Order Resonant Frequencies Research Articles

Planar dual-band bandpass filter with regular harmonic suppression

Abstract This paper presents a dual-band bandpass filter with regular harmonic suppression. The proposed third-order filter consists of two microstrip stepped impedance resonators and single substrate integrated waveguide resonator. The mismatches in their higher order resonant frequencies are utilized to suppress the regular harmonics. The passbands are centered at f1 = 2.4 GHz and f2 = 3.5 GHz with fractional bandwidths of 5% and 7.5%, respectively. The measured midband insertion and return losses are better than 2.55 and 14.5 dB for the first, whereas for the second band, they are better than 1.95 and 14 dB. The filter offers at least 33 dB suppression of first three higher order regular harmonics of f1 and f2.

Holistically Nested Edge Detection and particle filtering for subtle vibration extraction

Extracting and analyzing subtle motion via optical sensing techniques is becoming a more important research area within the vibration community. Computer vision approaches and machine learning architecture have been adopted to contest the complexity concerning hand instrumentation of sensors. Pre-treatment using a stochastic pattern for optical analysis or traditional wired sensing is not always permitted for large structures. In this work, Holistically Nested Edge Detection (HED) is utilized to highlight high-spatial-frequency content features in images for structural dynamic analysis. Following the accentuation of edge features, phase-based motion magnification (PMM) is used to amplify motion that is not visible to the naked eye. This permits the band-passing of higher order resonant frequencies for structural dynamic evaluation. Implementation of two-dimensional particle filtering (PF) is utilized to track the accentuated edge features in the presence of ghosting artifacts that appear post magnification. Within this work, compared to traditional edge-thresholding, the combination of HED and PF (HED-PF) is more proficient to handle noise and ultimately improves magnified image quality and modal parameter extraction. Uncertainties related to using PF for vibration measurement are analytically presented to provide guidance on the behavior of the algorithm. To demonstrate the effectiveness of HED-PF, experimental modal testing takes place on both a tier-structure and cantilever beam to demonstrate the approaches’ capability in handling varying sorts of excitation. Finally, introduction of background occlusions and non-ideal lighting scenarios are used to test the limitations of the approach. Ultimately, this will highlight HED-PF’s robust tracking capabilities compared to the current state of the art.

Pseudo-resonance phenomenon of valveless piezoelectric pump

Volumetric piezoelectric pumps are widely used in the field of microfluidic drive due to their simple structure, flexible design, and absence of magnetic interference. As driven by the volume change of the pump chamber, the majority of this kind of pumps work under the first order resonance frequency, where the volume change is the largest. However, the experimental parts or data of many studies reflect a phenomenon that a flow rate peak exists in the non-resonance frequency range. This phenomenon has not been studied or explained in depth, and goes against conventional vibration theories. In this study, we define this phenomenon as the pseudo-resonance phenomenon, and the corresponding flow rate peak is named as the pseudo-resonance flow rate peak. First, a non-single-channel composite tapered tube valveless piezoelectric pump (NCTVP) was designed, which reproduced the pseudo-resonance phenomenon reported in the literature. Through displacement measurement experiments, it was demonstrated that the vibration mode of the piezoelectric vibrator was B00 mode when the pseudo-resonance phenomenon occurred. Then, frequency sweeping experiments and flow field observation experiments were conducted, it can be obtained that the pseudo-resonance phenomenon is caused by the reaction force of the water to the piezoelectric vibrator, and the reaction force is generated by the impact of two streams. Finally, based on the experiment results, a theoretical model was established; it was deduced that the first order resonance flow rate peak was caused by the flow resistance difference between the forward and reverse flows of the tapered tubes in NCTVP, and that the pseudo-resonance flow rate peak was caused by the water hammer effect. By applying the pseudo-resonance phenomenon, another flow rate peak was obtained in the non-resonance frequency range without changing the mechanical structure, which can enable piezoelectric micro nano pump to obtain extra flow rate or pressure without changing the constraint boundary conditions.

Vibroacoustic Transfer Characteristics of Underwater Cylindrical Shells Containing Complex Internal Elastic Coupled Systems

Cylindrical shells containing complex elastic coupling systems are the main structural form of underwater vehicles. Therefore, in this paper, the vibroacoustic radiation problem of underwater cylindrical shells containing complex internal elastic coupling systems is studied. Firstly, the dynamics model of the complex elastic coupled system is established through the method of integrated conductivity. The sound pressure distribution law and the general magnitude relationship between the performance index of hydroacoustic radiation and vibration isolation are investigated through numerical simulation. A strategy of global sensitivity analysis and related parameter optimization is carried out, by applying the Sobol’ method to the dynamics model. It could be concluded that the main flap of sound pressure at low and medium frequencies appears in the direction of the excitation force or the perpendicular to the excitation force, the magnitudes correspondence between the vibration level drop—power flow—hydroacoustic radiation at low frequencies can be expressed as a relatively simple function, and the vibroacoustic transmission of the system at lower order resonance frequencies is dominated by the parameter configuration of the vibration isolation device, while at higher frequencies is more influenced by the modalities of the base structure. The transfer power flow and the level drop are used as objective functions to optimise the acoustic radiation index of the coupled system, with the best results obtained when the transfer power flow and the level drop are used together as objective functions.

Dynamic Behavior Analysis of LNG Tank Under Different Earthquake Loads

Liquefied natural gas (LNG) is widely used all over the world and is transported by different types of pressurized tanks, among which the most convenient transfer method is a type C pressurized cylindrical tank. Any damage or leak in the tank might pose a serious risk. As a result, it is critical to investigate both its static and dynamic features. This paper represents the computational analysis of how the tank will behave under different load cases and also under different earthquake ground motions. The static analysis has been done with different internal pressure stresses and ultimate bearing pressure stress has been recognized. The tank has been subjected to modal analysis to get various mode shape findings with resonant frequencies in order to satisfy the requirements for analyzing the tank under various earthquake ground motions. Transient analysis has been utilized to assess dynamic behavior. A concept of selecting different ground motions is presented in this paper. Site parameters have been split into four categories, and the four sites with the severest real ground motions have been selected for this study. The paper represents how the tank will deform under different earthquake motions based on its location and site categories.

Machine Learning Based Design of Pattern Reconfigurable Antenna

In this study, a Machine Learning (ML) is implemented to soft computation of the Reconfigurable Horn Bowtie Dumbbell (RHBD) antenna at operating frequency range from 26 GHz to 29.5 GHz for 5G applications. An adaptive learning rate approach is used to build a ML model on a 5-layer system utilizing a simulated database of 180 RHBD antennas. In the training stage of a hybrid method that combines the advantages of particle swarm optimization (PSO) with a modified version of the gravitational search algorithm (MGSA), the architecture frame and hyper-parameters of the ML model are optimized. A precise electromagnetic analysis platform is used to simulate 180 RHBD antennas with varying geometrical properties in terms of the resonant frequency in order to create the database for training and testing the model. The ML model is tested and validated using a fabricated RHBD antenna operating at 27.5 GHz. Then, three PIN diodes are placed in the gaps of the reflectors located at the back of the antenna, and by changing the state of these PIN diodes, it can be noticed that they have a significant and direct effect on the radiation pattern, as they are able to change the beamwidth from 10.7° to 156.2°. The suggested antenna makes it easier to create dynamic radiation patterns that may be utilized to reconfigure the coverage area as required in accordance with the spatial-temporal user and traffic variations in high mobility environments.

Arbitrary variable thickness annular piezoelectric ultrasonic transducer based on transfer matrix method

The variable thickness annular radial piezoelectric ultrasonic transducer can realize impedance transformation and energy concentration, has the advantages of large radiation area and full directivity, and is widely used in power ultrasound, underwater acoustic and other fields. Because solving complex variable thickness metal ring radial vibration wave equation is more difficult, in this paper, the radial vibration of metal rings with variable thickness is transformed into the superposition of the radial vibrations of N metal rings with equal thickness by using the transfer matrix method. The equivalent circuit diagram, the resonance frequency equation and the expression of the displacement amplification coefficient of the radial vibration of the metal thin ring with arbitrary thickness are obtained. The relationship between the displacement amplification coefficient and the geometric size of the cone, power function, exponential and catenary metal rings is analyzed. On this basis, the equivalent circuit and resonance frequency equation of radial vibration of piezoelectric ultrasonic transducer which is composed of a metal ring with variable thickness and a piezoelectric ring with equal thickness are derived. In order to verify the correctness of the theoretical results, the finite element software is used in simulation, and the numerical solutions of the first and second order resonance frequency and displacement amplification coefficients are in good agreement with the theoretical solutions. In this paper, the universal solution of radial vibration of metal ring with arbitrary variable thickness is given, which provides theoretical guidance for designing and optimizing the radial piezoelectric ultrasonic transducers.

Tuning the higher to lower order resonance frequency ratio and implementing the tunable THz MIMO/self-diplexing antenna

The frequency ratio of higher to lower order mode can be electronically tuned in a terahertz (THz) antenna with metallic radiator using a graphene loop. Antenna is designed with slotted metallic radiator to obtain the dual-band response with fundamental and second order transverse magnetic mode providing the directional and bi-directional radiation pattern in the lower and upper band, respectively. The insertion of graphene loop and varying its chemical potential (μc) provides two resonances until 0.4eV and four resonances for further greater values of μc. The desired impedance matching can be achieved at the frequencies of any two resonances at a time by selecting an appropriate value of μc. Antenna can operate with higher/lower order mode centred at frequency 3.77/3.02 THz and 4.39/2.86 THz for the values of μc as 0.9 and 0.3eV , respectively. The frequency ratio of higher to lower order mode can be tuned within the range of 1.22–1.59 with the variation in μc. Also, application of graphene loop confines the radiated power in a single direction at the frequency of higher order mode making the radiation pattern consistent. Antenna can be utilized in future THz wireless applications which require the utilization of adjacent channels with different frequencies in communication. Also, a two-port antenna is designed which can offer the tunable multi-input–multi-output (MIMO) and self-diplexing capability with pattern diversity. The MIMO parameters; envelope correlation coefficient (ECC) and diversity gain (DG) is evaluated and their values are found within acceptable limits as ECC<0.06 and DG>9.9 in the operating bands.

Research on the selection and layout of the cantilever sensor based on photoacoustic spectroscopy gas detection technology

Gas detection has become an indispensable part of the power equipment maintenance. Because of many advantages, cantilever enhanced photoacoustic(PA) spectroscopy was studied by many researchers. In this paper, with the help of Finite Element Method (FEM) simulations with the commercial software COMSOL, we have analyzed the distribution of the sound pressure inside the gas cell, in addition, we have analyzed the relationship between the Young’s modulus and size of the cantilever beam and its deformation, the relationship between the cantilever size and its eigen-frequencies were also obtained. Besides, we have performed the experiment of the deformation measurement. The results show that: for the gas cell, when it works at the first order resonance frequency, the maximum value of the sound pressure appears at the geometric center. For the main resonance cavity, with its length and radius increase, the first order resonance frequency of the gas cell decreases. Under the condition of ideal linear sound source, as the length and radius of the main resonance cavity changes, in the frequency domain, the sound pressure response curve changes, the maximum sound pressure corresponds the PA cell with 85 mm in length and 2 mm in radius. For the cantilever beam, with the increase of the Young’s modulus, the deformation decreases. The deformation is proportional to the fourth power of the length, whereas it is inversely proportional to the width and inversely proportional to the third power of the thickness. However, the experimental results showed that there may be a deviation in the vibration measurements by the vibration meter. As for the first order eigen-frequency, it is negatively correlated with the length and positively correlated with the thickness, but independent of the width. With the increase of the distance between the sound source and the cantilever beam, the deformation decreases.

Development of a novel two-DOF piezo-driven fast steering mirror with high stiffness and good decoupling characteristic

A novel two-DOF piezo-driven fast steering mirror (PFSM) with high stiffness and good decoupling characteristic was proposed. This PFSM could realize rotary motions around X-axis and Y-axis by differential push–pull structure with four piezoelectric stack actuators (PSAs) arranged in cross and orthogonal state, and its lateral stiffness was high enough to overcome the problem that PSA was easy to be destroyed by large lateral force. The PFSM was designed and its working principle was described in detail. The static model was established to analyze the stiffness characteristic of the structure and precisely predict the output angles. The finite element method (FEM) was performed to verify the effectiveness of the proposed structure and static model. A prototype of the PFSM was fabricated, and an experimental setup was established. The experiments showed that the proposed PFSM could achieve rotary motion ranges of 2.33 mrad around X-axis and 2.25 mrad around Y-axis under the voltage of 120 V, respectively. And the resolution was measured as high as 0.28 μrad with the voltage increment of 0.2 V. Furthermore, the first order resonance frequency was measured as 4578 Hz and a good decoupling characteristic was obtained, the coupling errors of both two axes were below 0.75%. The two-DOF PFSM could be applied to the laser communication and the adaptive optics system based on its merits of high stiffness, high resolution and good decoupling characteristic.

Determining material properties of components with complex shapes using Resonant Ultrasound Spectroscopy

In this paper, Resonance Ultrasound Spectroscopy (RUS) is used to invert the elastic properties of components with complex shapes from a limited selection of mode matched frequencies. RUS is based on the unique relationship between the vibrational resonance response (resonance frequencies and mode shapes) of a component and its set of material properties, geometry, and boundary conditions. The study is conducted on 3 nominally identical components that have geometric imperfections due to the manufacturing process. The study reveals that an accurate characterization of the shape is critical to the success of the RUS process. The RUS process presented in this paper also relies on matching measured and computed vibrational mode shapes, in addition to the resonance frequencies. This strategy enables using high-order modes with complex modal information, in a frequency range with high modal density where modal identification based on the resonance frequencies alone would be challenging. This approach contrasts with the traditional approach of matching a number of resonance frequencies in sequential order. With the proposed approach, the elastic constants for the three components are similar, consistent with values found in the literature, and lead to small error of the RUS inversion, despite variations in the shapes and the resulting changes in the resonance response of the components.

Miniature Electrodynamic Wireless Power Transmission Receiver Using a Micromachined Silicon Suspension

We present the design, modeling, fabrication, and experimental characterization of an electrodynamic wireless power transmission (EWPT) receiver for low-frequency (<; 1 kHz), near-field wireless power transmission. The device utilizes a bulk-micromachined silicon serpentine suspension, two NdFeB magnets and two precision-manufactured coils. The architecture of the transducer is designed to maximize the electrodynamic coupling coefficient while maintaining a low mechanical resonant frequency in order to maximize the power density for low-frequency wireless power transmission. An equivalent lumped-element circuit model is established to parameterize the system and to predict the output performance of the proposed system. A prototype device is fabricated, assembled and tested, and the results are compared with the model prediction. The 0.31 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> device generates 2.46 mW average power (7.9 mW·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> power density) at 4 cm distance from a transmitter coil operating at 821 Hz and safely within allowable human exposure limits. This data corresponds to a normalized power density of 21.9 mW·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ·mT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , which is 44% higher than similar reported devices. Based on these results, this device shows great suitability for wirelessly charging mobile, wearable and bio-implantable devices. [2020-0161]

Optimal design and experiment study of the double spherical rotor of the MSCSG.

The magnetically suspended control and sense gyroscope (MSCSG) integrates spacecraft attitude measurement and control function; this paper proposes a double spherical rotor (DSR) for MSCSG. The DSR realizes the five degrees of freedom (DOFs) full active control and full channel magnetic path decoupling by the following design: the spherical axial/radial reluctance magnetic bearings are adopted to control the 3DOFs translation of rotor in the range of double spherical envelope, Lorentz force magnetic bearing (LFMB) is used to precisely drive the 2DOFs universal deflection of rotor. The optimization model is established based on the structural mechanical analysis, taking the deviation between rotor centroid and shape center as the optimization objective, choosing the first order resonance frequency, maximum equivalent stress, rigid body displacement, polar moment of inertia and inertia ratio as constraints. Then the DSR is optimized and simulated by the finite element, the MSCSG principle prototype based on DSR is successfully developed, the online dynamic balance experiment and modal test of the DSR are conducted, where the vibration amount of the DSR decreases from 20 μm before the experiment to 0.14 μm after the experiment, which decreases by 99.3%, the first test modal is 2881 Hz which is 5% different from the finite element simulation value of 3034 Hz. The results show that the DSR has the good mechanical properties and magnetic circuit decoupling characteristics.

Experimental study on modal characteristics of flame tube in a can type combustor in aero-engine

The flame tube is a key component in the combustor of the gas turbine engine. It is important to understand the structure dynamic characteristics of the tube. The present paper used both FEM and experiment modal method to examine the vibrating modal characteristics of a flame tube in a can type combustor. Its first six orders' modal parameters such as frequency and mode were obtained, respectively. The calculated results show that the flame tube vibrates along x- and y-directions. The tangential vibration with several circumferential waves and few horizontal half waves was observed. The tube's lower order resonant frequencies vary from 145 to 600 Hz, and its higher order frequencies are about 1000 Hz. The first three orders' frequencies of the tube in experiment are lower by about 30% than those by FEM method, but the calculated last three orders' frequencies are consistent with the experimental ones.

Placement of multiple low order resonance frequencies due to rigid coupling of a rigid and small subsystem to a main system

Placement of multiple low order resonance frequencies due to rigid coupling of a rigid and small subsystem to a main system

Design of a High-Sensitivity Microstrip Patch Sensor Antenna Loaded with a Defected Ground Structure Based on a Complementary Split Ring Resonator.

A comparative study to determine the most highly sensitive resonant frequency among the first four resonant frequencies of a conventional patch antenna and defected ground structure (DGS)-loaded patch antennas using commonly used DGS geometries in the literature, such as a rectangular slit, single-ring complementary split ring resonators (CSRRs) with different split positions, and double-ring CSRRs (DR-CSRRs) with different locations below the patch, for relative permittivity measurement of planar materials was conducted. The sensitivity performance for placing the DGS on two different locations, a center and a radiating edge of the patch, was also compared. Finally, the effect of scaling down the patch size of the DGS-loaded patch antenna was investigated in order to enhance the sensitivities of the higher order resonant frequencies. It was found that the second resonant frequency of the DR-CSRR DGS-loaded patch antenna aligned on a radiating edge with a half scaled-down patch size shows the highest sensitivity when varying the relative permittivity of the material under test from 1 to 10. In order to validate the simulated performance of the proposed antenna, the conventional and the proposed patch antennas were fabricated on 0.76-mm-thick RF-35 substrate, and they were used to measure their sensitivity when several standard dielectric substrate samples with dielectric constants ranging from 2.17 to 10.2 were loaded. The measured sensitivity of the second resonant frequency for the proposed DGS-loaded patch antenna was 4.91 to 7.72 times higher than the first resonant frequency of the conventional patch antenna, and the measured performance is also slightly better compared to the patch antenna loaded with a meander-line slot on the patch.

Design of Mechanical Multi-Sensor for Contaminated Water Filter Applications

Effect of addition (salts, soil and bacteria) on piezoelectric detecting a signal of a specific liquid like water has been inspected here in the project. Identifying signals (piezoelectric) categorized and accomplished by usage of transducer that conducts a mechanical signal in the direction of the water liquid cell, and then the receptor collects the weakened indications. The quartz cell (contains water solution) embedded between the two piezo crystals and piezo crystals with silver (Ag) nanowire thin film prepared using hydrothermal method. It is clear that the formation of the yield is rope-similar and close to be uniform in width (60 ± 10 nm) whereas the extent is in a moderately wide range (from 0.2 to 4 μm) with an average at 2.5 μm. Four peaks can be recognized in XRD results, it is clear according to the ASTM cards that the film is polycrystalline at which (111), (200) and (220) silver (Ag) respectively. The range of functioning frequencies was (400 kHz - 40MHz), for all specimens, the measurement outcomes that involved reporting the first order resonance frequencies. The data presented shifting the resonance frequency to the higher order frequency for addititive cases (salts+soil+bacteria) of water.

Optimization of a mass matrix for properly assigning low order resonance frequencies by the addition of a rigid and small subsystem

Optimization of a mass matrix for properly assigning low order resonance frequencies by the addition of a rigid and small subsystem

Non-resonant Frequencies in Mobile Wireless 5G Communication Networks

New emerging technology 5G will require higher speed, power and capacity in data transmission than previous generation, in order to obtain a complete world-wireless communication without limitation. In this scenario, given that the achievement of 5G technology will lead to a drastic increase of effects of exposure to microwave radiation, a strategy to reduce the effects of exposure to electromagnetic fields is needed. In this regard, given that cellular functions of human beings depend closely on ions flux across cellular membrane, whose mechanism should have its natural resonant frequencies, we can hypothesize to plan new emerging wireless technology 5G at frequencies far from these resonant frequencies in order to minimize the effects of exposure to extremely high frequency electromagnetic fields, inducing a significant decreasing of harmful effects on human health. We have named these frequencies “non-resonant frequencies”.

Piezoelectric Electro-Mechanical Impedance (EMI) Based Structural Crack Monitoring

To detect small cracks in plate like structures, the high frequency characteristics of local dynamics were studied with the piezoelectric electro-mechanical impedance (EMI) method, and damages were monitored by the changes of the EMI. The finite element simulation model of EMI was established, and numerical analysis was conducted. The simulation results indicated that the peak frequency of the piezoelectric admittance signal is a certain order resonance frequency of the structure, and the piezoelectric impedance method could effectively detect the dynamic characteristics of the structure. The piezoelectric admittance simulation and experimental study of aluminum beams with different crack sizes were performed. Simulation and experimental results revealed that the peak admittance frequency decreases with the increase of crack size, and the higher resonance frequency is more sensitive to the small-scale damage. The proposed method has good repeatability and strong signal-to-noise ratio to monitor the occurrence and development of small-scale crack damage, and it has an important application prospect.