Variation Of Resonant Frequency Research Articles

Microwave dielectric properties of Ba 3La 2Ti 2Nb 2− xTa xO 15 ceramics

High dielectric constant and low loss ceramics in the system Ba 3La 2Ti 2Nb 2− x Ta x O 15 ( x = 0–2) have been prepared by conventional solid-state ceramic route. Ba 3La 2Ti 2Nb 2− x Ta x O 15 solid solutions adopted A 5B 4O 15 cation-deficient hexagonal perovskite structure for all compositions. The materials were characterized at microwave frequencies. They show a linear variation of dielectric properties with the value of x. Their dielectric constant varies from 49.8 to 45.1, quality factor Q u × f from 22,000 to 31,040 GHz and temperature variation of resonant frequency from + 6.9 to − 13.4 ppm/°C as the value of x increases. These low loss ceramics might be used for dielectric resonator (DR) applications.

DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF Mn DOPED (K, Na)0.96Sr0.02NbO3 CERAMICS

ABSTRACT Dense lead free ceramics with composition of (K0.5Na0.5)0.96Sr0.02Nb1-x MnxO3 (x = 0,0.01,0.02,0.03,0.04) were successfully prepared by conventional mixed oxide method, and their dielectric and piezoelectric properties have been investigated. The X-ray diffraction patterns indicated phase transition from peroveskite structure with orthorhombic symmetry to pseudo-tetragonal symmetry with increasing Mn content. Low loss tangent and relative high planar electromechanical coupling factor were obtained at x = 0.02 by the introduction of Sr and Mnion. The main parameters for the composition of x = 0.02 are: ϵ33 T/ϵ0 = 479, d33 = 121 kp = 41%, Qm = 298, tanδ = 1.6%, Tc = 391°C. The rates of resonant frequency variation, αfr, and planar coupling factor variation, αkp, with temperature 80°C are −1.85% and +1.19%, respectively. This material may be suitable for applications in ultrasonic transducers.

Passive Telemetric Readout System

A technique for remote query monitoring of environmental parameters such as pressure, humidity, complex permittivity, temperature, strain, and gases such as carbon dioxide, oxygen, and ammonia is presented. Resonant peak passive telemetry is used for wireless remote monitoring. The resonance frequency of an inductor-capacitor sensor circuit changes with the surrounding environmental parameter, and a detector circuitry, which employs a loop antenna, is used to remotely identify the resonance frequency. Mutual coupling between the antenna and the sensor inductor enables wireless monitoring. Various detection techniques available for monitoring the sensor resonance frequency are examined, and a new method is presented for automated and continuous wireless detection of sensor resonance frequency. Results are presented for different sensor resonance frequencies using various sensor capacitance values. The designed system can effectively detect sensor resonance frequency variation in the range of 20 kHz-10 MHz with the highest achievable resolution of 0.01 MHz. Sensor resonance frequency changes that occur faster than 1 s cannot be detected. The automated continuous wireless remote sensor platform design provides significant advantage over past systems, and the entire design is simple, easy to use, and widely applicable for in vivo, in vitro, and in situ monitoring

PSN-PMN-PZT 조성의 CeO2첨가에 따른 압전.유전특성 변화

0.03Pb<TEX>$(Sb_{0.5}Nb_{0.5})O_{3}-0.03Pb(Mn{1/3}Nb{2/3)O_{3}-(0.94-x)PbTiO_{3}-xPbZrO_{3}$</TEX> ceramics doped with <TEX>$CeO_{2}$</TEX> were synthesized by conventional bulk ceramic processing technique. Phases analysis, microstructures and piezoelectric properties were investigated as a function of <TEX>$CeO_{2}$</TEX> content (0.03, 0.05, 0.1 0.3, 0.5 and 0.7 wt%). Microstructures and phases information were characterized using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). Mechanical quality factor (<TEX>$Q_{m}$</TEX>) and coupling factor(kp) were obtained from the resonance measurement method. Both <TEX>$Q_{m}$</TEX> and <TEX>$k_{p}$</TEX> were shown to reach to the maximum at 0.1 wt% <TEX>$CeO_{2}$</TEX>. In order to evaluate the stability of resonance frequency and effective electromechanical coupling factor (<TEX>$K_{eff}$</TEX>) as a function of <TEX>$CeO_{2}$</TEX>, the variation of resonance and anti-resonance frequency were also measured using a high voltage frequency response analyzer under various alternating electric fields from 10 V/mm to 80 V/mm. It was shown that the stability of resonance frequency and effective electromechanical coupling factor were increased with increasing the <TEX>$CeO_{2}$</TEX> contents.

Diamond – Application to piezoelectric bimorph cantilever sensors

AbstractMicro‐cantilevers are excellent tools to measure tiny forces (from 1 nN up to 10 μN) as shown by the development of atomic force microscopy (AFM) techniques. That is the reason why micro‐cantilevers are also the most sensitive acoustic sensors. For instance, one can use the variation of the cantilever's resonant frequency to measure mass loading. In this work, we will show first why diamond is the most suitable material for a special type of cantilever sensors: piezoelectric bimorph cantilever sensors. In contrast to other cantilevers, it is possible to actuate piezoelectric bimorph cantilevers and to detect their resonance frequencies simultaneously. Then, we present one application of this type of cantilever: a diamond/AlN cantilever used as a high pressure sensor (up to 7 ar). The sensor operates by monitoring the frequency shift of the first resonant mode (f 1 ∼ 36.5 kHz). We have measured a sensitivity of 0.155 Hz/mbar in pure nitrogen. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Design and fabrication of multiband p-i-n diode switches with ladder circuits

Single-pole double-throw switches composed of p-i-n diodes are proposed for multiband operations. A ladder resonance circuit is introduced to simplify their configuration and to reduce the cost. The isolation greater than 20 dB and the insertion loss less than 2 dB are achieved in experiments at three frequency bands: 1.6, 2.5, and 5.8 GHz. Resonance frequency variations are investigated in detail for two types of switches consisting of: 1) lumped circuit elements and 2) semimicrostrip elements. The variations on the semimicrostrip configuration are about 25% of those with lumped circuit elements. The proposed switch does not influence the switching speed and signal distortion characteristics. It also showed good temperature stability from -30/spl deg/C to +85/spl deg/C.

Synthesis, Characterization, and Microwave Dielectric Properties of ATiO3 (A=Co, Mn, Ni) Ceramics

The ATiO3 (A=Co, Mn, Ni) dielectric ceramics have been synthesized by the conventional solid‐state ceramic route. The structure and microstructure of these ceramic samples have been studied using powder X‐ray diffraction and scanning electron microscopy. The microwave dielectric properties such as relative permittivity (ɛr), quality factor (Qu×f), and coefficient of temperature variation of resonant frequency (τf) of the ceramics have been measured in the frequency range 4–6 GHz using resonance methods. The dielectric constant of ATiO3 (A=Co, Mn, Ni) varies from 19 to 25 and τf close to −50 ppm/°C. The ceramics have high‐quality factors (Qu×f) of 62 500 GHz (at 5.42 GHz) for CoTiO3, 15 200 GHz (at 5.22 GHz) for MnTiO3, and 13 900 GHz (at 5.24 GHz) for NiTiO3, respectively.

Vibration analysis for piezoceramic rectangular plates using Ritz's method with equivalent constants

The transverse vibration of piezoceramic rectangular thin plates is investigated theoretically and experimentally using the Ritz's method incorporated with the defined equivalent constants. The equivalent constants are derived by comparing the characteristic equations of transverse resonant frequencies between isotropic and piezoceramic disks. By replacing the Poisson's ratio and flexural rigidity with the equivalent constants, the well-known Ritz's method can be used to investigate the transverse vibration of piezoceramic rectangular plates. Two different types of boundary conditions-clamped-free-free-free (CFFF) and clamped-free-clamped-free (CFCF)-are analyzed in this paper. For the experimental measurement, two optical techniques-amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV)-are used to validate the analytical results. Both the transverse vibration modes and resonant frequencies of piezoceramic rectangular plates are obtained by the AF-ESPI method. Numerical calculations using the finite-element method (FEM) are performed, and the results are compared with the theoretical analysis and experimental measurements. Excellent agreements are obtained for results of both resonant frequencies and mode shapes. According to the theoretical calculations with different equivalent Poisson's ratios, resonant frequency variations versus aspect ratios ranging from 0.1 to 10 also are discussed for the first several modes in the work.

Nucleation monitoring in cooling crystallization with a quartz crystal oscillator

A crystallization monitoring system using a quartz crystal oscillator was implemented in the cooling crystallization of dilute lauric acid solutions for the investigation of the nucleation process of the solute. In addition, the microscopic observation of the oscillator surface was conducted to examine the number and size of yielded nuclei, and the observed results and the resonant frequency variation of the oscillator were analyzed to explain the nucleation process. The change of the resonant frequency indicated the beginning moments of emulsification and nucleation of lauric acid near the oscillator surface. The experimental results show that the average crystal size was raised from 139 to 238 nm and the nucleation rate was reduced as the solution concentration increased from 0.05 to 0.25 g/L. When the solution temperature lowers, the crystal grows more rather than new nuclei form in the high concentration solution. The estimated crystal mass from microscopic observation ranges between 18% and 28% of that from the frequency measurement. It was also demonstrated that the proposed monitoring device is useful to investigate the crystallization process in dilute solutions, which often requires large analytical instruments.

Functional microwave flat antenna using alumina ceramic substrate and piezoelectric actuator

We have demonstrated a new-type microstrip patch antenna on a dielectric ceramic substrate with a mechanism of a variable antenna height using a mechatronics technology. The functional microwave flat antenna with an alumina ceramic substrate was controlled by a piezoelectric actuator, and changed the resonant frequencies. We have confirmed a possible variation of the antenna resonant frequency of 96% from 5.4 to 10.6 GHz.

RESONANT FREQUENCIES MONITORING OF ALKALI AGGREGATE REACTION (AAR) DAMAGED CONCRETE BEAMS

This paper deals with vibration based damage detection methods applied to AAR-affected structures within the framework of tests carried out on concrete beams made of reactive aggregates. The resonant frequency variations of the tested beams had been measured as the chemical reactions were progressing. Experimental results show evidence that the stiffness of the reactive beams first decreased significantly, subsequent increase up to the initial value was then observed. The relationships between the variations of the resonant frequencies and the physical properties are discussed taking into account water content effects, boundary conditions and the nature of the damage.

Tailoring the microwave dielectric properties of Ba(Mg 1/3Ta 2/3)O 3 ceramics

Ba(Mg 1/3Ta 2/3)O 3 (BMT) is a very important microwave dielectric resonator material with a high dielectric constant of about 25, high quality factor and small temperature variation of resonant frequency. The preparation temperature of BMT ceramics is relatively high, about 1650 °C. The microwave quality factor of BMT depends on the ordering of Mg–Ta–Ta ions on the perovskite B-site. In the present paper we report how one can tailor the properties of BMT ceramics by glass addition, slight non-stoichiometry and by dopant addition. (a) It is found that addition of small amount of glasses such as B 2O 3, ZnO–B 2O 3, ZnO–2B 2O 3, ZnO–B 2O 3–SiO 2 reduces the sintering temperature, increases density, order parameter and quality factor. (b) Slight Mg or Ba deficiency improves densification, order parameter and quality factor whereas excess Mg or Ba deteriorated the properties (c) Small amounts of dopants such as Sb 2O 5, MnCO 3, ZrO 2, WO 3, SnO 2 and ZnO improve the microwave dielectric properties. It is found that the quality factor is maximum when the ionic radii of the dopant ions are close to the weighted average ionic radii of B site ions (i.e. Mg 1/3Ta 2/3), which is 0.653 Å.

Vibrational spectroscopy and microwave dielectric properties of Ca5−xBaxNb2TiO12 and Ca5−xBaxTa2TiO12 ceramics

Complex ceramics Ca5−xBaxNb2TiO12 and Ca5−xBaxTa2TiO12 were prepared by conventional solid-state ceramic route. The crystalline structures were determined by x-ray diffraction, which showed that solid solutions were formed for x=4 (CaBa4Nb2TiO12 and CaBa4Ta2TiO12) and crystalline multiphases appeared for 1⩽x⩽3. The dielectric properties of the sintered ceramics were measured in the microwave frequency range. The dielectric constant and temperature variation of resonant frequency increased and the quality factor decreased with increasing x value. Raman analyses showed different spectra depending upon the composition, with variations in both intensity and frequency, as well as in the number of bands strictly related to the phases present. For both Nb- and Ta-based systems, the results indicated an increase in the short-range ordering with barium substitution, which explained the reduction in the unloaded quality factor (Qu). The results of far-infrared spectroscopy agree well with the Raman data, with few variations when Nb replaces Ta, and an increase in the complexity of the vibrational modes for Ca∕Ba mixed ceramics.

Investigation of the resonance frequency shift in parts with cracks

It is known that development of crack in various parts leads to resonance frequency variation and that phenomena can be used for crack detection and remaining lifetime prediction. We have investigated this effect on a steel specimen (25×150×6 mm). The crack was initiated at the root of preliminary machined notch and propagated under cycling loading on fatigue machine. The finite-element analysis was applied for calculation of frequency shift for three flexural modes of vibration and it was observed that the frequency shift increases with the increase of crack size. The maximum detected frequency shift was 3.8% for the crack size 23% of a sample width. The experimental measurements were conducted by measurements of sound produced by free vibration of the sample after impact excitation (impact resonance acoustic spectroscopy). The relative difference between acoustical measurements and FEA results did not exceed 1%. The conducted research provides a good basis for development of the remaining life prediction methods, for example, by Paris formulation. Parameters of the formulation for our case were determined experimentally. [Research supported by 21 Century Fund of Indiana.]

Theoretical and experimental vibration analysis for a piezoceramic disk partially covered with electrodes

Using the linear two-dimensional electroelastic theory, the vibration characteristics of partially electrode-covered thin piezoceramic disks with traction-free boundary conditions are investigated by theoretical analysis, numerical calculation, and experimental measurement. Four types of piezoceramic disks are discussed owing to the different electrode-covered distribution and electrical boundary conditions. It is found that when an alternating electrical potential is applied to the piezoceramic disk with axisymmetric partial electrodes, not only extensional but also transverse vibrations occur in resonance. The electrode-covered distribution influences the extensional vibration characteristics of piezoceramic disks; however, this phenomenon is not present for the transverse vibration. In this paper the optical speckle interferometry and electrical impedance analysis are employed to validate the theoretical analysis. Numerical calculations based on the finite element method are performed to make comparison with the theoretical and experimental results. According to the theoretical calculation, the variations of extensional resonant frequencies and dynamic electromechanical coupling coefficients depending on the various electrode-covered ratios are also investigated in this work. For the type with circular partial electrodes being connected, it is shown that the coupling coefficients will reach a maximum at the fundamental mode and drop to zero at the overtone mode for certain electrode-covered ratios.

Design, preparation and testing of suitable probe-receptors for RNA biosensing

Absolute measurements of a given RNA in a cheap, easy, rapid and reproducible manner using biosensors technology could overcome many of the operative and analytical limits of conventional molecular biology methods. To this end, an integrated approach for the design, synthesis, and connection of RNA probes to the transducing surface of a microgravimetric biosensor has been developed. Suitable probes to be used as the bioreceptors in RNA biosensor were successfully designed by using a purposely developed computational method whose selection criteria are based on the accessibility of target region to probe, on pairing stability of probe-target duplex and on the uniqueness of selected targets over all known expressed sequences from a genome data base. Automated chemical synthesis of selected probes was performed and the oligonucleotides produced were covalently conjugated to the sensing surface of a quartz microbalance. The microgravimetric sensor was tested in a flow chamber by measuring the variation of resonance frequency due to the binding of synthetic target substrates. Specific dose dependent binding was observed. Furthermore, the binding of a transcribed full-length mRNA substrate was successfully monitored under similar conditions.

Dew point measurement for organic vapor mixture using a quartz crystal sensor

A dew point measurement device for organic vapor mixtures using a quartz crystal sensor was proposed, and its performance was examined with acetone–methanol mixtures. The device has a sensor module to accommodate the quartz crystal sensor and a cooling system. The variation in resonant frequency of the sensor indicates the condensation of sample vapor, which tells the beginning moment of condensation, i.e., dew point. The measurement results with the proposed device were compared with the predicted dew points from the UNIQUAC equation and other experimental outcome to examine the performance of the device. Though some measurement error was yielded, it is proved that the proposed device is useful for measuring the dew points of organic vapors at different pressures.

Control orientated synthesis of high-performance piezoelectric shunt impedances for structural vibration control

Piezoelectric transducers are commonly used as strain actuators in the control of mechanical vibration. One control strategy, termed piezoelectric shunt damping, involves the connection of an electrical impedance to the terminals of a structurally bonded transducer. When subject to deflection, charge generated in the transducer flows through the external impedance developing a counteractive voltage across the terminals. Many passive, nonlinear, and semiactive impedance designs have been proposed that maximize this counteractive effect. This paper introduces a new technique for the design and implementation of piezoelectric shunt impedances. By considering the transducer voltage and charge as inputs and outputs, the design problem is reduced to a standard linear regulator problem enabling the application of standard synthesis techniques such as LQG, H/sub 2/, and H/sub /spl infin//. The resulting impedance is extensible to multitransducer systems, is unrestricted in structure, and is capable of minimizing an arbitrary performance objective. Experimental comparison to a resonant shunt circuit is carried out on a cantilever beam. Previous problems such as ad hoc tuning, limited performance, and sensitivity to variation in structural resonance frequencies are significantly alleviated.

Variations of the Magnetosphere Resonance Frequencies During Magnetic Storm of July 15——16, 2000

ULF observations at two mid-latitude sites during the large geomagnetic storm of July 15-16,2000 were used to trace variations of resonance frequencies of the field line resonators. A brief description of the geomagnetic disturbance as it was observed on the ground, at the geostationary orbit, and before the Earth's bow shock is given. Then a detailed study of ULF dynamic spectra from Borok and Mondy is performed for8 succesive 6-hour intervals of July 15 and 16. In conclusion some tasks for the future work are listed.

Transverse vibration analysis and measurement for the piezoceramic annular plate with different boundary conditions

Through means of the electroelastic theory for piezoelectric plates, the transverse vibration characteristics of piezoceramic annular plates with different boundary conditions are investigated in this work by theoretical analysis, numerical simulation and experimental verification. There are four different boundary conditions (free–free, fixed–fixed, free–fixed, and fixed–free) to be considered herein. With the aid of theoretical analysis, three groups of vibration modes are defined and employed for making the mode classification. Combined with the mode shape recognition, the classification is valid for the prediction of resonant frequency variations with various boundary conditions. Two experimental methods, laser Doppler vibrometer (LDV) and impedance analyzer, are applied to validate the theoretical results for the free–free boundary condition. From the experimental results, we find that the transverse vibration modes cannot be measured by the impedance analysis and only the extensional vibration modes will be shown. However, the transverse vibration modes of piezoceramic annular plates are obtained by the LDV system.