Showing papers on "Interdigital transducer published in 2002"

Piezoelectric electroacoustic transducer

Abstract: A piezoelectric electroacoustic transducer eliminates the need for the interconnection between main surface electrodes and internal electrodes, and is capable of constructing a bimorph diaphragm using a simple connection structure. The piezoelectric electroacoustic transducer includes a laminated body formed by laminating two or three piezoelectric ceramic layers, main surface electrodes each provided on the top and bottom main surfaces, and an internal electrode provided between any adjacent two piezoelectric ceramic layers. In the piezoelectric electroacoustic transducer, all ceramic layers are polarized in the same direction with respect to the thickness direction, and by applying an alternating voltage across the main surface electrodes and the internal electrode, the laminated body generates a bending vibration in its entirety.

Surface acoustic wave filter device

Abstract: A small-sized surface acoustic wave filter device having favorable filter characteristics includes a transmission-side surface acoustic wave filter chip including a ladder surface acoustic wave filter unit located on a piezoelectric substrate. The ladder surface acoustic wave filter unit includes a series arm connected between an input pad and an output pad and a plurality of resonators and including at least one first resonator connected to the input pad or the output pad. A die-attach surface is provided with an inductor connected to the first resonator. The inductor is arranged such that at least a portion thereof faces the first resonator and does not face any of the plurality of resonators and other than the first resonator.

Surface acoustic wave apparatus and communication apparatus

Abstract: A longitudinally-coupled-resonator-type surface acoustic wave filter includes three interdigital transducers provided on a piezoelectric substrate in the direction in which surface acoustic waves propagate An interdigital transducer disposed at the approximate center among the three interdigital transducers of the longitudinally-coupled-resonator-type surface acoustic wave filter is divided into two parts substantially symmetrically in the propagation direction of the surface acoustic waves and the two parts are connected to balanced signal terminals, respectively Left and right interdigital transducers of which the polarities are inverted relative to each other are connected to an unbalanced signal terminal to provide a balanced-to-unbalanced conversion function A reactance component provided on the piezoelectric substrate, inside a package, or outside the package is connected to either of the balanced signal terminals

Surface acoustic wave resonator and surface acoustic wave filter

Abstract: A surface acoustic wave resonator includes a piezoelectric substrate, and a SAW resonator having an interdigital transducer. The interdigital transducer satisfies 0.15L≦W≦0.45L where W is the total of widths of all electrode fingers that form the interdigital transducer, and L is a length of the said interdigital transducer in a direction of SAW propagation.

Electro-optic optical elements

Abstract: Electro-optic elements are formed in metal oxide films, such as lithium niobate, on a substrate such as lithium niobate for utilization in electro-optical devices. The electro-optic elements include trenches in the lithium niobate selected to improve the performance of the device. Traveling wave modulators may be formed with a waveguide having first and second arms, electrodes over the lithium niobate layer, and trenches formed in the layer to focus the electric field in the waveguide, resulting in improved modulator performance.

Evaluation of a novel surface acoustic wave gyroscope

Abstract: A novel type of gyroscope sensor using metal dot arrays on the surface of a surface acoustic wave (SAW) device has recently been independently proposed. In this paper, we report experimental trials of several devices fabricated to evaluate the effects described and also an order-of-magnitude estimate of the sensitivity to be expected. The conclusions are that this device is extremely insensitive as currently proposed.

Surface acoustic wave device

Abstract: PROBLEM TO BE SOLVED: To improve reflectivity of a reflector and to obtain the small reflector by suppressing reflected waves losses due to mode conversion in bulk waves, etc SOLUTION: A surface acoustic wave device is provided having a piezoelectric baseboard 10, an interdigital transducer (1a and 1b) formed on the piezoelectric baseboard 10 and the reflector consisting of multiple metal strip electrodes (2a, 2c, 3a and 3d) which are formed on the baseboard 10; and the device is constituted, such that the film thickness of a metal strip constituting the reflector is made thicker, the larger the reflectivity becomes, going away from the interdigital transducer

Very small IF resonator filters using reflection of shear horizontal wave at free edges of substrate

Abstract: A conventional surface acoustic wave (SAW) resonator filter requires reflectors consisting of numerous grating fingers on both sides of interdigital transducers (IDTs). On the contrary, it is considered that small-sized and low loss resonator filters without reflectors consisting of grating fingers can be realized by exploiting this characteristic of the shear horizontal (SH) wave or the Bleustein-Gulyaev-Shimizu (BGS) wave. There are two types of resonator filters: transversely coupled and longitudinally coupled. No transversely coupled filters (neither conventional nor edge-reflection) using the SH wave on a single-crystal substrate have been realized until now, because two transverse modes (symmetrical and asymmetrical modes) are not easily coupled. However, the authors have realized small low loss transversely coupled resonator filters in the range of 25 to 52 MHz using edge reflections of the BGS wave on piezoelectric ceramic (PZT: Pb(Zr,Ti)O/sub 3/) substrates for the first time by developing methods by which the two transverse modes could be coupled. Also the authors have realized small low loss longitudinally coupled resonator filters in the range of 40 to 190 MHz using edge reflection of BGS or SH waves on PZT or 36/spl deg/-rotated-Y X-propagation LiTaO/sub 3/ substrates for the first time. Despite being IF filters, their package (3/spl times/3/spl times/1.03 mm/sup 3/) sizes are as small as those of RF SAW filters.

Modelling of Lamb Waves in Composite Laminated Plates Excited by Interdigital Transducers

Abstract: The technique of permanently attaching interdigital transducers (IDT) to either flat or curved structural surfaces to excite single Lamb wave mode has demonstrated great potential for quantitative non-destructive evaluation and smart materials design, In this paper, the acoustic wave field in a composite laminated plate excited by an IDT is investigated. On the basis of discrete layer theory and a multiple integral transform method, an analytical-numerical approach is developed to evaluate the surface velocity response of the plate due to the IDTs excitation. In this approach, the frequency spectrum and wave number spectrum of the output of IDT are obtained directly. The corresponding time domain results are calculated by applying a standard inverse fast Fourier transformation technique. Numerical examples are presented to validate the developed method and show the ability of mode selection and isolation. A new effective way of transfer function estimation and interpretation is presented by considering the input wave number spectrum in addition to the commonly used input frequency spectrum. The new approach enables the simple physical evaluation of the influences of IDT geometrical features such as electrode finger widths and overall dimension and excitation signal properties on the input-output characteristics of IDT. Finally, considering the convenience of Mindlin plate wave theory in numerical computations as well as theoretical analysis, the validity is examined of using this approximate theory to design IDT for the excitation of the first and second anti-symmetric Lamb modes. (C) 2002 Elsevier Science Ltd. All rights reserved.

Surface acoustic wave device with divided interdigital transducers

Abstract: A surface acoustic wave device includes an input interdigital transducer and an output interdigital transducer, disposed on a surface acoustic wave propagation path of a piezoelectric substrate, wherein when an aperture length of an electrode finger of the input or output interdigital transducer is denoted by X, the output or input interdigital transducer has two divided interdigital transducers having the electrode finger in which each aperture length is denoted by substantially X/2, wherein the two divided interdigital transducers are serial-connected, and the electrodes of the respective electrode fingers are led from the two divided interdigital transducers, and are disposed so that two output and input signals connected to a balance terminal pair have a different phase at 180°.

Simulation of short LSAW transducers including electrode mass loading and finite finger resistance

Abstract: The theory for the 2-D numerical analysis of acoustic wave generation from finite length leaky surface acoustic wave (LSAW) transducer structures is presented. The mass loading of the electrodes is incorporated through the use of the finite element method (FEM). The substrate is modeled using both analytical and numerical means. The advantages of this simulation are twofold. First, it is capable of extracting the individual bulk wave conductances from the overall conductance of a given device. At large distances from the transducer, the angular distribution of power radiated relative to the substrate surface can then be calculated for each of the three possible bulk wave polarizations. The second advantage of the simulation is that the effect of finite electrode resistance is included through the use of a series equivalent resistance for each electrode in the structure. Once the resistance for each electrode in the structure has been determined, the overall effect on the device admittance is modeled by applying a constrained minimization process to the electrical boundary conditions of the transducer. To conclude the paper, the simulation will be compared against the experimental admittance of a 37-finger uniform transducer with a metallization ratio of 0.5 on 42/spl deg/ LiTaO/sub 3/. The agreement between theory and experiment is excellent.

Surface acoustic wave element, surface acoustic wave device using the same, and method for manufacturing surface acoustic wave element and surface acoustic wave device

Abstract: A surface acoustic wave device includes a surface acoustic wave element, a packaging case, and a packaging electrode. The surface acoustic wave element has a piezoelectric substrate, an interdigital transducer, an electrode pad, an intermediate electrode, an upper electrode, and a bump electrode. The intermediate electrode is preferably made of NiCr including about 15 to about 30 weight percent of Cr. The electrode pad and upper electrode are made of Al. The bump electrode is press-bonded to the packaging electrode with an ultrasonic wave or heat applied to the bump electrode. The resulting surface acoustic wave device has excellent characteristics and the surface acoustic wave element is not removed or peeled from the packaging case during a drop test.

Propagation of surface acoustic waves in a GaAs/AlAs/GaAs heterostructure and micro-beams

Abstract: The dispersion of the Rayleigh wave in a strain-unrelaxed GaAs/AlAs/GaAs heterostructure is evaluated. We determine the wavelengths at which the velocity of surface acoustic waves (SAWs) is maximum or comparable to that in GaAs. The information is utilized to design interdigital transducers to investigate the SAW transmission properties when GaAs micro-beams are realized in the SAW propagation path by selectively etching the buried AlAs layer. A frequency shift as well as an attenuation of the SAW transmission peak is observed for certain SAW wavelengths within the range of the enhanced SAW velocity in the unpatterned heterostructure.

Optimization of broadband uniform beam profile interdigital transducers weighted by assignment of electrode polarities

Abstract: This paper considers techniques for optimizing surface acoustic wave (SAW) interdigital transducers (IDTs) with uniform electrode length (no apodization). Unlike other optimization techniques developed for this type of IDT, the algorithms proposed here choose the best electrode structure on the basis of how well it meets the specifications, not in the time domain, but in the frequency domain directly. In the first step of the optimization, a periodic transducer is synthesized. The weighting technique for providing a desired frequency response involves assigning polarities to the individual electrodes. The next step of the IDT selectivity improvement is the optimization of the electrode positions. In addition, the second algorithm can synthesize specified nonsymmetric frequency responses. A set of IDTs and SAW filters with bandwidths of 1 to 14% has been designed using this algorithm.

SSBW to PSAW conversion in SAW devices using heavy mechanical loading

Abstract: The development of efficient computation tools based on mixed analytical and numerical calculation approaches allows precise descriptions and characterizations of surface acoustic waves (SAW) propagation, taking into account realistic electrical and mechanical boundary conditions. As an example, suppression of the leaky SAW, also called pseudo SAW (PSAW), attenuation has been predicted using such tools allowing to explain experimental occurrences for SAW devices on YX cut lithium niobate and lithium tantalate with thick aluminum strip gratings (6% < h//spl lambda/ < 10%). In this work, such a theoretical model is used to analyze the evolution of surface waves on standard YX lithium tantalate cuts versus aluminum strip height. It is shown that the surface skimming bulk wave (SSBW), which accompanies the pseudo SAW on such crystal orientations, may be trapped by the grating, exhibiting then a second pseudo SAW behavior when close to the Bragg condition. A device has been designed and fabricated to check these theoretical predictions. The experimental evidence of the existence of the phenomenon allows one to discuss its consequences on more classical devices built on (Y + 36/spl deg/, X) LiTaO/sub 3/ substrates.

Shaped piezoelectric composite array

Abstract: An underwater acoustic transducer includes a set of formed substrates of piezoelectric polymer composite, the formed substrates having at least a first and second surface. Conductive electrodes are deposited on the first and second sides of the formed substrates. One surface of the substrate is bonded to an acoustically absorptive backing material. Either surface can be made to conform to a singly or doubly curved geometry. Electrodes deposited on these substrates may be continuous to form a single transducer element, or segmented to form sub-arrays of transducer elements.

Saw device and method for manufacture thereof

Abstract: A surface acoustic wave (SAW) device having improved moisture resistance is provided The device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode on a first surface of the piezoelectric substrate, and a resin coating for covering the IDT electrode After a piece of resin material of the resin coating is dipped in an amount of pure water as solvent having a mass as 10 times great as the piece of resin material at 120° C under 2 atom pressure for twenty hours, a concentration of chlorine ion in the solvent is not higher than 50 ppm

Electromechanical transducer and method for transforming energies

Abstract: A electromechanical transducer comprising at least one transducer element (2, 2a) which has a multilayer structure comprising at least two layers such that the transducer element is capable of changing its thickness. The transducer element (2a, 2b) allows air to flow inside the transducer element (2, 2a, 2b) in the direction of thickness thereof and inside and out of the transducer element (2a, 2b) through at least one surface of the transducer element (2a, 2b) in the direction of thickness of the transducer element (2a, 2b). The transducer element can be used e.g. for transforming energy from mechanical energy into electric energy and/or vice versa.

An empirical method for obtaining the harmonic response coefficients of a SAW interdigital transducer

Abstract: An empirical delta-function model is applied to obtain the harmonic response coefficients for solid-electrode, split-electrode, and "three-finger" surface acoustic wave (SAW) interdigital transducers (IDTs). Good agreement is obtained between harmonic coefficients and polarities obtained by other investigators who used rigorous analytical methods. In principle, this empirical model - employing a complex summation of idealized transverse and longitudinal E-fields under, and between, adjacent electrodes - should be applicable to modeling the fundamental and harmonic responses of SAW and leaky-SAW IDTs.

Tire pressure and temperature sensor comprises a hermetically sealed housing with a membrane, piezoelectric support, interdigital transducer and measurement and reference reflectors

Abstract: Passive pressure and temperature sensor has a radio interface with which it can be interrogated by a control unit. Sensor has a hermetically sealed housing (10) that is filled with a defined gas volume and has a membrane (8) with a surface wave structure that is connected to an antenna (3). A piezoelectric support (1) and an interdigital transducer (4) are used with measurement (6, 7) and reference (5) reflectors. An Independent claim is made for a measurement arrangement for dynamic measurement of temperature and pressure within a motor vehicle tire.

Surface acoustic wave device and communications apparatus using the same

Abstract: The invention provides an in-plane rotational ST-cut SAW resonator that is formed of an in-plane rotational ST-cut crystal plate having Eulerian angles of (0°, 113° to 135°, and ±(40° to 49°)). The in-plane rotational ST-cut SAW resonator can include an interdigital transducer (IDT) electrode for exciting a Rayleigh wave on the main surface. The ratio Lt/Pt of the electrode width Lt and the interelectrode pitch Pt of the IDT electrode is 0.5 or more and 0.65 or less. Accordingly, a reduction in the fluctuation in resonance frequency relative to the variations in an IDT electrode of a surface acoustic wave device by using the in-plane rotated ST-cut crystal plate around the Z′-axis can be achieved.

Electrical characterization of plate piezoelectric transducers bonded to a finite substrate.

Abstract: This article presents a new technique for characterizing piezoelectric transducers attached to a finite substrate. It consists of determining the impedance of the transducer cleared of the effects caused by finite dimensions of the substrate. This technique is validated by comparison with measurements on a transducer mounted on an effectively half-infinite substrate. It is applied for the electrical matching of a lithium niobate plate transducer bonded to a fused quartz rod.

Interdigital transducer surface acoustic wave filter and radio communication apparatus

Abstract: An interdigital transducer has one-wavelength basic units of a single phase unidirectional transducer a plurality of each having three electrode fingers within one wavelength; and a plurality of one-wavelength basic units of a bidirectional electrode each having four electrode fingers within the one wavelength, wherein the one-wavelength basic units are properly arranged according to a desired filter characteristic, and one of the three electrode fingers of each one-wavelength basic unit of the single phase unidirectional transducer is wider than the two other electrode fingers, and of the four electrode fingers of each one-wavelength basic unit of the bidirectional electrode, one pair of two fingers is interdigitated to the other pair of two fingers, and an adjustment section is provided between the one-wavelength basic units of the single phase unidirectional transducer and the one-wavelength basic units of the bidirectional electrode.

Surface acoustic wave filter and communications apparatus using the same

Abstract: A surface acoustic wave filter has a piezoelectric substrate and at least two interdigital transducer electrodes on the piezoelectric substrate, wherein at least one of the interdigital transducer electrodes includes a unidirectional electrode and bidirectional electrode, and the length λd of a basic cell of the unidirectional electrode is longer than the length λs of a basic cell of the bidirectional electrode.

Surface acoustic wave device and method for mfg. same

Abstract: A surface acoustic wave device includes a piezoelectric substrate, and at least one interdigital transducer disposed thereon which is made of a metal or an alloy that is heavier than Al. The acoustic velocity distribution of surface acoustic waves in the extending direction of electrode fingers of the at least one interdigital transducer is not greater than about 276 ppm, thereby effectively suppressing considerable ripples, which are noticeably found in the group delay time characteristic in particular, within the bandpass area.