Showing papers on "Interdigital transducer published in 1997"

Microfabricated Lamb wave device based on PZT sol-gel thin film for mechanical transport of solid particles and liquids

Abstract: The fabrication using silicon micromachining and characterization of an acoustic Lamb wave actuator is presented. The intended use of the device is for mass transport and sensor applications. The device consists of dual interdigitated transducers patterned on a thin-film composite membrane of silicon nitride, platinum, and a sol-gel-derived piezoelectric ceramic (PZT) thin film. The acoustic properties of the device are presented along with preliminary applications to mechanical transport and liquid delivery systems. Improved acoustic signals and improved mass transport are achieved with PZT over present Lamb wave devices utilizing ZnO or AlN as the piezoelectric transducer.

Monolithic micromachined piezoelectric acoustic transducer and transducer array and method of making same

Abstract: A monolithic micromechanical piezoelectric acoustic transducer with integrated control circuit includes a support member; a piezoelectric medium disposed on the support member; first and second electrodes engaging the piezoelectric medium; and a control circuit monolithically integrated with the piezoelectric medium and electrodes on the support member and including a switching circuit for selectively interconnecting the electrodes with an I/O bus and a signal processing circuit for conditioning signals propagating between the electrodes and the I/O bus; an array of such acoustic transducers that form an acoustic retina; and a method of making such transducers and arrays.

Characteristics of liquids atomization using surface acoustic wave

Abstract: A novel way to produce dry fog using a surface acoustic wave transducer has been proposed. This atomizer is suitable for miniaturization and for producing a very small amount of mist to control atmospheric conditions. The device comprises a 4/spl times/8/spl times/0.6 mm/sup 3/ LiNbO/sub 3/ piezoelectric substrate. High frequency electrical power of 48 MHz is transformed into mechanical vibration using an interdigital transducer. The high frequency mechanical vibration produces a lot of small particles of liquid. The linear mean diameter of the mist was about 5 /spl mu/m. The atomizing rate was 170 /spl mu/l/min at 2.3 W input power.

Design techniques for SAW filters using slanted finger interdigital transducers

Abstract: This paper describes useful design techniques for wide-band linear phase SAW filters using slanted finger interdigital transducers (SFITs): to increase stop band attenuation, to flatten the pass band response, and to draw SFIT patterns for photo-masks. In order to increase stop band attenuation, a withdrawal-weighted SFIT is employed. A combination of a withdrawal-weighted SFIT and an unweighted SFIT provides good stop band responses, even though the number of finger pairs is small. In order to achieve a desired amplitude response in the pass band, an aperture-weighting technique for divided channels of SFITs is presented. A design method for drawing SFIT patterns for photo-masks is also described. A linear-phase SAW filter using SFITs with a 50% fractional bandwidth is designed and fabricated on 128/spl deg/ y-x LiNbO/sub 3/. A sidelobe suppression of 40 dB and a 3 dB to 40 dB shape factor of 1.12 were realized. Good agreement between theoretical and experimental results is obtained.

Acoustic wave enhancement of the catalytic oxidation of carbon monoxide over Pt{110}

Abstract: Clear evidence for the nonthermal acoustic wave enhancement of a catalytic reaction over a single crystal metal surface under controlled conditions is provided in this Letter. Data demonstrating a fourfold increase in the rate of CO oxidation over a thin Pt{110} catalyst bonded onto the surface of a piezoelectric interdigital transducer is discussed here together with a possible mechanism for this effect.

Surface acoustic wave filter device on 40° to 42° rotated Y-X LITAO3

Abstract: A surface acoustic wave device includes a piezoelectric substrate of a LiTaO3 single crystal, the crystal having X, Y and Z axes and a cut plane. The X axis of the crystal is oriented in a direction of propagation of surface acoustic waves. The cut plane of the crystal is rotated around the X axis at a rotated angle from the Y axis to the Z axis, the rotated angle being in a range between 40° and 42°. A pair of reflectors are formed on the substrate and aligned in a row in the direction of propagation. Interdigital transducers are formed on the substrate and aligned in the row in the direction of propagation, the interdigital transducers interposed between the reflectors, each interdigital transducer having pairs of mutually opposed primary electrode fingers and secondary electrode fingers, the interdigital transducers including at least a front transducer, a middle transducer and a rear transducer aligned in the row in the direction of propagation. In the device, a ratio of the number of pairs of the electrode fingers in one of the front transducer and the rear transducer to the number of pairs of the electrode fingers in the middle transducer is in a range between 55% and 80%.

Resonator-type surface-acoustic-wave ladder filter with improved upper stopband attenuation and reduced insertion loss

Abstract: In a resonator-type SAW filter, at least one series-arm SAW resonator has an interdigital transducer with reflectors on both sides, and the reflectors are separated from the interdigital transducer by a distance of from (N/2+0.55)λ 1 to (N/2+0.81)λ 1 , where N is an arbitrary non-negative integer and λ 1 is the wavelength of the surface acoustic waves excited by the SAW resonator. Alternatively, from 30% to 80% of the electrode fingers Constituting the interdigital transducer in at least one series-arm SAW resonator are apodized, dividing the interdigital transducer into an excitation region and a dummy region, and the electrode fingers in the dummy region are offset from the electrode fingers in the excitation region by a distance of 0.05λ 1 to 0.31λ 1 .

Surface wave liquid sensor

Abstract: A liquid sensor has comb-shaped electrodes (12, 14, 16, 18) which are arranged on a piezoelectric substrate (10) and act as interdigital transducers (20, 22) to generate an electroacoustic wave (24) from an emitting transducer (20) to a receiving transducer (22). The number of pairs of fingers of the interdigital transducer and the material of which the electrodes are made are selected in such a way that a surface shearing wave generated by the emitting transducer (20) and a volume shearing wave generated by the emitting transducer (20) have different frequencies.

Ultrasonic touch-position sensing device

Abstract: An ultrasonic touch-position sensing device comprises a piezoelectric substrate, two ultrasonic transducing units formed on an upper end surface of the piezoelectric substrate, and a signal controller connected with the ultrasonic transducing units. Each ultrasonic transducing unit consists of at least an input interdigital transducer and at least an output interdigital transducer. The output interdigital transducer has at least a finger-overlap zone R i (i=1). The finger-overlap zone R i comprises zones R ia , R ib and R im . The finger direction of the zones R ia and R ib runs parallel with that of the input interdigital transducer. The finger direction of the zone R im is slanting to that of the input interdigital transducer. When an electric signal is applied to the input interdigital transducer, an ultrasound is excited in the piezoelectric substrate, and transduced to electric signals E ia and E ib (i=1, 2, . . . , N) at the zones R ia and R ib , respectively. The input- and output interdigital transducers form N pairs of ultrasound propagation lanes Z ia and Z ib (i=1, 2, . . . , N), in the piezoelectric substrate, corresponding to the zones R ia and R ib , as well as to positions F ia and F ib (i=1, 2, . . . , N) on the upper- or a lower end surface of the piezoelectric substrate, respectively.

Efficient surface acoustic wave device capable of excitation in plural frequency bands, and signal receiver and communication system utilizing the same

Abstract: A surface acoustic wave device includes a piezoelectric substrate, a wave guide path provided on the piezoelectric substrate and an interdigital transducer for exciting a surface acoustic wave. The interdigital transducer is provided with plural portions of mutually different pitches of the electrode finger, respectively corresponding to different frequencies. The portions are parallelly arranged along a direction perpendicular to the propagation direction of the surface acoustic wave. The surface acoustic wave generated by the interdigital transducer is entered in concentrated manner into the wave guide path.

Shear horizontal wave device for sensing a touch-position

Abstract: An SH wave position-sensing device comprising two SH wave transducing units X and Y, a nonpiezoelectric plate and a signal controller. Each unit contains piezoelectric substrates P T0 , P R0 , P Ti (i=1, 2, . . . , N) and P Ri (i=1, 2, . . . , N), interdigital transducers T 0 , R 0 , T i (i=1, 2, . . . , N) and R i (i=1, 2, . . . , N). The interdigital transducers T 0 , R 0 , T i and R i , are formed on an upper- or a lower end surface of the piezoelectric substrates P T0 , P R0 , P Ti and P Ri , respectively. The lower end surface of each piezoelectric substrate is cemented on an upper end surface of the nonpiezoelectric plate. The finger direction of each interdigital transducer R i is slanting to that of each interdigital transducer T i . When an electric signal is applied to the interdigital transducer T 0 , an SH wave is excited in a bilayer zone B T0 formed by the piezoelectric substrate P T0 and the nonpiezoelectric plate, transmitted to a bilayer zone B R0 formed by the piezoelectric substrate P R0 and the nonpiezoelectric plate, and transduced to an electric signal with a phase θ base and delivered at the interdigital transducer R 0 .

Influence of step-like portions on the surface of ZnO/glass SAW filters on their frequency characteristics

Abstract: The frequency amplitudes of surface acoustic wave (SAW) filters mass produced of zinc oxide (ZnO) films on glass were found to be different among the filters even when their center frequencies are the same. We attempted various experiments In order to reduce the deviation of amplitudes. We accidentally found that the frequency characteristics and the amplitude deviation could be improved by mirror-polishing the ZnO film surface. In a SAW filter with a ZnO/interdigital transducer (IDT)/glass substrate structure, periodic step-like portions due to the thickness of the finger electrode of IDT and fine roughness were present on the ZnO film surface. As a result of investigating the effect of surface structure on amplitude deviation, the step-like portions did not affect the electromechanical coupling factors but reduced the SAW phase velocities, experimentally and theoretically. In addition, it was clarified that the step-like portions due to the finger electrodes and fine roughness on the ZnO surface caused deviations in the SAW velocities and their reflections, causing the deviation in the amplitude characteristics.

Thin film optical waveguide and optical deflecting device

Abstract: A thin film waveguide and an optical deflecting device which have a substrate and a waveguide layer. An optical buffer layer which has a refractive index smaller than that of the waveguide layer is provided between the substrate and the waveguide layer, and the optical buffer layer has such a thickness as to make a zero mode guided light beam progressing in the waveguide layer have a propagation loss not more than 2 dB/cm and as to make a first mode guided light beam progressing in the waveguide layer have a propagation loss not less than 4 dB/cm. For example, the waveguide layer is a ZnO thin film, the substrate is a silicon substrate, and the optical buffer layer is a SiO2 thin film. Further, an interdigital transducer is provided on the waveguide layer to excite Sezawa waves as surface acoustic waves. For example, the waveguide layer is designed to have a thickness which meets the following condition: 1.0

Multimode surface acoustic wave filter with a coupling section not being a uniform metal film

Abstract: The multimode surface acoustic wave filter includes two surface acoustic wave resonators closely arranged on a piezoelectric substrate in a direction perpendicular to the propagation direction of surface acoustic waves and acoustically coupled by a coupling section, each of the surface acoustic wave resonators including an interdigital transducer and two reflectors disposed closely on both sides of the interdigital transducer in a direction parallel to the propagation direction of the surface acoustic waves, the interdigital transducer having an excitation section for exciting the surface acoustic waves and a signal terminal section for inputting an electric signal, each of the reflectors having a grating section and a terminal section, wherein the velocity of surface acoustic waves propagating through the coupling section is a little larger than the velocity of the surface acoustic waves propagating through the excitation section of the interdigital transducer.

A new manipulator based on surface acoustic wave streaming

Abstract: This paper reports a new micromanipulator based on surface acoustic wave (SAW) streaming. When a small solid object is placed with a water droplet on SAW substrate and SAW is excited, the object can move easily and smoothly with the droplet in the SAW propagation direction. Small steel balls from 0.5 to 4.0 mm diameters were examined as manipulating samples on a SAW substrate. The experimental results are compared with conventional SAW motor method based on friction drive, with which the object is moved toward operating interdigital transducer (IDT)-which is opposite to SAW propagation direction. As a result, the driving force of the present method was found to be sixty times as large as that of the conventional SAW motor method. Moreover, teflon sheet, being difficult for the conventional SAW motor method, can be moved with ease for the present method. We conclude that the present method must have high potential to be use in practice as a micromanipulator.

The experimental and theoretical characterization of SAW modes on ST-X quartz with a zinc oxide film layer

Abstract: The Y-rotated, X-propagating, (ST-X), cut of quartz is used extensively for the development of surface acoustic wave (SAW) devices where temperature stability is of primary importance. Besides the commonly used generalized SAW (GSAW) mode, this crystal cut also supports a pseudo-SAW (PSAW) and high velocity pseudo-SAW (HVPSAW) mode. All three predicted SAW modes have been observed in ST-X quartz using an interdigital transducer configuration, with and without a zinc oxide film layer, and the SAW compared with theoretical. There was excellent agreement between experimental and theoretical velocity values without the ZnO film layer. There was good agreement between experimental and theoretical velocity dispersion characteristics in the presence of the ZnO film layer for the GSAW mode. The viscosity values for quartz were introduced into the complex elastic constants to theoretically predict and correlate with propagation loss for the three SAW modes with and without the ZnO films. The trends predicted by the theoretical calculations were strongly evident in the measured data particularly in the PSAW and HVPSAW modes where the presence or absence of the ZnO film represented an order of magnitude difference in the propagation loss. The frequency dependencies of the measured propagation losses correlated well with the predicted frequency dependencies. Differences in absolute loss values between theory and experiment were attributed to diffraction losses, air loading, and the absence of viscosity values for the ZnO film.

Vorrichtung und Verfahren zum Bestimmen des Alterungszustands flüssiger Medien

Abstract: The invention relates to a sensor device for determining material parameters of a liquid medium, comprising two interdigital transuducers (12, 14) for generating an electroacoustic wave from the one (12) interdigital transducer to the other (14) interdigital transducer. The two interdigital transducers (12, 14) are connected to a first evalutation circuit to determine the viscosity, viscoeleasticity and/or density of the liquid medium on the basis of the resonance frequency determined and/or the damping of the electroacoustic wave. One of the interdigital transducers (12) is also connected to a second evaluation circuit for determining the dielectric constant and/or the conductivity of the liquid medium on the basis of the complex electric impedance of said interdigital transducer (12). A frequency different from the resonance frequency of the electroacoustic wave is used to determine said complex electric impedance by means of the second evaluation circuit.

Wafer fabricated electroacoustic transducer

Abstract: A capacitive electroacoustic transducer (10) which includes an electrically insulative substrate (19), a layer of conductive material disposed (16) on a portion of a top surface of the substrate forming a first electrode of the transducer, a conductive diaphragm (22) forming a second electrode of the transducer which is deflectable in relation to the first electrode, and a structure (18) for electrically and physically separating the first and second electrodes in spaced relationship so as to constitute a capacitor. This transducer exhibits a high degree of thermal stability partly due to the substrate and diaphragm being made of materials having closely matched thermal expansion coefficients. This feature ensures that the tension in the diaphragm stays consistent even with varying temperatures, thereby maintaining a constant transducer sensitivity. In addition, the distance separating the first and second electrodes is minimized so as to create a short thermal expansion path. This short path length minimizing changes in the response of the transducer due to variations in temperature. This transducer can also be batch produced.

Surface acoustic wave filter having input and output transducers with different aperture lengths

Abstract: A surface acoustic wave filter is provided which performs balanced signal/unbalanced signal conversion The input and output impedances are different from each other In a surface acoustic wave filter of the longitudinal mode type, a signal is applied to two terminals of an input interdigital transducer, or a signal is output from two terminals of an output interdigital transducer, thereby consituting a balanced type filter The aperture length of the input interdigital transducer is different from that of the output interdigital transducer

Ultrasonic transducer array incorporating an array of slotted transducer elements

Abstract: An ultrasonic transducer array having a plurality of transducer elements aligned along an array axis in an imaging plane. Each transducer element includes a piezoelectric layer and one or more acoustic matching layers. The piezoelectric layer has a concave front surface overlayed by a front electrode and a rear surface overlayed by a rear electrode. The shape of each transducer element is selected such that it is mechanically focused into the imaging plane. A backing support holds the plurality of transducer elements in a predetermined relationship along the array axis such that each element is mechanically focused in the imaging plane.

Surface acoustic wave device for sensing a touch-position

Abstract: A surface acoustic wave (SAW) position-sensing device comprising a piezoelectric substrate, an input interdigital transducer (IDT) T formed on an upper end surface of the piezoelectric substrate, and an output IDT R formed on the upper end surface of the piezoelectric substrate such that the finger direction of the IDT R is slanting to that of the IDT T by an angle α. The thickness d of the piezoelectric substrate is larger than three times an interdigital periodicity P of the IDT T. An interdigital periodicity P N along the vertical direction to the finger direction of the IDT R is equal to the product of the interdigital periodicity P and cos α. An overlap length L P along the finger direction of the IDT R is equal to the product of an overlap length L of the T and sec α. When an electric signal is applied to the IDT T, the SAW is excited on the upper end surface of the piezoelectric substrate, and is transducer to electric signals E j with phases θ j by the IDT R, the phases θ j corresponding to positions F j . The total phase Σθ j made by the phases θ j , and the total electric signal ΣE j made by the electric signals E j are zero. The IDT T and R form minute propagation lanes Z j , corresponding to the positions F j , of the SAW on the upper end surface of the piezoelectric substrate. If touching a position F x on a minute propagation lane Z x , an electric signal E with a phase θ is delivered from the IDT R. The position F x corresponds to an electric signal E x with a phase θ x , the electric signal ΣE j minus the electric signal E x being equal to the electric signal E, the phase Σθ j minus the phase θ x being equal to the phase θ.

Surface acoustic wave apparatus having an interdigital transducer ground electrode connected to multiple package grounds

Abstract: A surface acoustic wave apparatus includes first and second longitudinally-coupled resonator filters disposed on a surface-wave board. In each longitudinally-coupled resonator filter, the ground electrodes of IDTs disposed at opposite sides of the center IDT and adjacent to reflectors are connected to different ground electrodes located on the same layer in the package, with at least two bonding wires.

Propagation Characteristics of Surface Acoustic Waves in KNbO3/SrTiO3/Si Layered Structures

Abstract: The propagation characteristics of surface acoustic waves (SAWs) in KNObO3/SrTiO3/Si structures were investigated theoretically. Phase velocities (v p) decrease when the hK value of the SrTiO3 buffer layer increases from 0.04 to 0.2 for a specified thickness of the KNbO3 film. The value of the coupling coefficient (K2) can be as high as 10%. A layered structure with the interdigital transducer (IDT) located on top of the KNbO3 film is a better choice for device fabrication if we select a coupling coefficient of 1% as a reference for comparison. The results could provide useful information for combining optical devices, semiconductor devices and SAW devices on the same Si substrate.

A new focusing ultrasonic transducer and two foci acoustic lens for acoustic microscopy

Abstract: The textured piezoelectric film of a new organic-based material produced by vapor deposition was used as an active element of a focusing ultrasonic transducer. The transducer exhibits near theoretical lateral and axial resolution, unipolar pulse response to a step voltage, and 30 dB insertion losses in an octave frequency band. The transducer is acoustically transparent over a wide frequency range and can be fabricated on a concave spherical surface of the standard acoustic lens. The resulting double transducer and two foci acoustic lens are capable of improving the quality of the surface structure imaging or of being used in continuous wave reflection acoustic microscopy.

A new ultrasonic composite transducer implemented with thick film technology

Abstract: A new ultrasonic transducer operating in air and fabricated by thick film technology is presented. It consists of a composite mechanical structure in which three active elements, made with planar alumina substrates supporting PZT-based piezoelectric films, behave as elastic guides. The active elements have a constant rectangular cross-section and are radially placed, 120/spl deg/ apart. They are mounted between a rigid base (operating as the acoustic backing) and an alumina disk. On both sides of each substrate a piezoelectric layer has interdigital thick-film electrodes embedded in layer itself, so that it can be polarized parallel to the long side of the active element; consequently, it allows the creation of periodic surface stresses responsible for symmetric extensional strains in the alumina plates. The elements, synchronously driven in phase, form, with the disk, a vibrating resonant structure, which radiates acoustic energy perpendicular to the disk surface. The assembly of active elements, acoustic backing and radiating disk forms a composite ultrasonic transducer operating in air without the need of any acoustic matching layer. Among the prominent features offered by the transducer design are: a transduction efficiency of 25% at an exiting voltage of 100 V/sub p/ and a high directivity of the emitted beam.

Surface acoustic wave device with a resistor thin film to remove pyroelectric effect charges

Abstract: A surface acoustic wave device includes a piezoelectric substrate, an interdigital electrode pattern, and a resistor thin film. The piezoelectric substrate has a piezoelectric effect. The interdigital electrode pattern is made of a conductive thin film and formed on the piezoelectric substrate to perform conversion between an electrical signal and a surface acoustic wave. The resistor thin film is formed on the piezoelectric substrate to electrically connect the piezoelectric substrate to the interdigital electrode pattern. The resistor thin film serves to remove charges from a surface of the piezoelectric substrate due to a pyroelectric effect to the interdigital electrode pattern.

Preparation and Piezoelectricity of c-Axis Oriented LiNbO3 Thin Films on Polycrystalline Si3N4 Substrates

Abstract: C-axis orientation of LiNbO3 thin films prepared on polycrystalline Si3N4 substrates by RF magnetron sputtering was optimized by analysis of the variance. The LiNbO3 thin film was completely oriented in the c-axis direction. Using an interdigital transducer fabricated on the film, a resonance was observed at a frequency of 800MHz, which showed that the film exhibited piezoelectric properties. It was proved that a c-axis-oriented LiNbO3 thin film can be used to detect mechanical impact.

Surface acoustic wave device and portable telephone using same

Abstract: The surface acoustic wave device of the invention comprises a piezoelectric substrate of lithium niobate or lithium tantalate and electrodes formed on the substrate for propagating surface acoustic waves. The substrate has a cut plane and a surface acoustic wave propagation direction which are (φ, θ, ψ) as expressed in Eulerian angles and within ranges substantially equivalent thereto. When the substrate is made of lithium niobate, φ, θ and ψ are 0°-86° or 95°-180°, 73°-118° and 0°-44°, respectively. When the substrate is made of lithium tantalate, φ, θ and ψ are 0°-87° or 91°-180°, 80°-120° and 0°-44°, respectively. This enables the device to exhibit high performance.

Effect of a buffer layer on the surface acoustic wave characteristics of Pb(Zr,Ti)O3 film/buffer layer/semiconductor substrate structures

Abstract: The effect of a buffer layer on the surface acoustic wave properties of Pb(Zr, Ti)O3 (PZT) film/buffer layer/ semiconductor substrate structures was examined theoretically. Large coupling coefficients (2.8–3.4%) can be obtained when the interdigital transducer (IDT) is on top of the PZT film, with (type 4) and without (type 3) the floating-plane electrode at the PZT film-buffer layer interface. In the type 4 IDT configuration, there exists a minor peak of the coupling coefficient when the hK value of the PZT film is about 0.3. The minor peak values of the coupling coefficient (0.62–0.93%) decrease when we increase the thickness of the buffer layer from 0 to 0.25. These results could be useful for the further development of ferroelectric devices, semiconductor devices and SAW devices on the same substrate.

Piezoelectric materials for application in low profile interdigital transducer designs

Abstract: This paper presents a comparative study between piezopolymer (PVDF) and piezo-platelet active layers in flexible interdigital transducer (IDT) designs for the generation of ultrasonic Lamb waves in thin plate structures. Initially, the pulse-echo response in steel was evaluated, where the piezo-platelet transducer demonstrates significant sensitivity advantage over the PVDF devices. The mechanical behaviour of each transducer was further investigated using a laser interferometer scanner to measure surface displacement and evaluate the extent of cross coupling and electrode pattern on the IDT response. Furthermore, finite element modelling has been utilised to evaluate the IDT coupling efficiency for the generation of a particular ultrasonic Lamb wave mode. Interestingly, it is shown that the properties of each transducer tend to be complementary with respect to a particular application. The piezo-platelet materials possess distinct advantages for generation of in plane, symmetric modes, especially for operation in composite plates, while the PVDF, although less efficient, has advantages with regard to cost and flexibility for the generation of anti-symmetric modes in metallic plates.