Resonance Frequencies Of Modes Research Articles

Electromechanical coupling and motion transduction in β -Ga2O3 vibrating channel transistors

We report on device physics modeling, assisted by experimental measurement results, for all-electronic transduction of resonant electromechanical motion of nanoscale β-Ga2O3 vibrating channel transistors (VCTs), including both direct readout of high frequency transmission current (without frequency down-conversion) and frequency modulation (FM) down-conversion techniques. The β-Ga2O3 VCTs under consideration have fundamental mode resonance frequencies at ∼25 MHz–1 GHz, with quality factors (Qs) of ∼100–5000 and transconductance gm at ∼0.2 nS–5 μS. In analysis of signal transduction with varying device parameters, the transistor's gate trench depth z0 and transconductance gm play key roles in improving the electromechanical coupling and device performance. Reduction of trench depth z0 can engender a major enhancement in readout current. Reducing channel thickness h and increasing channel length L can improve the readout current while downshifting the resonance frequency at the same time. We design β-Ga2O3 VCT with a suspended modulation doped field effect transistor structure for efficient operation in the GHz range. This study paves the way for future engineering of all-electronic transduction and integration of high frequency β-Ga2O3 resonators on chip with β-Ga2O3 electronics and optoelectronics.

Active control scattering manipulation for realization of switchable EIT-like response metamaterial

Electromagnetically induced transparency (EIT) is a promising technology that can improve the interaction between light and matter. The use of EIT-like in artificial functional microstructures considerably reduces the extreme requirements for the experimental observation of EIT-like spectra. In this paper, we proposed an active control electromagnetic modulator of the EIT-like spectrum induced by the metallic cut-wire metamaterial. Meanwhile, to realize switchable EIT-like behaviors, we used actively controlled scattering spectral modulation to create ”on/off” states and the specific operation is to rotate the “Y” shape symmetry metallic cut-wire metamaterial counterclockwise with a 30° step. We performed numerical calculations and detailed analyzes of the microscopic response of the metamaterial and showed the mode coupling between the electrical dipole resonances. Meanwhile, we have confirmed that the switching properties of the EIT-like spectrum can be significantly modulated under rather a small rotation angle at the transmission characteristic peak of the metamaterial and that the EIT-like resonance frequency modulation based on actively controlled scattering operation shows the advantages of extended metamaterial resonance modulation and operating frequency bands.

Effect of the wood anisotropy on eigenmodes and eigenvalues using finite element analysis – case of violin plates

The paper presents numerical studies performed with FEA related to the effect of wood anisotropy on vibration modes of violin plates made of spruce (Picea abies) and maple (Acer pseudoplatanus). The two-wood species are the traditional species for the top and back of the violins. In this study, three hypotheses – the material is isotropic; the material is transverse isotropic; the material is orthotropic, was used for modal analysis of violin plates. The plates were considered flat and having uniform thickness of 3 mm. Patterns obtained with modal analysis of violin vibration plates are illustrated for low frequencies modes and were compared to experimental results. The effect of anisotropy was illustrated by the variation of modal frequency of plates with the frequency of resonance modes. The difference between modal frequencies for the modes 6, 9, 10 and 12, calculated for the plate made of spruce and for the plate made of maple having orthotropic symmetry is respectively between 1.38% and 7%. For isotropic symmetry and for the same modes, this difference for the plate made of spruce and maple varies respectively between 57% and 18.92 %. The effect of anisotropy on the modal frequency of plate made of maple is more important than that on plate made of spruce.

MXene/SnO2 heterojunction based chemical gas sensors

Two dimensional (2D) MXene decorated by the SnO2 nanoparticles has been successfully synthesized by the hydrothermal method. The formed MXene/SnO2 heterojunction based chemirestistive-type sensors exhibit an excellent sensitivity and selectivity to different concentrations of NH3 from 0.5 to 100 ppm at room temperature. The enhanced sensing properties can be attributed to two major factors. On one hand, 2D MXene provides a matrix which has a unique, selective adsorption ability to ammonia and good conductivity that makes the room-temperature sensing of the heterojunction based sensor feasible. On the other hand, the difference in the Fermi level of the 2D MXene and SnO2 drives the charge transfer at the interface of the heterojunctions enriching the electrons on the surface region of SnO2 and consequently enhancing the sensitivity. Furthermore, a wireless sensor made from an inductor-capacitor (LC) antenna and the as-synthesized MXene/SnO2 heterojunctions fabricated by the low-temperature-cofired ceramic technique (LTCC) was preliminary investigated. The wireless sensor shows a even faster response/recovery speeds (<30 s) and more stable response to different concentrations of ammonia when the response was expressed in the mode of resonant frequency indicating a promising practical application.

Plasmonic modes in cylindrical nanoparticles and dimers.

We present analytical expressions for the resonance frequencies of the plasmonic modes hosted in a cylindrical nanoparticle within the quasi-static approximation. Our theoretical model gives us access to both the longitudinally and transversally polarized dipolar modes for a metallic cylinder with an arbitrary aspect ratio, which allows us to capture the physics of both plasmonic nanodisks and nanowires. We also calculate quantum mechanical corrections to these resonance frequencies due to the spill-out effect, which is of relevance for cylinders with nanometric dimensions. We go on to consider the coupling of localized surface plasmons in a dimer of cylindrical nanoparticles, which leads to collective plasmonic excitations. We extend our theoretical formalism to construct an analytical model of the dimer, describing the evolution with the inter-nanoparticle separation of the resultant bright and dark collective modes. We comment on the renormalization of the coupled mode frequencies due to the spill-out effect, and discuss some methods of experimental detection.

A Low-Profile Cylindrical Dielectric Resonator Antenna with Bandwidth-Enhancement under Triple-Mode Resonance

A low-profile cylindrical dielectric resonator antenna (CDRA) with enhanced impedance bandwidth is proposed via sharing a single triple-mode dielectric resonator. Initially, the resonant frequencies of TM 01δ and TM 02δ modes of a conventional CDRA are maintained far away from each other under central probe feed. Next, a circular disk with an annular ring is loaded around the conventional CDRA, aiming to excite an additional mode between these dual modes. The electric fields demonstrate that the previous TM 02δ mode is transformed into the TM 03δ mode for the modified CDRA, and an additional TM 02δ mode is successfully excited between the TM 01δ and TM 03δ modes. As a result, the resonant frequencies of these three radiative modes are reallocated in proximity to each other, thus achieving the desired bandwidth enhancement. In addition, considering the small input impedance of the CDRA, a microstrip feeding line is introduced underneath the central probe for good impedance matching. With these arrangements, the resultant antenna can generate an extended bandwidth under simultaneous radiation of TM 01δ , TM 02δ , and TM 03δ modes. Finally, the proposed CDRA is designed, fabricated, and measured to validate the predicted performance. The simulated and measured results show that the impedance bandwidth (|S 11 | < −10 dB of the antenna is dramatically extended from 8% to about 62% (2.83∼5.36 GHz), while keeping a stable conical radiation pattern. In particular, a low profile property of about 0.15 free space wavelength is achieved as well.

Grating Lobes Suppression in Frequency Selective Surfaces Using Electromagnetic Band Gap with Square Holes

Abstract In this paper, the authors present a proposal for an application of electromagnetic bandgap (EBG), for suppression of grating lobes, in frequency selective surfaces (FSS), not yet studied in the literature. An alternative type of EBG with square holes was proposed to reduce the computational effort in simulations. The study consists of an application of a rectangular periodic array of cylindrical and square holes in FSS dielectric substrate to create rejection bands and suppress specific resonant frequency modes. We built four prototypes and compared measured results with simulated results obtained with ANSYS HFSS. Simulations and measurements show suppression levels up to 6 dB. A good agreement between the results is observed. The FSS with EBG with square holes allows a simulation time 70 % lower than FSS with EBG with cylindrical holes.

Compact microstrip bandpass filters using triple‐mode resonator with lumped elements

AbstractCompact microstrip bandpass filters using triple‐mode resonator are investigated in this paper. At the center frequency of 2.45 GHz, a half‐wavelength microstrip open‐circuited resonator is loaded with a chip capacitor and a chip inductor to realize the triple‐mode resonator. By adjusting the resonator's parameters, the first three resonant mode frequencies could be tuned for bandpass filters with various fractional bandwidths. Three bandpass filters with different measured bandwidths (13.8%, 55.5%, 98.6%) are designed, fabricated, and tested to validate the design concept.

Dynamic analysis of flexural vibration mode of an atomic force microscope cantilever with a sidewall probe in liquid.

In this paper, dynamic behavior and the resonance frequencies of flexural vibration modes of an atomic force microscope cantilever with sidewall probe immersed in liquid to surface stiffness variations have been investigated and a closed-form expression is derived. Using numerical analysis, the flexural resonance frequencies of microcantilever immersed in liquid are calculated and the results are compared with the air environment. Then, the effect of sidewall length and normal stiffness on the frequency is investigated. Moreover, the surface-coupled effect between the cantilever and simple surface when the cantilever is close to the surface is considered and its effect on the quality factors of the first to fourth modes is studied.

Resonance frequency and radiative Q-factor of plasmonic and dielectric modes of small objects

The authors investigate the problem of electromagnetic scattering by small objects perturbatively starting from the electroquasistatic and magnetoquasistatic limits, and introduce closed form expressions for the resonance frequency and radiative Q-factor of plasmonic and dielectric modes.

Non-contact measurement of the thickness of a surface film using a superimposed ultrasonic standing wave

Most methods used to measure the thickness of thin liquid or solid surface films and coatings need access to the coated surface. In this work reflected ultrasonic pulses were used to measure a coating thickness from a solid back face. Piezoelectric transducers on the solid back face emitted ultrasound waves and received the waves that bounced off the front face. The magnitude of the reflected wave was dependent on the film thickness at the front face. Most pulse-echo ultrasonic approaches use the time-of-flight through the surface layer to determine its thickness. However, as the film becomes thinner, the reflected echoes overlap and there is often an acoustic mismatch between the solid and the surface film that reduces the signal strength. In this work, we propose the use of an ultrasonic continuously repeated chirp longitudinal wave to amplify the effect of the surface film. Multiple reflections interfere within the solid to form a superimposed standing wave whose amplitude spectrum is highly dependent on the surface film thickness thus overcoming the acoustic mismatch problem. Two bare 10 MHz piezoelectric elements were bonded to a 10 mm thick aluminium solid in a pitch-catch arrangement such that one continuously sends repeating chirp ultrasound waves and the other acts as the receiver. The transmitter was set to send a repeating chirp wave of 4 ms duration corresponding to the bandwidth of the transducer in order to maximise signal amplitude. The incident and reflected waves constructively and destructively interfere to form a superimposed standing wave within the solid. The solid/surface film to solid/air boundary condition frequency spectra ratio showed the film resonant frequency modes as minima. Using this technique epoxy coatings ranging from 70 μm to 350 μm were measured and showed a good correlation with independent measurements using a surface profilometer.

Current-controlled magnon propagation in Pt/Y3Fe5O12 heterostructure

We present a dynamic spin wave (SW) modulation technique using direct current (DC) to manipulate the magnetic properties of an ultralow-damping Y3Fe5O12 thin film. The microwave excitation and detection technique with two coplanar waveguide antenna arrangements on the Y3Fe5O12 (YIG) surface is used to characterize the SW. An additional platinum (Pt) stripe connected to a current source is integrated between the coplanar waveguide pair to demonstrate the SW resonant frequency and amplitude modulation by current induction. We selected a Pt stripe due to its significantly lower spin wave absorption property. The application of current through the Pt stripe generates local joule heating that modifies the magnetic properties of the YIG film. Temperature variation through local heating modifies the saturation magnetization of the YIG film, which, in turn, modulates the SW frequency. Moreover, the amplitude of the SW spectra is found to be tuned by the current amplitude. This phenomenon is mainly described by magnon–magnon scattering induced by the spin Seebeck effect in the case of local heating. Furthermore, the group velocity of the proposed device is also found to be responsive to the current, which has been explained by both magnon–magnon and magnon-phonon scattering.

Sensitivity and Directivity Analysis of Piezoelectric Ultrasonic Cantilever-Based MEMS Hydrophone for Underwater Applications

In this paper, we report on the characterization of the sensitivity and the directionality of a novel ultrasonic hydrophone fabricated by micro-electro-mechanical systems (MEMS) process, using aluminum nitride (AlN) thin film as piezoelectric functional layer and exploiting a stress-driven design. Hydrophone structure and fabrication consist of four piezoelectric cantilevers in cross configuration, whose first resonant frequency mode in water is designed between 20 kHz and 200 kHz. The MEMS fabricated structures exploit 1 µm and 2 µm thick piezoelectric AlN thin film embedded between two molybdenum electrodes grown by DC magnetron sputtering on silicon (Si) wafer. The 200 nm thick molybdenum electrodes thin layers add a stress-gradient through cantilever thickness, leading to an out-of-plane cantilever bending. A water resistant parylene conformal coating of 1 µm was deposited on each cantilever for waterproof operation. AlN upward bent cantilevers show maximum sensitivity up to −163 dB. The cross configuration of four stress-driven piezoelectric cantilevers, combined with an opportune algorithm for processing all data sensors, permits a finer directionality response of this hydrophone.

Wideband microstrip‐fed slot antenna with end‐fire radiation under dual‐resonant modes

In this paper, a microstrip-fed narrow slot antenna with end-fire radiation and expanded bandwidth under dual-resonant modes operation is proposed. At first, the open-ended slot radiator is studied and used to effectively suppress all the undesired even-order modes, reduce the antenna size, and form up the end-fire radiation pattern simultaneously. After that, by symmetrically introducing a pair of slot stubs near the electric-field distributions nodal lines of its second odd-order mode, the resonant frequency of second odd-order mode is gradually moved down. As such, the first and second odd modes could be effectively moved in proximity to each other, thus resulting in the improved impedance bandwidth of the slot antenna under dual-mode operation. To validate the predicted results, the proposed wideband microstrip-fed slot antenna is in final fabricated and measured. Both simulated and measured results are derived with good agreement. Measured results indicate that the impedance bandwidth of the slot antenna has achieved an immense enhancement up to about 25.5% (2.43-3.14 GHz). Moreover, the front-to-back ratio (FBR) beyond 6.0 dB has been successfully obtained across the whole operating band for end-fire radiation.

Studies on the vibration of Japanese drum wood barrels under material property uncertainty

Unlike isotropic material such as steel, wood behaves as a highly orthotropic composite material. Due to measurement difficulty, only the longitudinal Young's modulus and the specific gravity of the wood were successfully measured at the time the wood barrel was made. In the experiments, mode shapes and modal resonance frequencies were measured. In the numerical modal analysis, the finite-element model of the drum was constructed using orthotropic conical shell elements which require more elastic constants than those being measured. A try-and-error method was used to estimate those unknown constants by comparing the computed and measured modal frequencies and shapes. It was found that the estimated value of the circumferential (cross-grain) Young's modulus, which was unknown at the beginning of the study, turns out to be crucial in determining the lower mode resonance frequencies. The usefulness of this analysis is that the estimated elastic constants can be used for updating the finite-element model which can then be used for calculating the higher order modes. These higher modes cannot be practically determined by measurements. [Work by 2nd author supported by Miyamoto Unosuke Shouten Co.]

A Fixed-Frequency Angular Displacement Sensor Based on Dielectric-Loaded Metal Strip Resonator

A fixed-frequency angular displacement sensor using a dielectric-loaded metal strip resonator is proposed. The dielectric body on which the strip resonator is attached is a cylinder having a high dielectric constant (e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ≫ 1). The resulting resonator operates at the half-wave resonant frequency of the quasi-TEM mode of the loaded strip, which is much lower than the nominal resonant frequency of the strip. To enable angle sensing, the resonator is placed symmetrically between two 50 Ω, open-ended microstrip lines, so that the magnitude of the transmission coefficient(|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> |) between the lines varies with the strip angle, i.e., 0° ≤ θ ≤ 90°. Also, this configuration ensures constant resonant frequency operation for all angles. Simulations show that although the |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> | versus angle curve varies exponentially in the range of 0° ≤ θ ≤ 90°, the corresponding coupling coefficient varies quasi-linearly in 10° ≤ θ ≤ 80°. A laboratory prototype for ~ 2.4 GHz resonant peak is fabricated and the simulation results are verified through prototype measurement. The advantages of the proposed sensor are that it is compact, has a simple design, and operates at a fixed frequency, enabling a low-cost, robust angular sensor.

Transmittance spectrum in a semiconductor-superconductor quasi-periodic Thue-Morse one-dimensional photonic crystal

Based on the transfer matrix method and the two-fluid model, this study seeks to calculate the transmittance spectrum of a quasi-periodic one-dimensional photonic crystal (PC) composed of semiconductor (GaAs) and superconductor (HgBa2Ca2Cu3 O8+δ) layers. In particular, the arrangement of the PC layers follows a Thue-Morse sequence with a given periodicity. The critical temperature of the superconductor and the thickness of the semiconductor layers are dependent on the hydrostatic pressure, while the dielectric constant of the semiconductor is a function of both temperature and pressure. Our findings reveal the internal formation of forbidden regions of resonant mode frequencies in the transmittance spectrum and how the transmittance peaks exhibit a splitting after increasing the length of the Thue-Morse sequence. Finally, we demonstrate that as pressure increases the defect modes shift to higher frequency regions.

Dynamics Characterization of a U-Shaped Micro-Resonator Portal Frame

We present a study of the natural (resonance) frequencies of a tunable in-plane Microelectromechanical portal frame (U-shape) under DC electrostatic loads. The structure is designed and fabricated to excite the in-plane anti-symmetric (sway, first) and the symmetric (second) modes. Experimental results show high tunability of the resonance frequencies of both modes due to the electrostatic forces. Finite element simulations show good agreement with the experimental measurements. Further simulations are presented for the tunability of the natural frequencies of other higher-order modes using various electrode configurations. Frequency-response curves are presented for pure AC actuation of the first two modes showing strong nonlinear softening behavior due to the geometric nonlinearities of the portal frame. [2020-0269]

MEMS piezoelectric micro power harvester physical parameter optimization, simulation, and fabrication for extremely low frequency and low vibration level applications

In the last decade, the Piezoelectric Micro Power Harvesters (PMPH) has had a significant attention to produce self-powered small electronic devices at high frequency range. This paper discusses the effects of the PMPH control factor on the PMPH performances including Electric Energy Density and the Normal Electric Field using Taguchi optimization method. Furthermore, the study uses the ANOVA test and the Multivariable linear Regression model to confirm the Taguchi method. Also, it studies the PMPH with optimal control factor simulate through COMSOL Multiphysics 5.4 software. Then, it studies the PMPH first resonance frequency mode with Eigen-Frequency analysis. Moreover, the PMPH performances simulate in time domain through the transient analysis. Therefore, the PMPH is fabricated; it uses silicon substrate coated on both sides with a silicon nitride insulation layer, piezoelectric material is deposited on top of the insulation layer using the RF sputtering technique, the interdigitated gold electrodes (IDEs) are deposited using the DC sputtering, and a proof mass is used to lower the resonance frequency. Furthermore, the fabricated PMPH will be tested with base shaker experiment. Taguchi, ANOVA, and multivariable linear regression analyses results confirm each other. The paper concludes that the piezoelectric material, piezoelectric layer thickness, and silicon membrane thickness are the most three-factors influence the PMPH performances at low vibration levels and extremely low frequency about 1.2 Hz. On the other hand, the piezoelectric layer width and insulator width are the lowest control factors affect the PMPH performances. The PMPH with an optimum parameters simulation results as following, it vibrates at 2.59 Hz with an acceleration magnitude of 0.9 g and the maximum electric energy density of 400 Jm−3. The fabricated PMPH vibrates at the first resonance frequency of 1.2 Hz with acceleration magnitude of 0.9 g. Also, the study finds out that the optimum loading resister of 200 KΩ is found, associated with open-circuit voltage of 18.52 Vp−p. Also, the PMPH produces a maximum electric output power of 135 μW and maximum electric power density of 26.1 mWCm−3. The PMPH Simulation and fabrication results support each other and they demonstrate that the proposed PMPH can work probably at low vibration levels and at extremely low frequency about 1 Hz. Which makes the PMPH suitable for powering small electronic devices, such as cardiac pacemakers and other small medical implants.

Application of electromagnetic bandgap in frequency selective surfaces for suppression of higher‐order modes

AbstractIn this article, the authors present a proposal for the application of electromagnetic bandgap (EBG) for suppression of higher‐order modes in frequency selective surfaces (FSS), not yet studied in the literature. The study consists of an application of a rectangular periodic array of circular holes in FSS dielectric substrate to create rejection bands and suppress specific resonant frequency modes. We built four prototypes and compared measured results with simulated results obtained with ANSYS HFSS and it completes the proposed equivalent circuit validation. Simulations and measurements show suppression levels up to 10 dB. A good agreement between the results is observed.