHz WiMAX (3.4–3.7 and 5.25–5.85 GHz) operating bands. Furthermore, stable radiation patterns with satisfactory gains make it a good candidate as an internal antenna for compact multiband communication systems. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1566–1572, 2016

Vibration mechanisms of spur gear pair in healthy and fault states

The vibration frequency components of gear system are complicated and changeful, some of those are even hard to explain. Based on the dynamic equations of a single-stage gear pair and some reasonable simplifications, frequency responses of the gear pair in healthy state and those suffering from different faults are analyzed, respectively. The excitation sources of vibration frequency components such as rotational frequency harmonics, mesh frequency harmonics, modulation sidebands and resonance frequency bands are investigated accordingly. The causes of the asymmetrical modulation sidebands around the mesh frequency harmonics, which are commonly appeared in the vibration spectrum of gear system, are explained. The effectiveness of the theoretical deductions is confirmed by dynamic simulations and experimental results.

Nonlinear resonant magnetoelectric coupling model for dual-peak phenomenon in magnetoelectric laminates

We investigated the dual-peak phenomenon in the response curve of the magnetoelectric (ME) coupling coefficient versus magnetic field for Terfenol-D/PZT/Terfenol-D tri-layer magnetoelectric laminated composites. Using nonlinear constitutive relations for the magnetostrictive material, an expression for the resonance ME coefficient that considers nonlinear resonance mechanical loss is established with the aid of the equivalent circuit method. The established model effectively predicts the complex behavior related to dual-peak phenomenon in regard to pre-stress, bias magnetic field, frequency of the alternating magnetic field, and nonlinear mechanical loss, and explains the origin of the dual peaks. The response curves obtained are consistent with experimental results. It can be found from the further predictions that in a given resonance frequency band, selecting an appropriate pre-stress can regulate two peaks in dual-peak curve, so that a giant ME coupling effect is obtained on the first peak, or a stronger resonance peak is achieved by adjusting stress to merge two peaks. With our resonance ME dual-peak model, we also demonstrate a giant ME coupling by regulating the dual-peak resonances by pre-stress engineering.

Design and Study the Effect of Switching in Microstrip Patch Antenna for Cognitive Radio Applications

Design of microstrip antenna having switches for accomplishing frequency reconfigurability is proposed. The proposed design is having six resonating frequency bands between 3.34GHz to 3.67GHz which were achieved by using different switching configurations. Switches were assumed as ideal so as to study the simulated results of the antenna .The antenna design was made on the FR4 substrate having height of 1.6mm.The overall size of the antenna is 39×40mm2. Simulated results are utilized to validate performance of antenna. The radiation pattern, return loss and measured bandwidth are presented in the paper. Simulated results presented in this paper make the antenna are appropriate for applications such as cognitive radio which requires sensing of spectrum to use the bandwidth in an optimal manner.

Gain and directivity enhancement of microstrip antenna loaded with multiple splits octagon-shaped metamaterial superstrate

This paper presents a novel multiple splits octagon-shaped metamaterial which exhibits double left-handed frequency bands roughly from 9.25 GHz to 9.68 GHz and from 15.28 GHz to 15.36 GHz derived from the transmission characteristics by homogenization retrieval method. Two conventional microstrip patch antennas whose resonance frequency bands are located at the first left-handed frequency band and the second one respectively are designed to further investigate the influence by loading the proposed metamaterial as its superstrate. HFSS simulation numerical results indicate that the far field radiation directivity half-power bandwidth(HPBW) of the E-plane and H-plane have reduced by 64%, 63.7% and 59.4%, 59%, and the maximal gain increases from 8.251 dB to 11.024 dB and from 8.5432 dB to 11.9653 dB respectively after loading with the multiple splits octagonal metamaterial superstrate.

DUAL-BAND BANDPASS FILTER USING COMPOSITE COUPLING STRUCTURE FOR CPW/MICROSTRIP

By using a composite coupling structure for coplanar waveguide (CPW)/microstrip, a new dual-band bandpass filter (DBBPF) stacking inverted Y-shaped CPW resonators and rectangular ring resonators is proposed. Two resonant frequency bands are simultaneously excited by the CPW feed line. However, it can be convenient to tune individually. Several transmission zeros are realized to improve the selectivity of the filter and achieve wide stopband rejection. Good agreement between simulated and measured results demonstrates the validity of this DBBPF.

Simulation of High-Transmission Chiral Metamaterial with Impedance Matching to a Vacuum**Supported by the National Natural Science Foundation of China under Grant No 61205011.

For a previously simulated eight-broadband negative-refraction-index chiral metamaterial, we use S-parameter retrieval methods to determine the complex effective permittivity, permeability, and the impedance. We also calculate the figure of merit, which is defined as the ratio of the real and the imaginary refraction components, and compare it with those of fishnet metamaterials. The simulation results show that our chiral metamaterial exhibits high transmission and impedance matching to a vacuum. Also, we determine that the electric and magnetic dipoles of the surface plasmons play an important role in determining the nine resonance frequencies. Therefore, this investigation provides an experimental basis for developing metamaterial devices with multiple and broad resonance frequency bands.

Sparse Signal Representations of Bearing Fault Signals for Exhibiting Bearing Fault Features

Sparse signal representations attract much attention in the community of signal processing because only a few coefficients are required to represent a signal and these coefficients make the signal understandable. For bearing faults’ diagnosis, bearing faults signals collected from transducers are often overwhelmed by strong low-frequency periodic signals and heavy noises. In this paper, a joint signal processing method is proposed to extract sparse envelope coefficients, which are the sparse signal representations of bearing fault signals. Firstly, to enhance bearing fault signals, particle swarm optimization is introduced to tune the parameters of wavelet transform and the optimal wavelet transform is used for retaining one of the resonant frequency bands. Thus, sparse wavelet coefficients are obtained. Secondly, to reduce the in-band noises existing in the sparse wavelet coefficients, an adaptive morphological analysis with an iterative local maximum detection method is developed to extract sparse envelope coefficients. Simulated and real bearing fault signals are investigated to illustrate how the sparse envelope coefficients are extracted. The results show that the sparse envelope coefficients can be used to represent bearing fault features and identify different localized bearing faults.

Early Fault Diagnosis of Bearings Using an Improved Spectral Kurtosis by Maximum Correlated Kurtosis Deconvolution.

The early fault characteristics of rolling element bearings carried by vibration signals are quite weak because the signals are generally masked by heavy background noise. To extract the weak fault characteristics of bearings from the signals, an improved spectral kurtosis (SK) method is proposed based on maximum correlated kurtosis deconvolution (MCKD). The proposed method combines the ability of MCKD in indicating the periodic fault transients and the ability of SK in locating these transients in the frequency domain. A simulation signal overwhelmed by heavy noise is used to demonstrate the effectiveness of the proposed method. The results show that MCKD is beneficial to clarify the periodic impulse components of the bearing signals, and the method is able to detect the resonant frequency band of the signal and extract its fault characteristic frequency. Through analyzing actual vibration signals collected from wind turbines and hot strip rolling mills, we confirm that by using the proposed method, it is possible to extract fault characteristics and diagnose early faults of rolling element bearings. Based on the comparisons with the SK method, it is verified that the proposed method is more suitable to diagnose early faults of rolling element bearings.