Resonance Frequencies Of Modes Research Articles

A Low-Profile Wideband Dual-Resonance Tri-Port MIMO Antenna

A low-profile wideband tri-polarized multi-input multi-output (MIMO) antenna is proposed in this communication. Based on characteristic mode analysis (CMA) of a circular patch, four slots are etched symmetrically on the patch to transform the high-order monopole-like modes into broadside modes with lower resonant frequencies. Four sets of shorting pins are also applied to simultaneously adjust the resonant frequencies of the monopole-like modes and broadside fundamental modes of the patch. The effects of the slots and the shorting pins on these modes are analyzed in detail. Three dual-resonance ports with high isolation are achieved by exciting three pairs of orthogonal modes of the patch. The proposed antenna is wideband with respect to its profile (bandwidth/height = 216), as facilitated by the dual-resonance property of each port. Experimental results show that the proposed antenna features high port isolation (>35 dB) and high gain (>5.58 dB). The proposed low-profile wideband tri-port antenna can be applied in highly integrated MIMO systems.

P93: Electrical Impedance for Accurate detection of degree of Ileus

Background: Postoperative ileus is a frequent complication of visceral surgery. It puts an additional financial burden on the U.S. health-care amounting to 1.5 billion dollars per year. A reliable way of assessing ileus is lacking. A highly sensitive electrical impedance-based measurement tool is presented. Methods: The system uses two coupled high Q-resonators (transmit resonator under the patient, receive resonator held by hand over the abdomen) as shown in Fig. 1(a). The normal mode resonant frequencies shift as the transmit receive distance changes. Over some range of separation distances, a constant, maximum efficiency can be achieved if the ideal operating frequency is selected (13.56MHz). This constant efficiency region corresponds to the V-shaped plateau as shown in Fig. 1(b-d). As the distance between the transmitting and receiving resonators changes, the frequency at which maximum efficiency occurs also changes. This allows for accurate distance measurement with 97% accuracy. Based on the dielectric properties of air, water, blood, and tissue at 13.56MHz we designed a phantom that simulates an abdominal cavity. The optimized coil geometries found in ANSYS Electronic Desktop 2021 R2 were implemented to fabricate the coils from copper via abrasive water jet cutting technology with the Flow NanoJet. Results: Reflection coefficients (S11 and S22) vs. distance vs. resonant frequency for the back and abdominal are shown in Fig. 2(b) and (c). The transmission coefficient (S21) between the resonators is shown in Fig. 2(d). The results indicate that as the distance between resonators changes, the resonant frequency changes as well. Abdominal girth was detected using an exponential regression model. Conclusion: An accurate predictive change of abdominal girth can be detected by electrical impedance in resonantly coupled regimen. This may aid in early detection and help in prognostication in cases of postoperative ileus.

Terahertz hybrid optical-plasmonic modes: tunable resonant frequency, narrow linewidth, and strong local field enhancement.

Hybrid optical-plasmonic modes have the characteristics of low loss and small mode volume, which will result in the strong localization and enhancement of electromagnetic field. Such advantages of hybrid optical-plasmonic mode are important for the enhancement of light-matter interactions. Here, terahertz (THz) hybrid modes of Fabry-Perot resonances (FPRs) and spoof surface plasmon polaritons (SSPPs) in the modified Otto scheme are investigated both in theoretical and experimental aspects. The device structure is composed of a metal grating silicon waveguide (MGSW) and a metal slit grating (MSG). The two components are vertically stacked with a variable air gap between them. The THz hybrid modes are originated from the far-field coupling of the FPRs and the SSPP supported by the air gap and the MSG, respectively. By changing the thickness of the air gap, the resonant frequency of the FPR-SSPP modes can be tuned in a frequency range of about 0.1 THz. An anti-crossing behavior between two reflection dips corresponding to the guided-mode resonance in the MGSW and the FPR-SSPP mode is observed, which leads to the narrowing of the reflection dips in the anti-crossing region. Numerical simulations show that at the resonant frequencies of FPR-SSPP mode, there is a huge volume-averaged electromagnetic energy enhancement of about 1600 times in the grooves of the MSG, which is around 8.7 times larger than that induced by the SSPP directly launched by free-space electromagnetic field. The hybrid FPR-SSPP modes can be used to construct THz sensors and detectors with high sensitivity.

Vibration analysis of MEMS vibrating mesh atomizer

Vibrating mesh atomizers (VMAs) are increasing in demand for various applications that require high quality droplet size distribution of aerosols. However, manufacturing limitations of metallic mesh atomizers have prevented researchers from investigating the dynamics and vibration analysis required to further enhance performance. Newly developed MEMS based VMAs allow these devices to be custom designed including varying aperture size, shape, and pitch as well as varying membrane dimensions. In this paper, a systematic vibration analysis of silicon-based MEMS based VMA was investigated to better understand the mechanisms of the atomization process and atomization rate. The MEMS atomizer consists of a microfabricated mesh on silicon membrane coupled with piezoelectric ring. The atomization process with this device is intricate to model due to combination of fluid transfer and dynamics of the membrane actuated by the piezoelectric ring. This paper uses multiphysics finite element modeling validated by experimental analysis to better understand the dynamics of the membrane and key parameters that affect the vibration analysis and atomization process. Resonance frequency, displacement, velocity, and mode shapes of the various dynamic modes of the atomizer were studied using finite element analysis and compared with the experimental results to validate the model. The results demonstrate a strong correlation between the modeled and experimental results of the resonant frequencies and atomization rates. The results can be used to design VMAs with enhanced performance for specific applications in the future.

Linewidth considerations for MEMS tunable VCSEL LiDAR.

The flexible membranes used in MEMS tunable VCSELs are so small and light that thermally induced vibrations can impact laser performance. We measure the thermal vibration spectrum of such a membrane showing peaks at the spatial vibration mode resonant frequencies of the membrane/plate. These vibrations result in a theoretical floor to the linewidth of the VCSEL. Frequency domain LiDAR and optical coherence tomography systems can get around this thermal linewidth limit with adequate clock measurement and processing. Essentially an OCT/LiDAR sweep with a concomitantly measured clock is a feed-forward linewidth reduction scheme. This can be achieved because the membrane resonances are relatively low frequency. LiDAR ranging out to 9 meters has been demonstrated with a resolution of 13 μm, close to the transform limit for the 70 nm sampling range.

Ray tracing and finite element modeling of sound propagation in a compartment fire

A compartment fire (a fire in a room or building) creates temperature gradients and inhomogeneous time-varying temperature, density, and flow fields. This work compared experimental measurements of the room acoustic impulse/frequency response in a room with a fire to numerically modeled responses. The fire is modeled using a Fire Dynamics Simulator (FDS). Acoustic modeling was performed using the temperature field computed by FDS. Room acoustics were modeled using two-dimensional ray and finite element modeling. A three-dimensional model was used to simulate an open flame. COMSOLTM Multiphysics was used for finite element acoustic modeling and BELLHOPTM for ray trace acoustics modeling. The results show that the fire causes wave-fronts to arrive earlier (due to the higher sound speed) and with more variation in the delay times (due to the sound speed perturbations). The resonance frequencies of low-frequency modes were shifted upwards. Model results are compared with data and show good agreement in observed trends.

Finite Element Analysis for Design Optimization of MEMS Double Ended Tuning Fork Resonator

A resonator design is very crucial for a resonant sensor since it affects the sensitivity, linearity, operational range, and resolution of the sensor. In this study, a DETF resonator is the object of analysis, to obtain a proper selection of boundary conditions and suitable structure for vibrational model. In order to achieve high Q values, proper vibrational mode selection is an important criterion for the operation of DETF resonator. This mode selection depends on the dimensional parameters, such as length, width, thickness, and gap of the tines of the DETF resonator. This paper presents a numerical approach-based analysis for obtaining optimum geometric configuration of a DETF resonator. The impact of DETF geometry on modal resonant frequency and mode separation is elaborated with the help of simulations using COMSOL Multiphysics tool.

Amplification of elliptically polarized sub-femtosecond pulses in neon-like X-ray laser modulated by an IR field

Amplification of attosecond pulses produced via high harmonic generation is a formidable problem since none of the amplifiers can support the corresponding PHz bandwidth. Producing the well defined polarization state common for a set of harmonics required for formation of the circularly/elliptically polarized attosecond pulses (which are on demand for dynamical imaging and coherent control of the spin flip processes) is another big challenge. In this work we show how both problems can be tackled simultaneously on the basis of the same platform, namely, the plasma-based X-ray amplifier whose resonant transition frequency is modulated by an infrared field.

Dynamics of Interfacial Bubble Controls Adhesion Mechanics in Van der Waals Heterostructure.

Two-dimensional van der Waals heterostructures (vdWH) can result in novel functionality that crucially depends on interfacial structure and disorder. Bubbles at the vdWH interface can modify the interfacial structure. We probe the dynamics of a bubble at the interface of a graphene-hBN vdWH by using it as the drumhead of a NEMS device because nanomechanical devices are exquisite sensors. For drums with different interfacial bubbles, we measure the evolution of the resonant frequency and spatial mode shape as a function of electrostatic pulling. We show that the hysteretic detachment of layers of vdWH is triggered by the growth of large bubbles. The bubble growth takes place due to the concentration of stress resembling the initiation of fracture. The small bubbles at the heterostructure interface do not result in delamination as they are smaller than a critical fracture length. We provide insight into frictional dynamics and interfacial fracture of vdWH.

The effects of caudal fin's bending stiffness on a self-propelled carangiform swimmer

The hydrodynamic performance of a self-propelled carangiform swimmer with a flexible caudal fin in the absence of a free stream is numerically investigated, where the fin's dimensionless bending stiffness varies from 10−3 to 150. It reveals that large flexibility of the caudal fin has a negative impact on the propulsion and moderate rigidity is found to increase the hydrodynamic performance. Two different vortex configurations are observed at low and high bending stiffnesses: (i) reverse Bénard–von Kármán (rBvK) vortex configuration and (ii) deflected reverse Bénard–von Kármán wake with the secondary vortex street, respectively. With the increase in bending stiffness, the thrust-producing part switches from the swimmer body to the caudal fin corresponding to the switch of the vortex configuration. Furthermore, the thrust and drag productions are examined. As the bending stiffness increases, the “active portion” of the caudal fin provides more kinetic energy to the wake flow. It is found that the deflected rBvK is induced by the vortical strength imbalance of two adjacent vortices, and the secondary vortex street is formed by the large strain between the primary vortex and the secondary vortex street. Meanwhile, the dynamic mode decomposition analysis indicates that the dominant mode of the dynamic flow field is the excited frequency resonant mode and the inherent frequency of the secondary vortex street is the same as the undulatory frequency. These results shed new light onto the role of the flexible caudal fin in self-propelled biological systems and may provide some inspirations to autonomous underwater vehicle design.

Lagrangian formulation to investigate the effect of coupling on resonant microstrip transmission line

AbstractAn analytical and a numerical study on coupling in microstrip transmission line (MTL) are reported for different split-gap orientations of a single gap square-shaped split-ring resonator (SRR). Taking both magnetic and electric couplings and adopting Lagrangian formulation for this coupled system, mathematical relations are found for each orientation of SRR to determine the connection between coupling co-efficient and resonant mode frequency. It is shown that coupling results in higher resonance frequency when the SRR, with parallel split-gap, has the gap far from the MTL. But, a lower resonance frequency is obtained when the SRR is placed at shorter distances with parallel split-gap near to the MTL. Again, for perpendicular split-gap orientation of SRR, the resonant frequency is found in terms of an effective coupling co-efficient; at shorter distances it is found to be lower than the fundamental resonance frequency of uncoupled SRR and an opposite effect is obtained at longer distances. Using CST Microwave Studio, the resonance frequency for each split-gap orientation of SRR is also studied as a function of separation between MTL and SRR. It is observed that this phenomenon strongly depends on SRR side-length, substrate height, and separation between MTL and SRR.

Addendum: Multiaxial resonant MEMS force sensor (2018 J. Micromech. Microeng. 28 105002)

In this letter we present an MEMS Sensor to measure displacement in at least two directions. The sensor device is a resonant, Lorentz force driven and cross-shaped sensing structure whereas the measurement signal equals the change of the resonance frequency induced by the deformation of the sensor-frame. This device is a pre-study to implement the sensor in a two-dimensional micro manipulation system for which the team uses a micro system analyzer to detect the resonance frequencies of the different vibration modes. The sensor-frame deformation between 0.1 and 2 µm is generated by four piezo actuators. With this setup, the sensor achieves a sensitivity of up to 20 nm Hz−1. The device is fabricated from a 100 mm SOI wafer with standard CMOS processes and has two Pt1000 elements integrated on the device layer to compensate any effects caused by thermal extension of the structure or temperature induced changes of material parameters.

Dipole Antenna With Both Odd and Even Modes Excited and Tuned

Dipole antenna is the simplest type of antenna from the theoretical point of view. However, the majority of the research on it focuses on adding supplementary structures to produce more resonant modes to achieve more functions. Here, we focus on the inherent modes of the dipole itself. Dipole antenna has alternating odd and even modes. In classical antenna theory, only odd modes are excited. The even modes are difficult to be excited due to their very high input impedances. In this article, both odd and even modes of the dipole antenna are excited simultaneously by a single port with a novel feeding structure. Moreover, to tune the resonant frequencies of such multiple modes, a method by combining antithetical structures of indentations and outdentations is proposed. Its principle is explained intuitively by eigencurrent distribution. By these new techniques, all the first six modes of a dipole are excited, among which five modes are used for Internet of Things (IoT) applications. The antenna can cover industrial, scientific, and medical (ISM) bands of 868 and 2450 MHz, global navigation satellite system (GNSS) band of 1575 MHz, and 5G bands of 3500 and 4900 MHz. This research could broaden the application of this classic antenna.

Design, Dynamics, and Optimization of a 3-DoF Nonlinear Micro-Gyroscope by Considering the Influence of the Coriolis Force.

In this paper, we use the nonlinear hardening stiffness of drive mode deal with the contradiction between gain and bandwidth of the linear micro-gyroscope, to improve the bandwidth and gain in sense direction. Firstly, in order to adjust the distance between two resonant peaks, we changed an incomplete two-degree-of-freedom(2-DoF) sense mode system of the micro-gyroscope into a complete 2-DoF system. Afterward, according to the given nonlinear coefficient of stiffness of drive mode, the structure size of driving micro-beams was designed to obtain a nonlinear micro-gyroscope with controllable stiffness. Finally, we investigated the effects of peaks spacing, damping, and driving nonlinearity on gain and bandwidth, and the nonlinear micro-gyroscope was optimized by orthogonal experiment method and response surface method. The results reveal that the peaks spacing has a great influence on the gain and bandwidth of both linear and nonlinear micro-gyroscopes. The larger the peaks spacing, the lower the gain, but higher gain can be achieved when the resonant frequency of the drive mode is close to the lower-order resonant frequency of the sense mode. Driving nonlinearity leads to the response peak of the Coriolis force to have a hardening characteristic, thus forming a wide platform in the sense direction. Hardening of the response peak of the Coriolis force allows the micro-gyroscope to obtain a higher gain while the bandwidth of the sense mode is also greatly improved. In addition, parameter optimization can make the gain and bandwidth of the micro-gyroscope optimal. When the peaks spacing is small and the nonlinear stiffness coefficient is about 1012.2, under the premise that the gain is basically constant, the bandwidth of the sense mode increases about 1.76 times compared with the linear gyroscope. Damping can suppress the influence of nonlinearity in a micro-gyroscope system. Within a certain range, the frequency response of the nonlinear micro-gyroscope tends to be a linear system with the increase in damping, resulting in narrower bandwidth and lower gain.

Impact of magnetic resonance force microscope probe on gyrotropic mode of magnetic vortex oscillations

We study the influence of magnetic resonance force microscope (MRFM) probe on the low frequency magnetization oscillations in a single permalloy disk connected with gyrotropic motion of magnetic vortex core. It is shown that the resonant frequency of gyrotropic mode can be tuned over a wide range by changing the distance between the probe and the sample. The possibility of switching the vortex core polarity under the action of the field of MRFM probe with large magnetic moment is demonstrated. The experimental data are analyzed using micromagnetic simulations and simple analytical models.

Propellant Mass Gauging via Modal Analysis on the International Space Station

In order for NASA to obtain sustained human presence in space, a higher fuel gauging accuracy is required. Current gauging methods have a sub 5-10% error which requires an additional fuel margin for any rocket or satellite. Doing this increases weight, therefore creating a higher cost. Gauging technologies capable of solving this problem either do not exist or only exist at low Technology Readiness Levels (TRLs). The Modal Propellant Gauging (MPG) project is an effort to develop a higher resolution, light-weight, and cost efficient fuel gauging method for low-gravity environments. MPG uses excited surface acoustic waves on the outside of the tank to measure the tanks resonant frequencies. In microgravity, the liquid will adhere to and coat the inner walls of the tank. The resonant mode frequencies are sensitive to the presence of liquid, meaning the accuracy of MPG is amplified in low-gravity. Modal measurements are taken using sensors adhered to the outer tank walls and a small data acquisition system. A Frequency Response Function (FRF) is then generated to create a reading for a fuel gauge.The newest iteration of MPG is Modal Propellant Gauging - International Space Station (MPG-ISS), which will undergo 30 days of autonomous testing onboard the ISS. This payload will implement MPG onto two tanks separated into two ISS payload lockers. A set amount of liquid will be transferred between both tanks as data is taken on both and stored on the in-flight computer. The MPG-ISS experiment will help validate the use of MPG on future space mission, such as Artemis. This experiment is the next step for MPG to be used on future mission to the Moon and Mars.

Measurement of the electric permittivity using Bleustein–Gulyaev wave sensor

We present a novel compact electric permittivity sensor that exploits Bleustein–Gulyaev waves propagating along the surface of shear-poled piezoelectrics. We formulate the dynamic nonlinear electromechanical partial differential equations of motion governing wave propagation under electromagnetically quasistatic conditions. The permittivity of the medium-under-test was found to influence the sensor eigenvalues, enabling the implementation of a frequency-shift permittivity sensor. Solution of the equations of motion demonstrates resonance of the first and third modes when excited using an interdigitated transducer. We fabricated two sensor prototypes on shear-poled PZT4 and LiNbO3 substrates and used a Vector Network Analyzer to observe the shift in their fundamental natural frequency in the presence of various media-under-test. S 11 measurements show deterministic and repeatable shifts in the resonant frequency of the first mode of the LiNbO3 sensor measured at MHz for ethanol and MHz for deionized water where the bare surface frequency was initially at MHz.

A MEMS Rate-Integrating Gyroscope (RIG) With In-Run Automatic Mode-Matching

Toward the objective of eliminating the angle error and rate threshold of the rate integrating gyroscope (RIG) caused by stiffness asymmetry, a novel in-run automatic mode-matching method is presented in this paper. Although other manual mode-matching methods can reduce the stiffness asymmetry temporarily, the environmental factors will interfere the manual calibration. Combined with virtual rotation, the processing circuits obtain the resonant frequencies of RIG operation modes and a controller is used to reduce the frequency difference. Meanwhile, an innovative method is proposed for RIG angle error analysis, avoiding the drawbacks of the traditional analysis methods. An FPGA based platform using a MEMS disk resonator is tested and the angle error is reduced to 1 degree compared with the manual calibration result 6.1 degrees.

A Kerr polarization controller

Kerr-effect-induced changes of the polarization state of light are well known in pulsed laser systems. An example is nonlinear polarization rotation, which is critical to the operation of many types of mode-locked lasers. Here, we demonstrate that the Kerr effect in a high-finesse Fabry-Pérot resonator can be utilized to control the polarization of a continuous wave laser. It is shown that a linearly-polarized input field is converted into a left- or right-circularly-polarized field, controlled via the optical power. The observations are explained by Kerr-nonlinearity induced symmetry breaking, which splits the resonance frequencies of degenerate modes with opposite polarization handedness in an otherwise symmetric resonator. The all-optical polarization control is demonstrated at threshold powers down to 7 mW. The physical principle of such Kerr effect-based polarization controllers is generic to high-Q Kerr-nonlinear resonators and could also be implemented in photonic integrated circuits. Beyond polarization control, the spontaneous symmetry breaking of polarization states could be used for polarization filters or highly sensitive polarization sensors when operating close to the symmetry-breaking point.

Nonlinear transmission line (NTL) model study of electromagnetic effects in high-frequency asymmetrically driven capacitive discharges

In this work, we generalize a nonlinear transmission line (NTL) model introduced in a previous work [Liu et al. Plasma Sources Sci. Technol. 30, 045017 (2021)] to achieve more comprehensive simulations. The improved NTL model allows a variable-sized (instead of a one grid cell) vacuum spacer between the powered and grounded electrodes and takes into account the (previously neglected) electron-neutral elastic collision frequency term in the plasma dielectric constant, and the radial variation of the plasma density. Using this model, we study the effects of the spatial and series resonances, associated with the (axially) z-antisymmetric and z-symmetric radially propagating surface wave modes, and the nonlinear harmonic excitations on the plasma uniformity. We conduct simulations in which we increase the driving frequency f from 30 to 120 MHz for an asymmetric capacitive argon discharge at a fixed pressure and electron power of pg=20 mTorr and Pe=40 W, respectively. The first antisymmetric mode resonance frequency fa1 occurs between 80 and 90 MHz, and the first symmetric mode resonance frequency fs1 occurs at about 100 MHz. The powered electrode sheath becomes smaller than the grounded electrode sheath for f≈fa1, and the source voltage reaches a minimum for f≈fs1. The radially varying electron power density shows a narrow center peak due to the finite mode wavelengths and the nonlinearly excited harmonics, which can be further enhanced by spatial or series resonances. A second peak appears above the vacuum spacer edge as f exceeds fs1 at 120 MHz because the shorter wavelengths at higher f allow secondary maxima of the surface waves to form within the reactor.