Original Resonant Frequency Research Articles

Multifunctional dual stimuli-triggered metadevice in terahertz regime

Multifunctional metadevices have garnered substantial attention because of their optical characteristics for operation within the terahertz regime. However, metasurfaces have unalterable geometrical configurations that represent a limitation in this context, thus necessitating dynamic adjustability of the structures. In this study, a development strategy is used that involves a dual stimuli-responsive programmable terahertz metamaterial based on indium oxide (In2O3). When exposed to light irradiation, the resonant frequency of this metamaterial undergoes a red shift of up to approximately 100 GHz when compared with the original resonant frequency. The processed terahertz signal is then used for binary coding as well as computer color coding through two active stimulation methods. This dual stimuli-triggered metamaterial concept can be extended to other frequency bands and thus offers a promising route toward electromagnetic information processing applications.

Cubic root-locus format for structures with a local viscous damping device

The tuning and efficiency of a local viscous damper on a flexible structure is described via an approximate representation of the characteristic equation in the form of a cubic polynomial. Increasing the viscosity to the limit of locking of the device typically leads to an increased modal resonance frequency, but may lead to a decrease. A cubic approximation is developed covering both cases in which the effect of the non-resonant modes is represented by an equivalent stiffness or inertia term, respectively. The magnitude of the stiffness or inertia parameter is determined by the change in resonance frequency following from locking of the device, and thus the cubic root-locus curve is determined by only two parameters: the original undamped resonance frequency, and the frequency after locking. The length parameter along the curve is given by a suitably scaled non-dimensional damping parameter. It is demonstrated that when introducing the geometric mean of the unlocked and locked frequencies the complex root locus curve for increasing damping parameter consists of inverse points with respect to a circle with the geometric mean frequency as radius, and furthermore the inverse points correspond to reciprocal values of the normalized damping parameter. The explicit results of optimal damper tuning and the resulting structural damping enable direct design based solely on the three parameters, that can typically be extracted from a standard finite element analysis of the structure. Two examples demonstrate the accuracy of the cubic format, and clarify the reason for decrease of the modal frequency by damping for certain cases.

Harmonic Resonance Analysis of Shale Gas Distribution Network with Phased Load

Based on the background of achieving carbon peaking and carbon neutrality, the development and application of new high-power compressors, electric grid drilling RIGS and electric fracturing pump system provide new equipment support for the electric, green and intelligent development of shale gas fields in China. However, the harmonic pollution of shale gas grid becomes more serious due to the converter and frequency conversion device in the system, which easily causes harmonic resonance problem. Therefore, the harmonic resonance of shale gas grid is comprehensively analyzed and treated. Firstly, the working mechanism of compressor, electric drilling RIGS of the harmonic impedance model of electric fracturing pump system is established. Secondly, the main research methods of harmonic resonance analysis are introduced, and the basic principle of modal analysis is explained. Modal analysis method was used to analyze. Finally, harmonic resonance is suppressed. The results show that there may be multiple resonant frequency points in the distribution network changes, but these changes are relatively clear; if the original resonant frequency point of the resonant loop does not exist, the resonant frequency point disappears. The optimal configuration strategy of passive filter can effectively suppress harmonic resonance of distribution network in shale gas field.

Study on Suppression of Combustion Instability using Quarter Wavelength Tube

The passive suppression of combustion instability by quarter wavelength tube was hereby studied to absorb the oscillation pressure with large amplitudes caused by combustion instability. The suppression effects of quarter wavelength tube on combustion instability were systematically analyzed by combining the acoustic numerical simulation and the experimental research methods. Firstly, the influence of quarter wavelength tube on the acoustic characteristics of the system was analyzed using acoustic numerical simulation; and then, the acoustic absorption characteristics to external acoustic disturbance and the suppression effects on the self-excited combustion instability were experimentally studied. The results show that the quarter wavelength tube can effectively absorb the acoustic pressure when the dominant frequency of acoustic pressure is close to the resonance frequency of the system, and can effectively suppress the combustion instability under acoustic resonance. However, given that the quarter wavelength tube adds adjoint dominant frequencies after eliminating the original resonant frequency of the system, and the combustion instability is stabilized on the adjoint dominant frequencies, combustion instability suppression is different from noise suppression. In addition, the diameter of wavelength tube exercises obvious effects on the above characteristics. All these make it necessary to determine the best parameters and the maximum suppression efficiency by combining numerical simulation and experiments. The research results of this paper provide theoretical and technical supports for the suppression of combustion instability by the quarter wavelength tube.

Application of Heat-Enhancement for Improving the Sensitivity of Quartz Crystal Microbalance.

The use of quartz crystal microbalance in trace mass detection is restricted by unsatisfactory sensitivity, especially in damping media, due to the worsening of the quality factor of the damping resonator. The enhancement of the sensor performance could be realized by increasing the innate resonant frequency of quartz oscillators. Herein, increased working temperature of QCM systems was proved to bring an enhancement of the original resonant frequency. In addition, the measurement of ion osmotic pressure, single layer formation and single nucleotide polymorphism (SNP) at different temperatures demonstrated that an increased working temperature could enhance the sensitivity and accuracy, suggesting a potential application in a series of trace detections.

Enhancement of robustness to frequency detuning with wireless power transfer based on Van der Pol resonance

AbstractIn near‐field energy transmission, wireless power transfer based on magnetic coupling resonance is preferred. For efficient power transfer, the quality factor of magnetic coupling resonance wireless power transfer (MCR‐WPT) system should be kept at a high value, which makes the system sensitive to frequency detuning. Different from conventional approaches dealing with the problem in linear MCR‐WPT system, this paper proposes a novel MCR‐WPT system, which is based on Van der Pol nonlinear resonant circuit to address the problem of frequency detuning. A nonlinear resistor is introduced, and the nonlinear Van der Pol MCR‐WPT system is established. Based on the mathematical model and the theoretical analysis, it is found that the frequency band is broadened. To validate the performance of the proposed system, extensive simulation and experimental work are conducted. Unlike the traditional linear system, which only peaks at the resonant frequency, the results show that the output of the proposed system is still high within a certain frequency band when the operating frequency deviates from the original resonant frequency. The impact of frequency detuning caused by variation of capacitance is also studied. It can be concluded that the proposed MCR‐WPT system is effective in coping with the frequency detuning.

Experimental Research on Reducing Flow-Induced Cavity Resonance with a Narrowband Active Noise Control System

In this paper, active control of flow-induced cavity resonance noise is addressed. A hybrid numerical method is presented to predict the resonance frequency and, instead of traditional active flow control, a narrowband active noise control system is utilized to suppress the resonance. A duct system is built up at low Mach numbers and experiments are carried out to validate the proposed methods. The results have shown that the resonance frequency could be predicted with 1.5% errors and the flow-induced narrowband noise could be effectively suppressed at both the fundamental frequency and its first harmonic. More than 10 dB global attenuations could be achieved for the fundamental resonance frequency without noise enhancements at other frequencies. Further, it was also found that the optimal reference frequency of the narrowband active noise control system could be largely biased from the original resonance frequency, which indicates a nonlinear mechanism of the control system.

Spectral stability of bound state in the continuum resonances due to thermal effect and the application as efficient thermo-optic modulators

The phenomenon of bound state in the continuum (BIC) has raised ever-increasing research interest as a new means of manipulating light–matter interactions. The ultra-high quality factors associated with BIC resonances also make them very vulnerable to any environmental turbulence. For example, very weak changes of the refractive index may lead to large spectral shift. In this work, we numerically investigate the spectral stability of the quasi-BIC resonances due to temperature changes supported by all-dielectric optical nanoantennas in the form of slotted silicon disk array. We find that due to the extremely-high quality factor of the quasi-BIC mode, the resonance is very sensitive to ambient temperatures with a wavelength shift rate around 0.077 nm/K, resulting from the thermo-optic effect of the constituent materials. This effect of thermal tunability can nevertheless be utilized to achieve an efficient thermo-optic modulator and we demonstrate that the transmittance at the original resonance frequency will change from 0 to 1 when the temperature increases by only 5 Kelvin, using an experimentally obtained thermo-optic coefficient of silicon and fused silica as 1.8 × 10−4/K and 8.5 × 10−6/K respectively.

Frequency response of Quartz Crystal Microbalance under uniaxial force

Piezoelectric material produces electric fields due to a change of material dimension as an impact of external force/stress applied. One of the piezoelectric materials that widely used for a sensor is quartz crystals. Cutting crystal at its AT-Cut angle causes this material to have piezoelectric properties. Phenomena that occur on quartz surfaces can be observed and expressed as changes in the resonance frequency of sensors. In this experiment, a continuous uniaxial force from 0 N to 10 N was applied to the surface of the quartz crystal microbalance (QCM). The result shows that the resonance frequency of the QCM depends on the applied force. The resonance frequency increases as the applied force is increased. When the applied force is gradually decreased, the resonance frequency is also decreased and back to its original resonance frequency when there is no applied force. The frequency change of the sensor was linearly depend on the applied uniaxial force to the sensor.

A Solution to Frequency Splitting in Magnetic Resonance Wireless Power Transfer Systems Using Double Sided Symmetric Capacitors

The technology of wireless power transfer using magnetic resonance coupling has become a subject of interest for researchers with the proliferation of mobile. The maximum efficiency is achieved at a specific gap between the resonators in the system. However, the resonance frequency splits as the gap declines or gets smaller. Different methods have been studied to improve this such as frequency tracking and impedance matching, including capacitive tuning. However, the system has to maintain the same working frequency to avoid moving out of the license exempt industrial, scientific, and medical (ISM) band; and the efficiency must be as large as possible. In this paper, a symmetric capacitance tuning method is presented to achieve these two conditions and solve the splitting problem. In the proposed method, the maximum efficiency at one of the splitting frequencies is moved to match the original resonance frequency. By comparison to other works, both simulation and experiment show considerable improvements for the proposed method over existing frequency tracking and impedance matching methods. The paper also presents a proposal to apply this method automatically which can achieve wireless charging for electronic applications with high efficiency and through variable distance.

High-bandwidth nanopositioning via active control of system resonance

Typically, the achievable positioning bandwidth for piezo-actuated nanopositioners is severely limited by the first, lightly-damped resonance. To overcome this issue, a variety of open- and closed-loop control techniques that commonly combine damping and tracking actions, have been reported in literature. However, in almost all these cases, the achievable closed-loop bandwidth is still limited by the original open-loop resonant frequency of the respective positioning axis. Shifting this resonance to a higher frequency would undoubtedly result in a wider bandwidth. However, such a shift typically entails a major mechanical redesign of the nanopositioner. The integral resonant control (IRC) has been reported earlier to demonstrate the significant performance enhancement, robustness to parameter uncertainty, guaranteed stability and design flexibility it affords. To further exploit the IRC scheme’s capabilities, this paper presents a method of actively shifting the resonant frequency of a nanopositioner’s axis, thereby delivering a wider closed-loop positioning bandwidth when controlled with the IRC scheme. The IRC damping control is augmented with a standard integral tracking controller to improve positioning accuracy. And both damping and tracking control parameters are analytically optimized to result in a Butterworth Filter mimicking pole-placement—maximally flat passband response. Experiments are conducted on a nanopositioner’s axis with an open-loop resonance at 508 Hz. It is shown that by employing the active resonance shifting, the closed-loop positioning bandwidth is increased from 73 to 576 Hz. Consequently, the root-mean-square tracking errors for a 100 Hz triangular trajectory are reduced by 93%.

Dual-Band Microstrip Antenna Based on Polarization Conversion Metasurface Structure

A dual-band microstrip patch antenna based on polarization conversion metasurface structure is designed. By etching the complementary split ring resonator (CSRR) on the ground plane, a new resonance frequency is generated. The proposed antenna is obtained through optimizing the structural parameters of CSRR. Compared with the antenna without CSRR, the return loss of the proposed antenna increases by about 40% in the original resonance frequency. The measured results demonstrate good agreement with the simulated ones, verifying the reliability of the antenna. This work provides a way to the design of multi-band antenna.

Investigation into effect of coupled resonance phenomenon towards sensitivity enhancement of SAW conductivity sensors integrated with ZnO nanorods

In this work, FEM simulation was used to investigate the sensitivity of a one-port surface acoustic wave (SAW) resonator sensor to changes in electrical conductivity of the sensing medium composed of ZnO nanorods offering elastic loading on the surface of the resonator. A system of coupled resonators was formed when the height of the ZnO nanorods attached to the surface of the resonator was adjusted such that the resonant frequency of the nanorod approached the original resonant frequency of the SAW resonator. It was observed that the use of ZnO nanorods of resonant dimensions as sensing medium could enhance the sensitivity of the composite SAW sensor to changes in electrical conductivity of the sensing medium by up to 79 times. The comparatively higher sensitivity of the SAW conductivity sensor utilizing ZnO nanorods at resonant dimensions as sensing medium was attributed to the fact that the system of coupled resonators thus formed operates at a state of high sensitivity to changes induced in piezoelectric stiffening of the substrate during SAW propagation. The observations from FEM simulation conducted in the present work suggests strong prospects for the use of coupled resonance phenomenon at nanoscale for enhancing the sensitivity of conductivity-based SAW gas sensors and UV detectors employing 1-D ZnO nanostructures as sensing medium.

Cross Interference Minimization and Simultaneous Wireless Power Transfer to Multiple Frequency Loads Using Frequency Bifurcation Approach

Simultaneous power distribution to multiple loads using a single source in the wireless power transfer (WPT) system is a challenging issue due to cross-coupling between the load coils, which reduces the power transfer efficiency. In a resonant WPT system, when two or more coils operated under over coupled condition, the original operating resonant frequency gets bifurcated, and thereby reduction in the power transfer efficiency. Different techniques are investigated in the literature to mitigate the frequency bifurcation phenomena in the resonant WPT system. However, the utilization of frequency bifurcation approach for the simultaneous power transfer to multiple loads is not addressed. This paper proposes a simultaneous power transfer approach using frequency bifurcation for the multiple load system designed with different operating frequency. Mathematical, simulation, and experimental studies performed for dual, triple, and four coil WPT systems with multiple loads. In addition, an automatic power flow control method is implemented to estimate the load current from the source, which helps to select a new set of load coils to be charged. The experimental results confirm the proposed power transfer, helps to attain higher power transfer efficiency of 39.34%, 49.31%, 68.22% and cross interference of −31.2 dBV, −36.2 dBV, −41.2 dBV for dual, triple, and four coil WPT system, respectively.

Design of a compact dense dielectric patch antenna based on half‐cut technique

In this article, a half-cut rectangular dense dielectric patch (DDP) with one grounded side plane is theoretically investigated for designing a compact low-profile antenna. According to the properties and the E-field distribution of the dominant TM101 mode, the half-wavelength (λ/2) DDP can be bisected by effectively shorting the center plane to the ground, resulting in a miniaturized half-cut λ/4 DDP. The size of the DDP is effectively reduced by 50% while maintaining the original resonant frequency of the dominant TM101 mode. The half-cut λ/4 DDP can be well excited through aperture coupling for antenna design. The design procedure of the proposed antenna is given in detail. For demonstration, an antenna prototype centered at 4.15 GHz is implemented and measured. The simulated and measured results are given, showing good agreement.

Synchronized time-coupling theory of resonant mode splitting phenomena in a superconducting photonic crystal at terahertz

Resonant mode splitting phenomenon can be observed in the terahertz transmission spectrum of a finite superconducting photonic crystal (SD)NS, where S and D denote a superconducting layer and a dielectric layer, respectively. In this structure, each D-layer in (SD)NS constitutes a Fabry-Perot cavity. The original single resonant mode at N = 1 can then be split into N resonant modes for N > 1 due to the time-coupling effect coming from N cavities. Within the framework of the coupled mode theory, we successfully employ synchronized time-coupling theory to analytically explain the number of split resonant peaks, the resonant frequencies, and the frequency intervals between peaks. Additionally, it is found that the coupling coefficient is an increasing function of the original resonant frequency, which, in turn, indicates that the split frequencies and interval can be tuned by the thickness of layer D. Application of this synchronized time-coupling theory to elucidate similar splitting phenomena in plasma photonic crystals and metamaterial photonic crystals is also discussed.

Frequency Splitting-Based Wireless Power Transfer and Simultaneous Propulsion Generation to Multiple Micro-Robots

Multiple microrobots are needed in biomedical applications to perform time-bound complex clinical practices. Simultaneous wireless power transfer (WPT) and propulsion generation helps the designer to miniaturize the size and capable of executing multitasking operation. However, the selective power and force transfer to multiple devices is challenging and requires multiple frequency magnetic fields at the transmitter (Tx). This paper proposes a new approach of simultaneous independent wireless power and force generation using frequency splitting phenomena present in magnetic resonance. In the proposed approach, three coils at the Tx side is operated under over coupled (OC) mode, which produces three different split frequencies. The split frequency at the Tx side is utilized for the simultaneous independent power and force transfer to three different micro-robots and the number of micro-robots can be increased by operating the Tx side coil at different OC region. In addition, the split frequency of three coil WPT circuit comprises of the original resonant frequency irrespective of variation in coupling between the coils. This feature can be applied for the design of leader–follower control approach to the multiple micro-robots environments. The mathematical, simulations, and experimental analysis of power transfer and force generation at frequency splitting are performed for the proposed system with five load coils (considered as micro-robots).

Effect of Polypropylene Fibers on Self-Healing and Dynamic Modulus of Elasticity Recovery of Fiber Reinforced Concrete

This study aims to evaluate self-healing properties and recovered dynamic moduli of engineered polypropylene fiber reinforced concrete using non-destructive resonant frequency testing. Two types of polypropylene fibers (0.3% micro and 0.6% macro) and two curing conditions have been investigated: Water curing (at ~25 Celsius) and air curing. The Impact Resonance Method (IRM) has been conducted in both transverse and longitudinal modes on concrete cylinders prior/post crack induction and post healing of cracks. Specimens were pre-cracked at 14 days, obtaining values of crack width in the range of 0.10–0.50 mm. Addition of polypropylene fibers improved the dynamic response of concrete post-cracking by maintaining a fraction of the original resonant frequency and elastic properties. Macro fibers showed better improvement in crack bridging while micro fiber showed a significant recovery of the elastic properties. The results also indicated that air-cured Polypropylene Fiber Reinforced Concrete (PFRC) cylinders produced ~300 Hz lower resonant frequencies when compared to water-cured cylinders. The analyses showed that those specimens with micro fibers exhibited a higher recovery of dynamic elastic moduli.

High-efficiency resonant coupled wireless power transfer via tunable impedance matching

ABSTRACTFor magnetic resonant coupled wireless power transfer (WPT), the axial movement of near-field coupled coils adversely degrades the power transfer efficiency (PTE) of the system and often creates sub-resonance. This paper presents a tunable impedance matching technique based on optimum coupling tuning to enhance the efficiency of resonant coupled WPT system. The optimum power transfer model is analysed from equivalent circuit model via reflected load principle, and the adequate matching are achieved through the optimum tuning of coupling coefficients at both the transmitting and receiving end of the system. Both simulations and experiments are performed to evaluate the theoretical model of the proposed matching technique, and results in a PTE over 80% at close coil proximity without shifting the original resonant frequency. Compared to the fixed coupled WPT, the extracted efficiency shows 15.1% and 19.9% improvements at the centre-to-centre misalignment of 10 and 70 cm, respectively. Applying this technique, the extracted S21 parameter shows more than 10 dB improvements at both strong and weak couplings. Through the developed model, the optimum coupling tuning also significantly improves the performance over matching techniques using frequency tracking and tunable matching circuits.

Design of dual-band coil for wireless power transfer system via magnetic resonant coupling

For wireless power transfer (WPT) systems, communication between the two terminals of power transfer system is also an important problem to be solved. This paper proposes a design method of multi-turn dual-band coil for implementing synchronous transfer of power and data in WPT system with one set of WPT coils. An extra compensation circuit is inserted into the multi-turn spiral coil, so the new coil has two resonant frequencies that lie on both sides of the original resonant frequency of the multi-turn coil. Just one set of dual-band coils is used to provide the data and power transfer via two different resonant frequencies, so the undesirable interference in multi-coil WPT system is avoided. The equivalent circuit model is built to analyze the characteristic of the dual-band WPT system. The data pickup circuit is analyzed and designed for the receiver of WPT system. Finally, a dual-band WPT prototype with data pickup circuit is built to demonstrate the effectiveness of the proposed dual-band WPT system.