Acoustic Oscillator Research Articles

Surface acoustic wave element, frequency filter, oscillator, electronic circuit, and electronic instrument

A surface acoustic wave element includes a single crystal substrate; a buffer layer formed by a crystal film that is formed on top of the single crystal substrate; and a piezoelectric thin film having a hexagonal system or a trigonal system crystal structure that is formed on top of the buffer layer. The surface acoustic wave element has an improved performance by improving the film quality of the piezoelectric thin film. In addition, because a semiconductor device can be formed on the single crystal substrate, the surface acoustic wave element can be integrated with the semiconductor device. Moreover, leakages of surface acoustic waves into the single crystal substrate are prevented. There are also provided a frequency filter, an oscillator, an electronic circuit, and an electronic instrument that are provided with this surface acoustic wave element.

Electrochemistry of Zeolites on Thickness Shear Mode Oscillators

This paper describes electrochemical studies of thickness shear mode (TSM) acoustic wave oscillators coated with zeolites. The frequency response of gold on AT-cut 9 MHz quartz oscillators of silver-ion-exchanged zeolite-modified electrodes (ZMEs) under an electrochemical bias is interpreted. This is achieved using a combination of cyclic voltammetry, double-potential-step chronocoulometry (DPSC), and the frequency and resistance responses of the quartz crystal oscillators. Three ZMEs were investigated including fully exchanged Ag(12)A plus partially exchanged Ag(6.4)A and Ag(3.5)A. In all cases, the frequency response of the quartz crystal nanobalance (QCN) could only be interpreted when motional resistance changes were considered. This determines the importance of energy storage and energy dissipation of the shear wave produced by the oscillator in the zeolite film, which was affected by the deposition of silver at the zeolite-electrode-solution interface. The silver deposit formed via the reduction of silver ions originally within the zeolite phase mechanically couples the zeolite film to the underlying substrate. The resistance changes occurring during redox are thus linked to an inner interfacial slip between the zeolite film and the underlying oscillating surface. The data presented are consistent with an extrazeolite redox mechanism.

Measurement of the strain-induced coefficient of permittivity of sapphire using whispering gallery modes excited in a high-Q acoustic sapphire oscillator

A low-loss monolithic sapphire has been developed for use as a novel transducer via the interaction between the electrical and mechanical resonances, with the intent of measuring the standard quantum limit in a macroscopic mass. This work has investigated the transductance mechanism due to the interaction between electrical and mechanical resonances in a low-loss electrical and acoustic resonator, which operates in the regime where parametric interactions dominate. High electrical and mechanical quality factors (Q-factors) are obtained at low temperatures (4.2 K) using high purity sapphire and single loop suspension vibration isolation. In deriving the displacement sensitivity of the monolithic sapphire transducer (MST), the acoustic mode shape and electromagnetic field distribution must be taken into account rather than the use of a simple mass–spring model. With the aid of this model we determine for the first time the strain-induced coefficient of permittivity for sapphire, both perpendicular and parallel to the c-axis. By comparison with other work, it has been determined that changes in the dielectric constant due to strain are approximately eight times smaller than changes caused by thermal expansion.

An implantable telemetry device to measure intra-articular tibial forces

Tibial forces are important because they determine polyethylene wear, stress distribution in the implant, and stress transfer to underlying bone. Theoretic estimates of tibiofemoral forces have varied between three and six times the body weight depending on the mathematical models used and the type of activity analyzed. An implantable telemetry system was therefore developed to directly measure tibiofemoral compressive forces. This system was tested in a cadaver knee in a dynamic knee rig. A total knee tibial arthroplasty prosthesis was instrumented with four force transducers located at the four corners of the tibial tray. These transducers measured the total compressive forces on the tibial tray and the location of the center of pressure. A microprocessor performed analog-to-digital signal conversion and performed pulse code modulation of a surface acoustic wave radio frequency oscillator. This signal was then transmitted through a single pin hermetic feed-through tantalum wire antenna located at the tip of the stem. The radio frequency signal was received by an external antenna connected to a receiver and to a computer for data acquisition. The prosthesis was powered by external coil induction. The tibial transducer accurately measured both the magnitude and the location of precisely applied external loads. Successful transmission of the radio frequency signal up to a range of 3 m was achieved through cadaveric bone, bone cement, and soft tissue. Reasonable accuracy was obtained in measuring loads applied through a polyethylene insert. The implant was also able to detect unicondylar loading with liftoff.

Resonant destabilization of phonon microwave stimulated emission in an acoustic quantum oscillator (phaser) with periodically modulated pumping

Two qualitatively different types of resonant destabilization of phonon stimulated emission (SE) are discovered in experiments where a 9-GHz multimode ruby laser is periodically modulated (the electromagnetic pump frequency is 23 GHz). In the case of deep pump modulation at low modulation frequencies (ω=70–200 Hz, where ωm is the modulation frequency), a fast random alternation of microwave phonon SE modes is observed. This destabilization range corresponds to relaxation resonance in optical lasers. Outside the relaxation resonance range (at ωm≈10 Hz), the other type of resonant destabilization of stationary phonon SE is observed. This destabilization shows up as very slow regular self-detunings of the microwave SE spectra. The period of such self-organized motions depends significantly on ωm and changes by several orders of magnitude when ωm varies within several percent. The second type of SE resonant destabilization is explained in terms of antiphase energy exchange between modes in a modulated phaser.

Experimental Quantization of Surface and Sub-Surface Structure in Float Polished Crystalline Quartz

Float polishing produces extremely flat (<λ/20) surfaces to atomic conformity over large areas. This process was applied to develop robust AT-cut, premium-Q, cultured, crystalline-quartz acoustic oscillators, which are normally highly susceptible to fracture from mechanical shock. The fabrication process was optimized to eliminate sub-surface damage, and to maximize the flexural strength of the crystals. We report premium results of a near-bulk value of stress-fracture threshold of 620 MPa, and a surface roughness of less than 0.2nm rms for 6.35mm diameter, 103.8µm thick samples float polished with colloidal silica. The remarkable surface quality produced by float polishing is combined with a 10-fold improvement in strength over blanks manufactured by the conventional CeO2 process. We also report on the characterization of the surfaces by atomic force microscopy, scatterometry, and photo acoustic spectroscopy where we see that deep 100µm removal eliminates damage from processing prior to the final float polish. These results are a significant improvement over the performance of commercially available resonators in equivalent tests.

Temperature Measurement Using a Dual Frequency Acoustic Delay Line Oscillator

An ultrasonic thermometer using a dual frequency (40 kHz and 25 kHz) acoustic delay line oscillator is described. The mean temperature along the acoustic delay line of 315 mm length with a spatial temperature gradient was quickly measured in order to verify the usefulness of the ultrasonic thermometer. In the monitoring which lasted for 125 min, mean temperature was measured using the acoustical method and was found to agree with the mean temperature simultaneously measured by 20 thermocouples. The average error during the monitoring was 2% or less.

Method and apparatus for wave therapy

An oscillator ( 12 ) of a low-frequency therapeutic apparatus ( 10 ) is controlled by a frequency control device ( 18 ) to generate a plurality of frequencies selected according to the kind of a disease and these frequencies are delivered from the lowest in an ascending order at intervals of a specified time, and are injected into a human body at the same time or separately as low-frequency electric currents from a therapeutic electrode ( 14 ) and an inactive electrode ( 16 ), as electromagnetic waves from oscillating coils ( 14 ) and ( 14 A), and as acoustic waves from an acoustic wave oscillator ( 62 ) and a body sonic apparatus ( 64 ).

Visible–blind photoresponse of GaN-based surface acoustic wave oscillator

We describe the photoresponse of GaN-based surface acoustic wave (SAW) delay-line oscillator operating in the 200 MHz range. The decrease in oscillator frequency under ultraviolet illumination of GaN transducer is caused by the SAW velocity decrease due to the acoustoelectronic interaction with photoconductivity electrons. The oscillator frequency shift reaches its maximum value at 365 nm and drops to zero above 400 nm with visible/ultraviolet rejection ratio more than 100. The optical quenching of the photoconductivity in GaN was observed. These results demonstrate the potential of the GaN-based SAW oscillators for applications as visible–blind remote UV sensors.

Radio frequency response of GaN-based SAW oscillator to UV illumination by the Sun and man-made source

A new solar-blind UV detector based on a GaN surface acoustic wave delay line oscillator is reported. The illumination by an artificial UV source in the presence of sunlight increased the RF spectral line width of the oscillator by almost an order of magnitude, which we attribute to the different noise spectra of these light sources. The output of this detector is a radio signal, which makes it especially attractive for remote sensing applications.

Rapid design of SAW oscillator electronics for sensor applications

This paper presents electronic techniques and a general methodology for the rapid design of two-port surface acoustic wave oscillators. By using a methodical approach, the stability problems and much of the time-consuming experimentation common to radio frequency (RF) oscillator design was avoided. Several oscillators in the range of 200 MHz to 1 GHz were designed using variations of the same basic circuit. Circuit designs included both two-port resonator and delay line SAW devices. The electronics were small in size ( 1.75 cm×1.75 cm ) and inexpensive (<US$ 10 in part cost). The active circuit element of the oscillators was a radio frequency integrated circuit (RFIC) wide-band amplifier. The first step of this systematic method was to identify a readily available RFIC amplifier that met the specifications of the oscillator. The specifications included amplifier gain, bandwidth and maximum input power. Choice of the proper amplifier allowed the same circuit to be used for several SAW oscillators spanning a large frequency range. Next a passive LC filter was designed to limit the open loop gain to a small frequency region around the SAW device’s fundamental frequency. This filter eliminates the problems of mode hopping and oscillation at harmonics. The S-parameters of the oscillator were then measured in an open-loop configuration to determine the phase shift requisite for the closed loop oscillation condition of 0° phase shift. To achieve stable oscillation, a passive LC phase-shifting filter was designed. Using the properties of Butterworth filters and a simple computer program, filters of exact phase shift were designed. The last step of design was the use of microstrip layout techniques to reduce wave reflections and susceptibility to electromagnetic interference.

Interactions of 6-aminopurine (adenine) in water and aqueous urea solutions

Density (ρ), ultrasonic velocity (U), viscosity (η), and absorbance (A) of adenine in water, 1 M, 3 M, and 6 M aqueous urea solutions have been measured in the presence (and absence) of different concentrations of salts, i.e., NaCl, KCl, and CaCl2. From these measured values, the apparent molar volume (ϕv), experimental slope (Sv), apparent molar compressibility (ϕK), viscosity coefficients A and B of Jones–Dole equation, specific acoustic impedance (Z), hydration number (Sn), internal pressure (Pi), molar absorptivity (ε), hypochromicity (h), and oscillator strength (f) have been calculated at 298.15 K. The increasing and (or) decreasing trends of all these parameters indicate a strong interaction of urea in moderate concentration (1 M and 3 M) with adenine especially at the hydrophilic/polar and ionic sites, particularly by hydrogen bonding. However, the interaction at hydrophobic sites are relatively weaker. Higher concentrations of urea (6 M) have more denaturation effect. The π–π interactions (stacking) in adenine are more prominent in concentrated solutions and are also strengthened by the presence of cations up to an optimum concentration of salts (cut-off point). The self-association of urea and adenine is more significant in concentrated aqueous solutions and becomes negligible on dilution.Key words: interaction, adenine, urea, density, viscosity, and ultrasonic velocity.

Interactions of 6-aminopurine (adenine) in water and aqueous urea solutions

Density (ρ), ultrasonic velocity (U), viscosity (η), and absorbance (A) of adenine in water, 1 M, 3 M, and 6 M aqueous urea solutions have been measured in the presence (and absence) of different concentrations of salts, i.e., NaCl, KCl, and CaCl2. From these measured values, the apparent molar volume (ϕv), experimental slope (Sv), apparent molar compressibility (ϕK), viscosity coefficients A and B of Jones–Dole equation, specific acoustic impedance (Z), hydration number (Sn), internal pressure (Pi), molar absorptivity (ε), hypochromicity (h), and oscillator strength (f) have been calculated at 298.15 K. The increasing and (or) decreasing trends of all these parameters indicate a strong interaction of urea in moderate concentration (1 M and 3 M) with adenine especially at the hydrophilic/polar and ionic sites, particularly by hydrogen bonding. However, the interaction at hydrophobic sites are relatively weaker. Higher concentrations of urea (6 M) have more denaturation effect. The π–π interactions (stacking) in adenine are more prominent in concentrated solutions and are also strengthened by the presence of cations up to an optimum concentration of salts (cut-off point). The self-association of urea and adenine is more significant in concentrated aqueous solutions and becomes negligible on dilution.Key words: interaction, adenine, urea, density, viscosity, and ultrasonic velocity.

On the acoustic nature of a microwave echo in silicate glasses

The results on the magnetic field dependence of the intensity of a microwave echo in silicate glasses containing paramagnetic impurities are used to construct a model of the formation of an echo as a super-position of an acoustic electron spin echo of the system of paramagnetic impurities and a polarization echo of the ensemble of quartz microcrystals present in the glass. Representing microcrystals in the glass as an ensemble of acoustic oscillators makes it possible to explain the anomalous low-temperature specific heat of glasses without invoking the model of localized two-level tunneling centers.

Deliberate use of distortion in singing

Singers are able to create aperiodic vibration of the vocal folds by either desynchronizing the primary oscillators (the vocal folds) or by engaging secondary sound sources (the false vocal folds, the aryepiglottic folds, or the velum). The desynchronization of the primary oscillators can be accomplished by creating a slight left-right asymmetry and then using the vocal tract (an acoustic oscillator) to entrain one vocal fold, leaving the other vocal fold to oscillate independently. Other aperiodicities can be created by driving the vocal folds at large amplitudes (with the critical parameter being A/L, the amplitude to length ratio of the vocal folds). In this mode of distortion, the highly nonlinear stress-strain characteristics of the vocal fold tissues are exploited. Infant cries, shouts, and groans are characteristic of this type of nonlinearity. Some videotaped examples and some computer simulations will be given to illustrate these phenomena.

Sapphire test-masses for measuring the standard quantum limit and achieving quantum non-demolition

In this paper we show that the available technology is sufficient to measure the Standard Quantum Limit (SQL) of a low loss acoustic oscillator, with a readout based on a microwave parametric transducer. The experiment makes use of the low electrical and acoustical losses in monocrystalline sapphire and new low-noise microwave technology. The crystal acts as an electrical vibration sensor and an acoustic oscillator in one monolithic structure. We analyze two new types of such structures: (1) The sapphire bar dielectric transducer and (2) the slotted sapphire dielectric transducer. We show that with a 40–60 dB double-cavity phase-noise suppression system the SQL may be measured using the sapphire bar. For the slotted structure, the phase noise requirements are less stringent because of its smaller resonant frequency and mass. We show that the SQL of this structure may be measured with a standard parametric readout. The principle of operation is demonstrated by some simple room-temperature experiments with all results verified using finite-element analysis.

Frequency stability enhancement from carrier-envelope resonance in a surface acoustic wave delay line oscillator

We have built a new injection-locking set-up which allows the study of low frequency noise in an oscillator. The interaction between a driving 100 MHz signal and a surface acoustic wave delay line oscillator undergoing a nonlinear modulational instability is investigated. Driving amplitude is used to control the synchronization range and therefore the frequency stability of a newly discovered carrier-envelope resonance process. In the soliton-locked regime, fundamental and subharmonic steps attached to a Lorentzian shape frequency-amplitude characteristic are found. They are explained thanks to a driven nonlinear Schrödinger model and the joined synchronization map.

Parametric back-action effects in a high-Q cyrogenic sapphire transducer

The construction and operation of a high-quality factor microwave sapphire resonator transducer coupled to a 1 kHz niobium membrane acoustic oscillator are presented in this paper. A four-stage passive vibration isolation system was included in the design to permit the measurement of the transducer’s parametric properties. The isolation system was shown to sufficiently suppress mechanical noise above 100 Hz and an upper limit to the displacement sensitivity of the transducer was measured to be 3.0±0.6×10−16 m/√Hz. The parametric behavior of the transducer with a single pump readout was measured for several transducer configurations, and the results were found to be in good agreement with theory. The measurements presented here display for the first time the complete parametric behavior in a high electrical Q system, where the transducer’s bandwidth is less than the mechanical oscillator’s frequency. The high stability and low losses of our system may allow the transducer to be configured as a back-action evasion or quantum nondemolition device.

Fabrication of a thick film sensor employing an ultrasonic oscillator

The paper describes the design and fabrication of a sensor using a thick film acoustic wave oscillator. The development of a screen printable piezoelectric paste is discussed and an account is given of the fundamental operation of acoustic wave resonant sensors, devices which have traditionally found application in higher-cost, precision applications. The electronic circuitry is also described and experimental results are presented to illustrate how a thick film delay-line oscillator can be used as a force sensor.

Phase locking of nonlinear monopoles with reactive coupling

Recently it was shown that a system of coupled nonlinear acoustic oscillators such as bubbles in a liquid may generate a coherent radiation starting from the initially incoherent state. However, such an active (radiative) coupling is typically weak, especially if the size of the system is smaller than the acoustic wavelength. Here a stronger, reactive coupling, such as an interaction of bubbles via the potential fluid motion around them, is considered. It is shown that an initial incoherent phase distribution is unstable only for the excitation level exceeding a definite threshold. For a nonlinear stage of generation a three-mode analytical model is used, permitting one to perform a phase-plane investigation of a system and to estimate the amplitude and duration of the generated coherent pulse. From the viewpoint of nonlinear dynamics, such an effect is an example of a ‘‘chaos–order’’ transition in a Hamiltonian system (although chaos may be just a lack of coherence). The role of small dissipation is also considered. Some estimates are made for the ensemble of bubbles in a liquid. a)Now at Univ. of Colorado at Boulder, CIRES, ETL/ERL/NOAA, 325 Broadway, R/E/ET, Boulder, CO 80303.