Showing papers on "Interdigital transducer published in 2000"

The rapid monitoring of structures using interdigital Lamb wave transducers

Abstract: The use of interdigital PVDF transducers for the quick inspection of large, plate-like structures is discussed. The transducers are designed to excite a particular Lamb mode in the structure, the region of the structure that is insonified being controlled by the transducer design. An example is given of the monitoring of an aluminium plate by a single, circular transducer operating in pulse-echo mode, the a0 Lamb mode at a frequency of about 1 MHz being transmitted and received. The transducer is split into segments so that the angular location of a reflector can be defined, the radial location of the reflector being determined from the time of arrival of the echo.

Surface acoustic wave device

Abstract: A surface acoustic wave device includes a piezoelectric substrate (2), and an interdigital transducer (3) provided on the piezoelectric substrate (2), wherein the piezoelectric substrate (2) includes at least two piezoelectric ceramic layers made of a polycrystalline material. The at least two piezoelectric ceramic layers are stacked so that electrical characteristics and mechanical characteristics thereof vary in a direction that is substantially perpendicular to a surface of the piezoelectric substrate (2) upon which the at least two ceramic piezoelectric layers are stacked.

Acoustic streaming in micromachined flexural plate wave devices: numerical simulation and experimental verification

Abstract: This paper presents the numerical simulation and experimental validation of acoustic streaming in micromachined flexural plate wave (FPW) devices. Two-dimensional and three-dimensional models of two device types were considered: the classical device with parallel interdigitated electrodes and the focused device with curved electrodes. Influences of different parameters on the time-averaged velocity were investigated. Thermal transport effects of the acoustic streaming were also considered. We observed the amplifying effect of the streaming in the second type numerically and experimentally. To verify simulation results, the method of the particle image velocimetry (PIV) was applied in the experimental investigation.

Wireless pressure and temperature measurement using a SAW hybrid sensor

Abstract: A passive pressure and temperature sensor unit based on the combination of a SAW reflective delay line with a high-Q capacitive pressure sensor is presented. Due to a symmetric arrangement of the impedance loaded splitfinger interdigital transducer (IDT) between two reference reflectors a temperature corrected evaluation of the pressure signal is enabled. A prototype of a tire pressure sensor unit is shown. In combination with a wheel arch antenna and a conventional transceiver unit a typical signal-to-noise rate of 20 dB resulting in a pressure accuracy of /spl plusmn/15 kPa was measured.

Surface-wave transducer device and identification system with such device

Abstract: The invention relates to a surface-wave transducer device—also called TAGs—and to identification systems with this device. DE 42 17 049 discloses a passive surface sensor which can be interrogated in wireless mode. In this context, energy is transmitted by radio to the sensor using an interrogation device, the interrogation being done by means of chirped transmission signals. The sensor has transducers and reflectors. The reflectors reflect the chirp signal in a time-staggered sequence, so that the sensor returns a time-staggered chirp signal to the interrogation device. The reflection principle means that the surface-wave sensor described above (also called SAW—surface acoustic wave—sensor in the following text) has a very high insertion loss of the order of 50 dB, for example. When the chirp signal has been received by an SAW interdigital transducer as the input transducer, this transducer produces a surface wave which propagates on the substrate of the SAW arrangement in the direction of the reflectors. When an SAW is received, each individual reflector element returns a correspondingly reflected SAW to the SAW transducer, which for its part produces an electromagnetic signal from the SAW. However, since each reflector element returns not just one SAW to the SAW transducer, but rather the reflector elements also reflect signals amongst one another, the reflections are inevitably relatively small, and a large part of the energy coming from the SAW transducer is lost in the reflector arrangement, so that only a low output power can be achieved. The problem of “internal reflection” from the reflectors cannot be avoided in principle. The object of the invention is to provide a surface-wave transducer device which has a low insertion loss, allows a considerably greater interrogation distance than with previously known TAGs, and has an increased bit capacity. The device should enable free programming that is simple to perform. The invention proposes a surface transducer device having the features according to claim 1. Advantageous developments are described in the subclaims. Surface-wave transducer device comprising the combination of a first transmitter device of the dispersive type and a second transmitter device of the non-dispersive type, comprising a multiplicity of n non-dispersive transducers which can be coded or are coded with an identification code.

Actuator utilizing piezoelectric transducer

Abstract: There is provided an actuator utilizing a piezoelectric transducer that is structured in small size by feeding the electrical power to the internal surface to the piezoelectric transducer formed in the cylindrical shape. The electrodes are formed to both front and rear surfaces of a sheet type piezoelectric element and this element is wound in the cylindrical shape. The cylindrical material is normalized under the predetermined temperature and a voltage is applied across the electrodes for the polarization purpose. An electrode terminal having the contactors is inserted to the internal surface of the piezoelectric transducer formed in the cylindrical shape and the contactors are placed in contact with the electrodes exposed at the internal surface of the cylindrical shape for the purpose of power feeding.

Fast leaky surface acoustic waves on lithium niobate and lithium tantalate

Abstract: The singularities of effective permittivity function for lithium niobate and tantalate are located in supersonic region and can be explicitly determined when a curved cut line is drawn from the longitudinal branch point. The singularities correspond to supersonic fast leaky waves. The supersonic fast leaky SAW exists on the ordinary YZ cut of lithium niobate. Due to the slowing and trapping effects under large mass and stress periodical loading these waves can be effectively generated by surface sources. Calculations of admittance characteristics of an infinitely long interdigital transducer show that the quality factor at resonant and antiresonant frequencies can attain several thousand of magnitude. The dispersion curves of these waves propagating in short and open circuited periodical systems of metal electrodes have been calculated.

Surface acoustic wave optical element

Abstract: PROBLEM TO BE SOLVED: To provide a surface acoustic wave optical element which ensures higher energy efficiency SOLUTION: A generator 12 for generating surface acoustic wave, a transducer 13 and a reflector 15 are formed on a piezoelectric film 11a of a substrate, while a transducer 14 and a reflector 16 are formed on a piezoelectric film 11b An AC voltage of E1=E0sinωt is applied to a comb-type electrode 12a, while an AC voltage of E2=E0cosωt to a comb-type electrode 12b, forming the generator 12 in order to excite the substrate 11 Thereby, the unidirectional surface acoustic wave W, traveling in the direction of arrow mark a (right side of the figure), is generated The surface acoustic wave W traveling in the direction of the arrow mark a is converted mechanically and electrically by the transducer 14, energy of such waves is collected as the electrical vibration, it is then circulated to the transducer 13 to re-excite the substrate 11 Optical elements (moving bodies) such as a lens, a polarizer or the like arranged in the space 17 on the substrate 11 can be moved with the surface acoustic wave generated on the substrate

Design optimization and experimental verification of wireless IDT based micro temperature sensor

Abstract: This paper presents the prediction and measurement of the phase response from a wireless surface acoustic wave (SAW) device for temperature sensing applications. This wireless sensor consists of two or more arrays of an interdigital transducer (IDT) and reflector pair with different IDT-reflector distances. Pulse modulated signals are transmitted from a remote reader system and their echoes are returned with different time delays due to the different IDT-reflector distances. Corresponding intermediate frequency signals are generated in a mixer and their phase differences are calibrated to temperature values. Using the coupled-mode theory of SAWs, the phase characteristic relative to temperature was examined. The effect of the relative distances between the two reflector arrays is demonstrated. The influence of the phase reversal location, which produces multiple temperature values for a given phase difference, is also discussed and a simple solution is illustrated. This sensor is coupled with a small planar antenna, which will be well suited for applications that require passive and conformal sensors.

Modeling and electrode optimization for torsional IDE piezoceramics

Abstract: Conventionally electroded surface-bonded piezoceramic elements are incapable of controlling torsional motions because the in- plane isotropic actuation strain is orthogonal to the surface shear strain pattern associated with torsional deformations. For devices with in-plane orthotropic properties, however, such as those with interdigital electrodes (IDE), sensing and controlling torsion is possible, allowing damping by passive or active means. An electromechanical model is developed for orthotropic piezoceramic devices bonded to the surfaces of beams or tubes in torsion; expressions for mechanical compliance, actuator authority, electromechanical coupling, and passively attainable damping for the combined system are derived in terms of geometric and material parameters and orientations. Optimization of the actuator orientation and geometry is addressed, with specific attention to the width, spacing, and angle of interdigital electrodes. Experimentally determined damping ratios are presented for torsional IDE piezoceramic devices with passive shunts, along with considerations for future improvements.

Method of making surface acoustic wave device

Abstract: A method of making surface acoustic wave device includes a piezoelectric substrate, a first surface acoustic wave element having at least one interdigital transducer on the piezoelectric substrate, a second surface acoustic wave element having at least one interdigital transducer which is provided on the piezoelectric substrate. The at least one interdigital transducer of the second surface acoustic wave element has a thickness that is different from the interdigital transducer of the first surface acoustic wave element, and the second surface acoustic wave element has a frequency characteristic that is different from that of the first surface acoustic wave element. An insulating film is applied to the first and second surface acoustic wave elements. A thickness of the insulating film at a region on the first surface acoustic wave element is different from the thickness of a region on the second surface acoustic wave.

Automatic computer-aided design of SAW filters using slanted finger interdigital transducers

Abstract: This paper describes a design procedure for surface acoustic wave (SAW) filters using slanted finger interdigital transducers (SFIT) that are suitable for mid-band or wideband applications. The SFITs cannot represent the impulse response directly, in contrast to apodized IDTs. A design method for SFITs based on a building-block approach in the frequency domain is described. An automatic computer-aided design tool for SFIT filters has been achieved. The SFIT filters can be designed using a withdrawal weighting for stop-band responses, an aperture weighting for pass-band amplitude responses, and a distance weighting for pass-band phase responses. In addition, a SFIT pattern for photo mask can be automatically designed using this tool. Using this tool, an SFIT filter with a relative bandwidth of 15% was designed on an x-cut 112y-direction LiTaO/sub 3/ substrate.

Impedance matching transducers

Abstract: The present invention provides exemplary transducer elements, transducer packages and methods of making same. One exemplary transducer element (10) has first and second transducer surfaces (14, 20) and a plurality of tapered pillars (16) that comprise piezoelectric material and extend between the first and second transducer surfaces. At least one of the pillars (16) has a first cross-sectional area at the first tranducer surface (14) that is larger than a second cross-sectional area at the second transducer surface (20). Hence, the transducer has a lower acoustic impedance at the second surface than at the first surface.

Method for exciting lamb waves in a plate, in particular a container wall, and an apparatus for carrying out the method and for receiving the excited lamb waves

Abstract: In order to excite Lamb waves in a plate (8) or container wall (8), it is proposed that an IDT transducer (interdigital transducer), which is known per se and comprises a layer (1) composed of piezoelectric material, and on one of whose surfaces two electrodes (2, 3) which engage in one another like fingers are applied, be acoustically coupled to the plate (8) or container wall (8) by means of the surface facing away from the electrodes (2, 3) If a radio-frequency AC voltage is applied to the connections (6, 7) of the electrodes (2, 3), then a thickness vibration is initiated in the piezoelectric layer (1) If the speed of propagation or speed of sound of the longitudinal waves which result in this thickness vibration in the piezoelectric layer (1) is matched to the phase velocity with which an so mode Lamb wave propagates in the material of the plate (8) or of the container wall (8), then only so mode Lamb waves are initiated by the resonance effect in the plate (8) or container wall (8), by virtue of the acoustic coupling between the piezoelectric layer (1) and the plate (8) or container wall (8) The matching process can be carried out by selecting the distance (D) between the fingers (4, 5) of the electrodes (2, 3) such that this distance (D) is equal to half the wavelength λ/2 of the thickness vibration to be initiated in the piezoelectric layer (1)

Saw resonator, composite saw filter, and saw filter

Abstract: A surface acoustic wave resonator includes a piezoelectric substrate and an interdigital transducer (10) on the piezoelectric substrate. The interdigital transducer includes first (10a) and second (10b) comb-shaped electrodes having one or more electrode fingers which are interdigitated with each other. When the first comb-shaped electrode (10a) is connected to a positive potential, the second comb-shaped electrode (10b) is connected to a negative potential, and the electrode finger connected to the positive potential and the electrode finger connected to the negative potential are reversed in at least one pair of the electrode fingers in an area where electrode fingers connected to the positive potential and electrode fingers connected to the negative potential are alternately arranged in the direction of surface-wave propagation.

Surface acoustic wave resonator, surface acoustic wave device, and communication device using shear horizontal waves

Abstract: A surface acoustic wave resonator includes a piezoelectric substrate and an interdigital transducer disposed on the piezoelectric substrate and made of a metal or an alloy having a higher specific weight than that of the piezoelectric material of the piezoelectric substrate so as to generate shear horizontal waves. The interdigital transducer includes a plurality of electrode fingers. A ratio of the electrode finger width relative to the electrode finger width plus the space between adjacent electrode fingers is about 0.55 to about 0.85.

Surface acoustic wave actuator, and magnetic disk device and optical disk device using the same

Abstract: A surface acoustic wave actuator is disclosed which includes unidirectional interdigital transducers disposed on both sides of a vibrator and an electrical combiner. One of the unidirectional interdigital transducers and external power supply are connected to an input port, and the other unidirectional interdigital transducer is connected to an output port of the electrical combiner. The electrical combiner combines input energy from an external power supply and surface acoustic wave energy is electrically converted by one of the unidirectional interdigital transducers, and input to the other unidirectional interdigital transducer. Surface acoustic waves excited by the other unidirectional interdigital transducer propagates on a vibrator, and is input to the other unidirectional interdigital transducer again after passing one unidirectional interdigital transducer and the electrical combiner. A relative movement member is pressed against the vibrator for generating driving force via a friction force so that the relative movement member implements relative movement to the vibrator.

Recessed reflector single phase unidirectional transducer

Abstract: The invention relates to a new family of surface acoustic wave single-phase unidirectional transducers (SPUDTs) by using M uniform width, uniformly spaced, single-level interdigitated electrodes lying on a uniform grid of a piezoelectric substrate where unidirectionality is achieved by selectively etching reflective structures into the substrate either in the spaces located between adjacent electrodes or under selected electrodes of the transducer. A SAW filter, resonator or delay line can also be formed by fabricating two such transducers on a single substrate, each having surface acoustic waves radiating towards the other.

Surface acoustic wave filter and branching filter utilizing it

Abstract: Disclosed is a surface acoustic wave filter having a first serial-arm SAW resonator coupled to an input terminal and a first dual-mode SAW resonator coupled between the first serial-arm SAW resonator and an output terminal, wherein the first dual-mode SAW resonator includes first to third comb-shaped interdigital transducers, the second comb-shaped interdigital transducer is arranged between the first and third comb-shaped interdigital transducers and also coupled between the first serial-arm SAW resonator and the ground potential, and each of the first and third comb-shaped interdigital transducers is coupled between the ground potential and the output terminal. Also disclosed is a branching filter utilizing the surface acoustic wave filter.

Edge reflection type surface acoustic wave device with grooves or steps at the reflection edges

Abstract: An edge reflection type surface acoustic wave device utilizes a Shear Horizontal type surface acoustic wave and includes a surface acoustic wave substrate, and at least two interdigital transducers provided on one main surface of the surface acoustic wave substrate. First and second grooves are formed on the opposite ends in the surface acoustic wave propagation direction of the area where the interdigital transducer is provided. The first and second grooves extend from the one main surface of the surface acoustic wave substrate toward the other main surface thereof without reaching the other main surface. The grooves extend substantially perpendicularly to the surface acoustic wave propagation direction so as to define first and second edges for reflecting the surface acoustic wave. The first and second edges are defined by the inner sideively. walls of the first and second grooves, respectively.

Saw resonator filter and duplexer utilizing SH waves, substrate edge reflection, and sub-interdigital transducer portions

Abstract: A SAW resonator filter which generates Shear Horizontal type surface acoustic waves includes a piezoelectric substrate, and first and second resonators arranged on the piezoelectric substrate. The first and second resonators include first and second interdigital transducers having electrode fingers, respectively. The first and second interdigital transducers are acoustically coupled to form a filter, and are divided into a plurality of sub-interdigital transducer portions, respectively. By dividing the interdigital transducers to have multiple sub-IDT portions, the effective electromechanical coupling coefficient is reduced, thereby enabling the bandwidth to be made narrower. Further, the improvement in the electrode structure allows for the filter to use a piezoelectric substrate having excellent temperature characteristics, so that it is possible to achieve a SAW resonator filter having a narrow bandwidth and superior temperature characteristics. Moreover, when an edge reflection type SAW resonator filter using SH-type surface acoustic waves is made, it is possible to provide a compact bandpass filter having low insertion loss and excellent selectability.

Surface acoustic wave device capable of suppressing spurious response due to non-harmonic higher-order modes

Abstract: A surface acoustic wave device which includes a piezoelectric substrate, and an interdigital transducer formed on a planar surface of the piezoelectric substrate, and having first and second bus bars, a first plurality of electrode fingers connected to the first bus bar, and a second plurality of electrode fingers connected to the second bus bar. The first and second plurality of electrode fingers of the interdigital transducer have an electrode cross region in which the first and second plurality of electrode fingers are arranged alternatively. Each boundary between the first and second bus bars and a grating region of the first and second plurality of electrode fingers is arranged such that the boundary is not substantially parallel, with a transmission direction of surface acoustic waves excited by the interdigital transducer.

Ultrasound-signal radiating device

Abstract: An ultrasound-signal radiating device comprises a piezoelectric substrate, a first input interdigital transducer, a second input interdigital transducer, an output interdigital transducer, a cap, an amplifier, and a modulator with an input terminal. All the interdigital transducers are formed on one end surface of the piezoelectric substrate. The cap is mounted on a surface part of the other end surface of the piezoelectric substrate. If an input electric signal is applied to the first input interdigital transducer, a non-leaky elastic wave is excited in the piezoelectric substrate owing to the existence of the cap. The non-leaky elastic wave is detected at the output interdigital transducer as a delayed electric signal, which is amplified via the amplifier. A signal part of an amplified electric signal is fed back to the first input interdigital transducer, again. A remaining signal part, as a carrier signal, of the amplified electric signal is transmitted to the modulator, where an amplitude of the carrier signal is modulated according to an input message-signal applied from the input terminal. Thus, an AM signal is generated, and then, applied to the second input interdigital transducer. In this time, a leaky elastic wave is excited in the piezoelectric substrate, and radiated effectively in the form of a longitudinal wave into a liquid kept in contact with a remaining surface part of the other end surface of the piezoelectric substrate.

Surface acoustic wave device and method of producing the same

Abstract: A surface acoustic wave device includes a piezoelectric substrate, a first surface acoustic wave element having at least one interdigital transducer on the piezoelectric substrate, a second surface acoustic wave element having at least one interdigital transducer which is provided on the piezoelectric substrate. The at least one interdigital transducer of the second surface acoustic wave element has a thickness that is different from the interdigital transducer of the first surface acoustic wave element, and the second surface acoustic wave element has a frequency characteristic that is different from that of the first surface acoustic wave element. An insulating film is applied to the first and second surface acoustic wave elements. A thickness of the insulating film at a region on the first surface acoustic wave element is different from the thickness of a region on the second surface acoustic wave.

Surface acoustic wave (SAW) device

Abstract: A surface acoustic wave device includes a piezoelectric substrate (2), and an interdigital transducer (3) provided on the piezoelectric substrate (2), wherein the piezoelectric substrate (2) includes at least two piezoelectric ceramic layers made of a polycrystalline material. The at least two piezoelectric ceramic layers are stacked so that electrical characteristics and mechanical characteristics thereof vary in a direction that is substantially perpendicular to a surface of the piezoelectric substrate (2) upon which the at least two ceramic piezoelectric layers are stacked.

Electrically tunable YBa2Cu3Oy resonators using interdigital electrodes and dielectric film

Abstract: We have fabricated electrically tunable YBa2Cu3Oy (YBCO) resonators using interdigital electrodes and a dielectric film, and have investigated their tuning capabilities. The tuning section, which consists of an SrTiO3 (STO) dielectric film and SrRuO3 (SRO) interdigital electrodes, was stacked on a half-wavelength microstrip line resonator. The change of the dielectric constant of the STO film by applying a bias voltage between the electrodes leads to the tunability. The range of frequency modulation and the quality factor were 10 MHz (0.21%) and 2100 at 40 K, 75 kV/cm, respectively. This tuning method has an advantage over conventional methods in that individual filter elements can be tuned independently and a high quality factor is expected.

Composite saw filter with a saw filter and a withdrawal weighted or electrode reversed saw resonator

Abstract: A surface acoustic wave resonator includes a piezoelectric substrate and an interdigital transducer on the piezoelectric substrate. The interdigital transducer includes first and second comb-shaped electrodes having one or more electrode fingers which are interdigitated with each other. When the first comb-shaped electrode is connected to a positive potential, the second comb-shaped electrode is connected to a negative potential, and the electrode finger connected to the positive potential and the electrode finger connected to the negative potential are reversed in at least one pair of the electrode fingers in an area where electrode fingers connected to the positive potential and electrode fingers connected to the negative potential are alternately arranged in the direction of surface-wave propagation.

Saw device and communication device using saw device

Abstract: A SAW device comprises input/output interdigital transducer (IDT) electrodes (11, 12) provided on piezoelectric substrates (10), a first reflector electrode (13) following the input IDT electrode (11), and a second reflector electrode (14) preceding the output IDT electrode (12). The device satisfies the following inequality (1) to provide preferable characteristics in a pass band: 2( theta - 5) (D / L)

Surface acoustic wave device having an interdigital transducer provided on a main region of a piezoelectric substrate

Abstract: A surface acoustic wave device includes a piezoelectric substrate having a pair of substrate edges and an upper surface therebetween. The piezoelectric substrate has at least one inner edge which is in contact with a main region and extends from the upper surface toward a bottom surface of the piezoelectric substrate inside one of the substrate edges. An interdigital transducer is provided on the main region of the piezoelectric substrate such that a SH type surface acoustic wave excited by the interdigital transducer and having a wavelength of λ is reflected by the at least one inner edge. A distance L between the at least one inner edge and the corresponding one of the substrate edges is substantially equal to about 8λ or less.