Order Resonant Frequencies Research Articles

Design of Dual-Band Bandpass Filter With High Isolation and Wide Stopband

A simple and effective method to design a dual-band bandpass filter with high isolation and wide stopband is presented and validated using symmetric open-circuited stub-loaded resonators. By adjusting the electric length and the ratio of characteristic admittance of the resonators, the first two resonant frequencies are identical, but the higher order resonant frequencies dispersed in the upper stopband to extent the bandwidth of stopband. Two transmission zeros are introduced to obtain high isolation and selectivity between the two passbands by placing them in the appropriate position. Proper feeding position is selected to further improve the attenuation of stopband. The measured results highly agree with the simulated one. Measured results demonstrate the isolation level of 40 dB, attenuation of larger than 28 dB, and a wide stopband.

A Systematic Method for Developing Harmonic Cantilevers for Atomic Force Microscopy

This paper proposes a method for developing harmonic cantilevers for tapping mode atomic force microscopy (AFM). The natural frequencies of an AFM cantilever are tuned by inserting gridiron holes with specific sizes and locations, such that the higher order resonance frequencies can be assigned to be integer harmonics generated by the nonlinear tip–sample interaction force. The cantilever is modeled using the vibration theory of the Timoshenko beam with a nonuniform cross section. The designed cantilever is fabricated by modifying a commercial cantilever through focused ion beam (FIB) milling. The resonant frequencies of the designed cantilever are verified using a commercial AFM.

A novel frequency tuned wireless actuator with snake-like motion

In this work, we propose a novel wireless actuator which is composed of magnetostrictive material/copper bi-layer film. The actuator can be controlled to move like a snake bi-directionally along a pipe by tuning the frequency of external magnetic field near its first order resonant frequency. The governing equation for the actuator is established and the vibration mode shape function is derived. Theoretical analysis shows that motion of the actuator is achieved by asymmetric vibration mode shape, specific vibration bending deformation, and effective net total impacting force. The simulation and experimental results well confirm the theoretical analysis. This work provides contribution to the development of wireless micro robots and autonomous magnetostrictive sensors.

Tunable and long-range energy transfer efficiency through a graphene nanodisk

In this paper, we present a theoretical investigation of the energy transfer efficiency between a pair of quantum emitters placed in proximity to a conducting graphene nanodisk. The energy transfer efficiency quantifies the contribution of the energy transfer process to the relaxation of the donor quantum system, as compared to the spontaneous emission rate of the donor in the absence of the acceptor. We use in our calculations the Green's tensor formalism in the electrostatic limit. This approximation works very well for the nanodisks considered here, for which the radius is much smaller than the emission wavelength of the donor. The approximate analytical solutions obtained are used to investigate the decay rate of a single quantum emitter and the energy transfer rate between quantum emitters in the vicinity of the graphene nanodisk. We find that these rates are enhanced several orders of magnitude compared with their free-space values. We determine the resonance frequencies of the spontaneous emission rate of a single quantum emitter to a graphene nanodisk, and the energy transfer rate between a pair of quantum emitters in proximity to a graphene nanodisk. We identify the surface modes which give the largest contributions to the energy transfer function. We connect the resonance frequency values and their surface plasmon wave numbers, which depend on the radius of the graphene nanodisk, with the dispersion relation of an infinite graphene monolayer at the same chemical potential. Analyzing the distance dependence of these rates, we are able to fit the full numerical results with a simple analytical expression which depends only on the geometrical characteristics of the graphene nanodisk, i.e., its radius. We show that the interaction distance depends on the transition dipole moment orientation and the different order resonance frequencies. The interaction distance between a pair of quantum emitters increases from a free-space value of $20\phantom{\rule{0.28em}{0ex}}\text{nm}$ to reach values of 120 nm in the presence of a graphene nanodisk.

Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy.

In multifrequency atomic force microscopy (AFM), probe's characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude's sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

Synergistic use of smart materials for vibration-based energy harvesting

Vibration-based energy harvesting is an approach where available mechanical vibration energy is converted into electrical energy that can be employed for different purposes. This paper deals with the synergistic use of smart materials for energy harvesting purposes. In essence, piezoelectric and shape memory alloys are combined to build an energy harvesting system. The combined effect of these materials can increase the system performance and reduce some limitations. The possibility to control the mechanical stiffness under vibration by a shape memory alloy (SMA) element can provide the ability to tune resonant frequencies in order to increase the output power. The analysis is developed considering a one-degree of freedom mechanical system where the restitution force is provided by an SMA element. The electro-mechanical coupling is provided by a piezoelectric element. Linear piezoelectric constitutive equation is employed together with the Brinson’s model for SMA element. Numerical simulations are carried out showing different responses of the system indicating that the inclusion of the SMA element can be used to extend the operational range of the system.

An Inductive Power Transfer System With a High-Q Resonant Tank for Mobile Device Charging

Inductive power transfer (IPT), which employs the principle of electromagnetic induction, is widely applied to wireless charging applications. The efficiency of an IPT system is highly dependent on the quality factor (Q) of the power resonant tank. In this paper, a novel design on the structure of the resonant coil is used in the resonant tank to achieve a significantly high Q above 1000 for the IPT system. Compensating capacitors are used in both primary and secondary circuits to align the resonant frequencies in order for the system resonant status to be maintained by a frequency tracking circuit. The experimental results show that with a primary coil Q of 1200, the proposed IPT system allows power to be transferred at a maximum air gap distance to coil diameter ratio of 1.46 for a highest efficiency of 87% at the resonant frequency of 106 kHz.

Structure Optimization of the Aluminum Alloy Frames of Flight Simulator

Frames are the main components of the flight motion simulator, which are the support for each shaft system, at the same time the rotating load for the external shaft, so the stiffness and dynamic characteristics of the frames in a large extent determines the final accuracy and dynamic performance of the flight motion simulator. For the cast aluminum alloy ZL114A frames of a 3-DOF flight motion simulator, using finite element analysis method, the dynamic characteristics are calculated and analyzed, and then the each order resonance frequency and mode of vibration are obtained. By using of the modal synthesis method and optimization algorithms, the structural dynamics of frames are designed optimally, so as to further reducing the moment of inertia, and improving the stiffness and dynamic characteristics of frames. This method has provided important reference for the reasonable design of the frame structure, and definitively established the foundation to further study the triaxial coupling dynamic characteristics and system mechanical optimization for the flight motion simulator.

Design of Microstrip Triplexer Using Common Dual-Mode Resonator with Multi-Spurious Mode Suppression for Multiband Applications

A triplexer is an important component for channel separation in microwave front-end systems. This paper proposes a triplexers designed with common dual mode resonator sections have been proposed. By exploiting the variable frequency response of the stepped-impedance resonator, resonators can be shared by the three filter channels of the desired triplexer if their fundamental and the first spurious resonant frequency are properly assigned. Triplexer design method for suppressing spurious responses in the stopband by choosing the constitutive resonators with the same fundamental frequency, but staggered higher order resonant frequencies. The design concept is demonstrated by three of third order parallel-coupled bandpass filters. The bandpass filter is composed of three different stepped impedance resonators for which a general design guideline had been provided in order have the same fundamental frequency and different spurious frequencies. The measured results are in good agreement with the simulated predictions, whereby the spurious responses in the upper stopband can be suppressed below-25dB up to 14 GHz, which can be quite useful for multiband and multiservice applications in future wireless communication systems.

A Study on the Measurement and Analysis of Whirling Vibration Behavior of Marine Propulsion Shafting System using Gap-sensors

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational rpm range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering from operating rpm up to target rpm, however, the range is un-measurable generally. In order to resolve the measurement issue, this study shows the measuring method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration.

A variable-width harmonic probe for multifrequency atomic force microscopy

In multifrequency atomic force microscopy (AFM) to simultaneously measure topography and material properties of specimens, it is highly desirable that the higher order resonance frequencies of the cantilever probe are assigned to be integer harmonics of the excitation frequency. The harmonic resonances are essential for significant enhancement of the probe's response at the specified harmonic frequencies. In this letter, a structural optimization technique is employed to design cantilever probes so that the ratios between one or more higher order resonance frequencies and the fundamental natural frequency are ensured to be equal to specified integers and, in the meantime, that the fundamental natural frequency is maximized. Width profile of the cantilever probe is the design variable in optimization. Thereafter, the probes were prepared by modifying a commercial probe through the focused ion beam (FIB) milling. The resonance frequencies of the FIB fabricated probes were measured with an AFM. Results of the measurement show that the optimal design of probe is as effective as design prediction.

Electron densities inferred from plasma wave spectra obtained by the Waves instrument on Van Allen Probes.

The twin Van Allen Probe spacecraft, launched in August 2012, carry identical scientific payloads. The Electric and Magnetic Field Instrument Suite and Integrated Science suite includes a plasma wave instrument (Waves) that measures three magnetic and three electric components of plasma waves in the frequency range of 10 Hz to 12 kHz using triaxial search coils and the Electric Fields and Waves triaxial electric field sensors. The Waves instrument also measures a single electric field component of waves in the frequency range of 10 to 500 kHz. A primary objective of the higher-frequency measurements is the determination of the electron density ne at the spacecraft, primarily inferred from the upper hybrid resonance frequency fuh. Considerable work has gone into developing a process and tools for identifying and digitizing the upper hybrid resonance frequency in order to infer the electron density as an essential parameter for interpreting not only the plasma wave data from the mission but also as input to various magnetospheric models. Good progress has been made in developing algorithms to identify fuh and create a data set of electron densities. However, it is often difficult to interpret the plasma wave spectra during active times to identify fuh and accurately determine ne. In some cases, there is no clear signature of the upper hybrid band, and the low-frequency cutoff of the continuum radiation is used. We describe the expected accuracy of ne and issues in the interpretation of the electrostatic wave spectrum.

High Power Electromechanical Characterization of Piezoceramics and Low Frequency Ultrasound Transducers by Using Algorithm for Tracking Changes in Resonant Frequency and Electrical Impedance

Electromechanical and acoustical characterization of PZT piezoceramic elements and high-power ultrasound transducers has been done around resonance frequencies in order to determine the features of the models that describe the considered devices, both as equivalent circuits and as nonlinear oscillators. Several measurement methods have been compared, including the frequency-sweeping method with constant excitation voltage, the magnitude-sweeping method at a constant excitation frequency and the method that uses impulse excitation. The parameters that describe the losses in a coupled nonlinear electro-mechanical-acoustical system greatly depend on the type of excitation and its level. A novel algorithm is tested, designed for tracking the changes of the series resonance frequency and impedance magnitude and phase with the excitation level. It enables a more precise determination of the resonance frequency and impedance changes over different levels of excitation, which is especially important in high-power resonant applications. The characterization based on frequency sweeping at different excitation levels is influenced by changing electrical parameters (current, voltage, power) due to different complex loading of the excitation amplifier and the changes of thermodynamic conditions. The characterization of transducers in loaded condition through frequency sweeping at higher signal levels gives no results when cavitation in front of the horn appears, because the impedance magnitude changes at higher excitation voltages. Using the tracking algorithm, the impedance magnitude at resonance frequency has been determined in a range of different excitation levels up to 35 VRMS. Before the onset of nonlinear effects such as cavitation or acoustic streaming, the impedance magnitude increases due to viscosity effects.

Omnidirectional piezo-optical ring sensor for enhanced guided wave structural health monitoring

This paper presents a novel method for the detection of ultrasonic waves from acoustic emission events using piezoelectric wafer ac3tive sensors (PWAS) and optical fiber Bragg grating (FBG) sensing combined with mechanical resonance amplification principles. The method is best suited for detecting the out-of-plane motion of the AE wave with preference for a certain frequency that can be adjusted by design. Several issues are discussed: (a) study the mode shapes of the sensors under different resonance frequencies in order to understand the behavior of the ring in a frequency band of interest; (b) comparison of analytical results and mode shapes with FEM predictions; (c) choice of the final piezo-optical ring sensor shape; (d) testing of the piezo-optical ring sensor prototype; (e) discussion of the ring-sensor test results in comparison with conventional results from PWAS and FBG sensors mounted directly on the test structure. The paper ends with summary, conclusions, and suggestions for further work.

Design and implementation of weaving‐type pad for contactless EV inductive charging system

The purpose of this study is to develop a new weaving-type pad for electric vehicles (EV) contactless inductive charging system. This proposed charging pad which consists of a weaving-type coil is fabricated to obtain a uniform mutual inductance profile over the charging surface and to solve the problem of present inductive coupled structure in which the EV has to be placed exactly on a specific place. Apart from weaving-type pad, type E core and two overlapping coils are utilised as a secondary pickup to guide and to pick more magnetic flux. The analysis and simulation of magnetic characteristic for comparing the proposed weaving-type pad to simple shape pad are performed by finite-element-analysis (FEA) software. Phase locked loop circuit is utilised to match the operating frequency and resonant frequency in order to solve the loading effect problem caused by impedance variation during the battery charging procedure. To validate the concept and system design, a laboratory scale test system with weaving-type pad for EV contactless inductive charging is built and tested. The coupling efficiency is found to be 66% for an air gap of 9 cm between the weaving-type charging pad and pickup when a 2 Ah lithium iron phosphate battery is charged.

Novel Trapezoidal-Loop Piezoelectric Energy Harvester

In recent years, piezoelectric energy harvester which can replace the traditional battery supply has become a hot topic in global research field of microelectronic devices. Characteristics of a trapezoidal-loop piezoelectric energy harvester (TLPEH) were analyzed through finite-element analysis. The output voltage density is 4.251V/cm2 when 0.1N force is applied to the free end of ten-arm energy harvester. Comparisons of the resonant frequencies and output voltages were made. The first order resonant frequency could reach 15Hz by increasing the number of arms. Meanwhile, the output voltage is improved greatly when excited at first-order resonant frequencies. The trapezoidal-loop structure of TLPEH could enhance frequency response, which means scavenging energy more efficiently in vibration environment. The TLPEH mentioned here might be useful for the future structure design of piezoelectric energy harvester with low resonance frequency.

Novel Low-Frequency Rectangular-Loop Piezoelectric Energy Harvester

The ambient energy harvesting based on piezoelectric has become an important subject in recent research publications. A new rectangular-loop piezoelectric energy harvester(RLPEH) is proposed. The characteristic is analyzed by the finite element analysis (FEA) which includes the static analysis, modal analysis and harmonic response analysis. The analysis results show that the RLPEH could reduce the resonant frequency and improve the output voltage. The three order resonant frequency is 18.6Hz, 40.8Hz and 85.4Hz. The output voltage is 42V under 3m/s2 of acceleration and the effective bandwidth is 18.7Hz with output voltage above 10V.

月基光学天文望远镜反射镜转台的设计

To implement the astronomical observation on the moon,the thermal analysis and structure design of a 2Dreflection mirror gimbal for the lunar based astronomy optical telescope were performed.The 2Drotary structure of reflection mirror was designed based on lightweighting method to reduce the load mass.Because an external rotor mechanism was used for the vertical shaft,the first order mode of the system along the emission direction was greatly improved.For a larger span in the horizontal shaft,a shaft system with one fixed end and another free end was adopted.Moreover,the clearance of deep groove ball bearings was designed rationally to eliminate the block of the rotary structure caused by temperature changes on the moon.In order to meet the high accuracy,the reflection mirror gimbal used a worm gear and a step motor to drive the gimbal and to control the machining in a strict technology.In addition,an optics switch was used to achieve high accuracy position and make the accuracy of gimbal be better than 60″。Experiments show that the first order resonant frequency of the system can reach 81 Hz along the rocket-firing track,the mechanism works well at-25℃to+60℃ without stuck phenomenon and its direction accuracy is less than 60″.These results demonstrate that the system is characterized by high accuracy,high reliability and light weight.

Finite element analysis of nonlinear wave resonance by multiple cylinders in vertical motions

The finite element method (FEM) is employed to analyse the resonant oscillations of the liquid confined within multiple or an array of floating bodies with fully nonlinear boundary conditions on the free surface and the body surface in two-dimensions. The velocity potentials at each time step are obtained through the FEM with 8-node quadratic shape functions. The finite element linear system is solved by the conjugate gradient (CG) method with a symmetric successive overelaxlation (SSOR) preconditioner. The waves at the open boundary are absorbed by the method of combination of the damping zone method and the Sommerfeld–Orlanski equation. Numerical examples are given by an array of floating wedge-shaped cylinders and rectangular cylinders. Results are provided for heaving motions and wave elevations, wave profiles and hydrodynamic forces are obtained. It is found the wave amplitude and the hydrodynamic force on a cylinder increase with their locations closer to the middle of the array at the first order resonant frequency and their second order component obtained by Fourier analysis becomes larger at the second order resonant frequency. Comparisons are also made in several cases with the results obtained from the second order solution in the time domain. The difference between the fully nonlinear result and the second order solution is discussed at both the first- and second-order resonant frequencies.

Structure Simulation Analysis of Piezoelectric Energy Harvesting Device

A low frequency energy harvesting structure was studied, describing the process of its manufacture. The natural frequency was obtained by modal analysis of the structure. It obtained the relationship between the magnitudes of the voltage generated from the piezoelectric energy harvesting device and the size parameters of structure, so that the energy harvesting structure can operate at the resonant frequency in order to obtain the maximum energy.