Showing papers on "Interdigital transducer published in 1993"

Surface acoustic wave (SAW) chemical multi-sensor array

Abstract: A sensor for chemical vapor detection using a surface acoustic wave (SAW) ray that provides a means for simultaneously detecting several chemical agents. The sensor has a piezoelectric substrate and a bidirectional surface acoustic wave transducer on the substrate. Also on the substrate are several pairs of identical acoustic sensing and reference channels each on opposite sides of the transducer in a mirror image fashion. Each channel pair has a thin film capable of absorbing a chemical vapor to be monitored and a metallic surface acoustic wave grating reflector capable of receiving and reflecting surface acoustic waves through the thin film and back to the transducer. An acoustic absorber separates each channel. The reference channels are protected from ambient conditions while the sensing channels are exposed to such conditions. An RF signal is applied to the transducer causing the propagation of an acoustic signal into each of the sensing channels and reference channels. Output signals from the transducer are then detected. The array is preferably in a miniature configuration which is suitable for wearing on a person's wrist or arm.

1.5 GHz Low-Loss Surface Acoustic Wave Filter Using ZnO/Sapphire Substrate

Abstract: A 15 GHz range low insertion loss surface acoustic wave (SAW) filter has been developed using a ZnO/sapphire substrate and IIDT-type electrodes with two external reflectors This filter had an insertion loss of 13 dB, stop-band attenuation of greater than 30 dB and matching impedance of 50 Ω pure resistivity without external matching networks This filter has the smallest insertion loss of all transverse-type GHz-range SAW filters reported previously and it is suitable for use as a RF-stage filter for future 15 GHz range Japanese digital cellular systems

Ultrasonic touch system

Abstract: An ultrasonic touch system including a substrate and at least an ultrasonic transducing system on one end surface (Z1) of the substrate. The ultrasonic transducing system comprises at least an interdigital transducer (P) and at least an interdigital transducer (Q) corresponding to the interdigital transducer (P). An electric signal having a frequency approximately corresponding to the interdigital periodicity of the interdigital transducer (P) is applied to the interdigital transducer (P), causing the acoustic wave on the end surface (Z1) with a high efficiency, the acoustic wave having a wavelength approximately equal to the interdigital periodicity of the interdigital transducer (P). At this time, an electric signal having a frequency approximately corresponding to the wavelength of the acoustic wave generated on the end surface (Z1) is detected at the interdigital transducer (Q). When touching with a finger or other things on a part of the propagation medium of the acoustic wave on the end surface (Z1), the electric signal detected at the interdigital transducer (Q) is decreased. A touch on the substrate by a finger or other things is accordingly detected with a high sensitivity and a quick response time under operation with low power consumption and low voltage.

Hybrid ultrasonic transducer

Abstract: An ultrasonic transducer employed for both transmitting ultrasonic acoustic energy into an immersion medium and for detecting acoustic energy reflected from an object under examination is provided, the transducer having a hybrid transmitter and receiver in which a ceramic piezoelectric material is used to construct a first piezoelectric element for transmitting the acoustic energy, and a polymer piezoelectric material is used to fabricate a second piezoelectric element for receiving the reflected acoustic energy. The hybrid ultrasonic transducer provides improved performance over prior transducers using only a single ceramic piezoelectric element, in that the good transmitting properties of the ceramic are preserved, while the better receiving properties of the polymer piezoelectric are used to improve the sensitivity of the transducer. The polymer piezoelectric has the further advantage of providing a closer match of acoustic impedance to the immersion fluid used in the evaluation of objects.

Surface acoustic wave device with interdigital transducers formed on a holding substrate thereof and a method of producing the same

Abstract: A surface acoustic wave device (31) includes: a holding substrate (1); a piezoelectric substrate (3); an interdigital transducer (4e-4d) formed on the holding substrate; and supports for holding said piezoelectric substrate on the holding substrate so that the interdigital transducer is evenly in contact with the piezoelectric substrate.

Interdigital capacitance and surface acoustic wave sensors

Abstract: The effects of the water content of sample vapors and the dielectric constant of a surface film on surface acoustic wave sensor performance are examined with respect to signal noise and the electrical properties of the interdigital transducer electrodes. The different mechanisms by which a surface film can affect SAW sensor response are reviewed before considering how the film dielectric constant may be important

Method for producing a surface acoustic wave device

Abstract: A surface acoustic wave device is so manufactured that it's reliability is increased and so that it is surface-mountable with no requirement for packaging. The surface acoustic wave device (20) has a pair of opposite interdigital electrodes (2a, 2b) and a piezoelectric member (4) in close contact with the interdigital electrodes (2a, 2b). A portion located between the pair of interdigital electrodes (2a, 2b) propagates surface acoustic waves. This device (20) is characterized by an air bridge (13) covering the portion of the piezoelectric member (4) for propagating surface acoustic waves and the pair of interdigital electrodes (2a, 2b). The air bridge (13), may be provided with an insulating film (14) which is not in contact with the piezoelectric member (4).

Characteristics of Zinc Oxide Films on Glass Substrates Deposited by RF-Mode Electron Cyclotron Resonance Sputtering System

Abstract: There are two types of electron cyclotron resonance (ECR) sputtering systems, DC-mode and RF-mode. In this paper, the properties of zinc oxide (ZnO) film deposited by an RF-mode ECR sputtering system capable of long-term stable deposition are investigated. It is confirmed for the first time that this system is capable of depositing a ZnO film having a sidewall structure without columnar or fibrous grains on an interdigital transducer (IDT)/glass substrate. The ZnO films so deposited were capable of driving the 1.1 GHz fundamental mode in a Rayleigh surface acoustic wave (SAW) without the large propagation loss at high frequencies of conventional ZnO films. Furthermore, ZnO films deposited by this system exhibited 1.7 dB lower insertion loss and a closer agreement between effective electromechanical coupling factors (keff) and the corresponding values calculated with the finite element method (FEM) in comparison with the films deposited by the DC-mode ECR sputtering system.

Method for manufacturing a surface acoustic wave device

Abstract: A surface acoustic wave device which can operate at a higher frequency range is produced by irradiation with a focused ion beam to produce a narrower electrode width and narrower spacing width between neighboring electrodes in contact with a piezoelectric body, without degrading the reliability of the device. The surface acoustic wave device includes a piezoelectric body 3 and interdigital electrodes 2a and 2b in close contact with the piezoelectric body 3 and formed by using the focused ion beam. In order to increase the frequency of the device, the piezoelectric body 3 may be formed on a substrate 1, for example of diamond.

Surface acoustic wave filter capable of widening a bandwidth

Abstract: In a surface acoustic wave filter utilizing at least two longitudinal modes, input and output interdigital transducers are mounted on a piezoelectric substrate so as to oppose each other. First and second grating reflectors are mounted on the piezoelectric substrate outside the input and the output interdigital transducers, respectively. Each of the input and the output interdigital transducers comprises a plurality of electrode digits which are equal to N in number. Each of the electrode digits is made of a metal material having a discontinuous impedance coefficient K related to acoustic impedance. The surface acoustic wave filter is structured so that a product of the number N and the discontinuous impedance coefficient K is not smaller than 0.55.

Generation and Bragg reflection of surface acoustic waves in nearly periodic system of elastic metal strips on piezoelectric half‐space

Abstract: Propagation of surface acoustic waves (SAW) in a periodic system of metal strips on an anisotropic piezoelectric substrate is analyzed using Green’s function for both the substrate and the system of strips. Appropriate approximations to these functions in spectral domain result not only in a uniform theory of SAW generation and Bragg scattering by strips that accounts for both the electric and elastic properties of the strips, but also in analytical solutions for dispersion relations and a scattering matrix for interdigital transducers. A new, comprehensive model for such transducers is proposed.

Electrostatic excitation and capacitive detection of flexural plate-waves

Abstract: A novel type of interdigital transducer has been developed for the excitation and detection of flexural plate-waves on very thin membranes. The launching transducer employs electrostatic forces for generating A0-mode flexural plate-waves. The receiving transducer detects the plate-waves via capacitive changes. The transducers operate without a piezoelectric substrate or layer. The proposed principle has been theoretically analyzed and experimentally tested. Results from the experiments confirm the theory and verify the principle. Additional improvement of the sensor output is achieved with a novel phase-locked-loop circuitry for electronic feedback. The absence of the piezoelectric layer facilitates the fabrication process of the sensor and allows extremely thin membranes to be developed with increased sensitivity for chemical and biological sensing. The design of moveable interdigital transducers has been demonstrated, with conceivable applications in position sensing, material characterization, and the theoretical investigation of flexural plate-waves.

X-cut crystal quartz acousto-optic modulator

Abstract: An acousto-optical laser modulator includes an X-cut crystal quartz block. A transducer, such as a piezoelectric device, is coupled to the block. An electrical signal provided to the transducer causes the transducer to vibrate. The vibrations propagate through the block as acoustic waves. A laser beam incident on the block may be refracted or diffracted by the acoustic waves. X-cut crystal quartz has various properties such as high thermal conductivity, low acoustic attenuation, high loss modulation efficiency, high drive power efficiency, and low angular sensitivity which make it well suited for applications in acousto-optical devices.

Method of fabricating a saw device

Abstract: A surface-acoustic-wave device comprises a substrate of a piezoelectric material for providing a passage of surface acoustic waves at an upper major surface of the substrate, a plurality of interdigital electrodes provided on the piezoelectric substrate in a row in correspondence to the passage of surface acoustic waves such that the electrodes are aligned in the propagating direction of the surface acoustic waves, each of the plurality of interdigital electrodes having a first part connected to a bonding pad on the substrate for external electric connection and having a plurality of finger electrodes extending parallel with each other in a direction crossing the propagating surface acoustic waves, and a second part separated from the first part and having a plurality of finger electrodes extending parallel with each other in a direction opposite to the direction of the finger electrodes of the first part. An interconnection pattern is provided on the surface of the substrate in correspondence to a region offset from the passage of the surface acoustic waves for connecting the second parts of adjacent interdigital electrodes with each other.

Growth and guided optical and surface acoustic wave properties of LiNbO 3 thin films

Abstract: Epitaxial LiNbO3 films were successfully grown on a-Al2O3(001), (012) and (110) and LiTaO3 (110 substrates) by RF magnetron sputtering. The optical guided wave propagation loss for those films was measured. The minimum optical propagation loss of the films was 6.47 dB/cm (TE0 mode) for the LiNbO3 film on LiTaO3 The theoretical calculation of the surface wave coupling coefficient predicted that the most simple and realistic configuration with its interdigital transducer on top of the LiNbO3 film and without the floating electrode gives the k2 values as high as 20.9% for the first mode and 7.4% for the 0th mode for the surface acoustic waves propagating in the [110] direction of the (110) LiNbO3 film on the (110) sapphire substrate, and values higher than 20% and 5.8% for those modes for the [12m0] propagation on the (100) LiNbO 3 film on the (012) sapphire substrate

Development of interdigitated acoustic wave transducers for biosensor applications

Abstract: The principle of operation, development and evaluation of two interdigitated acoustic wave transducers optimized for biosensor applications in liquid environments is presented. The first transducer is based on a plate mode wave approach whilst the second utilizes a novel evanescent surface acoustic wave design. Both transducer structures employ sensing from the bottom surface of a lithium niobate piezoelectric crystal. Acoustic wave mode selection from electrical performance data with respect to frequency response and phase shift spectrum of the transducers is discussed. A prerequisite for an acoustic biosensor is to demonstrate its suitability for operation in a wide range of liquid environments. Therefore, preliminary experimental results are presented detailing the effect of fluid viscosity on acoustic transducer response.

Multilayer piezoelectric ceramic actuator with interdigital internal electrodes

Abstract: A multilayer piezoelectric ceramic actuator with interdigital internal electrodes has been developed. The internal electrodes of this actuator are line electrodes which are printed on piezoelectric ceramic green sheets and stacked such that alternating electrode lines are displaced by one-half pitch. This actuator is displaced at right angles to the stacking direction due to the piezoelectric longitudinal effect. Therefore, it is possible to prepare a long ceramic actuator, which will be highly reliable in applications. In this work, we have obtained a displacement of 50 µm/DC350V and a generative force of 34.3 MPa for a 74-mm-long actuator. The reliability of this actuator is confirmed to have a long life of more than 1000 hours using applied voltage of DC350V at 25°C and 60%RH.

Admittance matrix of a surface acoustic wave interdigital transducer

Abstract: The admittance matrix of a surface acoustic wave interdigital transducer (IDT) is derived from the impulse response model and circuit theory. It is shown, that Y/sub 23/=Y/sub 13/ for a symmetrical IDT and Y/sub 23/-Y/sub 13/ for an antisymmetrical one. A simple algorithm for the input admittance calculation of apodized IDTs is given. The proposed algorithm is also capable of analyzing withdrawally weighted, withdrawally weighted and apodized, and unapodized IDTs. Calculations of an apodized IDT input admittance are compared with measurements. >

A simple equivalent circuit for interdigital transducers based on the coupled-mode approach

Abstract: The coupled-mode approach is a powerful tool for analyzing surface acoustic wave (SAW) periodic structures such as reflectors and interdigital transducers. The relations among the terminal quantities at two acoustical ports and one electrical port of an interdigital transducer (IDT) are derived from coupled-mode equations. A simple distributed-parameter equivalent circuit representing the entire IDT is proposed. A few examples of applications of this equivalent circuit to analysis of SAW devices are presented. >

Acoustic wave devices for controlling high frequency signals

Abstract: Devices are disclosed for controlling high frequency signals such as optic or electric signals by the generation of acoustic waves. The devices use certain bulk or surface-modified crystalline substrates which have a surface with a receiving area and an input (16) interdigital transducer deposited on the signal receiving area of the substrate surface which is suitable for connection to a source or signal (12) and for inverse piezoelectrically generating acoustic waves in the crystalline substrate (16). The crystalline substrates are of a material having a piezoelectric-elastic dielectric matrix capable of the generation of acoustic waves and for bulk substrates, are of MTiOXO4 (where M is K, Rb, T1, and/or NH4 and X is P and/or As) having mm2 symmetry. The receiving area of the surface-modified crystal substrates has alternating sections of crystalline material which are aligned and have a ferroelectric domain structure opposite to that of adjacent sections, and IDT for said substrates is in contact with said alternating sections.

Highly stable surface acoustic wave element

Abstract: PURPOSE:To provide a surface acoustic wave element presenting frequency temperature characteristics equivalent to or letter than AT cut utilizing bulk waves by improving the frequency temperature characteristics over a relatively wide temperature range near an ordinary temperature. CONSTITUTION:In this surface acoustic wave element for which an interdigital transducer(IDT) electrode composed of at least one metallic material whose mass is relatively heavy is disposed on the surface of a piezoelectric substrate so as to utilize SH type surface acoustic waves propagated near the surface of the piezoelectric substrate, a quartz substrate cut out so as to let a cutting angle theta to an XY plane be in the range of 27 deg.-37 deg. with a crystal X axis as the center of rotation is used as the piezoelectric substrate. The IDT electrode is constituted so as to let an intra-surface rotation angle psi formed by the phase speed propagation direction of the SH type surface acoustic waves and the crystal X axis be approximately 75 deg.<=¦psi¦<90 deg..

Capacitive charge storing sensor e.g. chemical or biological substances - forms substance-contacting resonator for generating acoustic waves by transmitter and receiver interdigital structures and membrane separated by dielectric gap without mechanical connection.

Abstract: The resonant circuit works with continuous acoustic waves, and the diaphragm acts as a sensor and receiver for the continuous plate waves. The prodn. of the acoustic plate waves in the transmitter transducer results only on the basis of electrostatic attractive force or excitation between the interdigital structures (4) of the transmitter transducer and the diaphragm (1). The output signal of the receiver transducer is decoupled capacitively. The oscillation amplitude of the continuous plate waves is measured by the capacitor formed by the interdigital structure (6) of the receiver transducer and the diaphragm. At the transmitter side, the diaphragm and the interdigital structures (4), and also on the receiver side, the diaphragm (1) and the interdigital structure (6), are separated from each other respectively by spacing in the form of a gap (3) and have no mechanical connection with each other. A dielectric forms the narrow gap, so that a movement of the diaphragm towards the interdigital structures, in the dielectric is possible. USE/ADVANTAGE - E.g. for process and water monitoring, pollution detector, exhaust emission monitoring and gas alarm. Measurement of gaseous and liquid media. Simple and cost effective acoustic-gravimetric sensor. Has very high sensitivity, permits use of thin diaphragm, position of sensor is determined with high resolution.

Harmonic GHz surface-acoustic-wave filters with unidirectional transducers

Abstract: The fabrication of fundamental-mode surface-acoustic-wave (SAW) filters for gigahertz frequencies requires an elaborate photolithographic process. In order to reduce process demands or to increase the possible frequency range, interdigital transducers can be designed to work on spatial harmonics. However, harmonic filters are known to be unattractive because of their high insertion loss. It is shown that harmonic gigahertz filters made with unidirectional transducers can have moderate insertion loss. Two third-harmonic filters at 1.4 GHz and 2.5 GHz, using two-phase unidirectional transducers, are described. A simple model for calculating the input impedance of harmonic surface-transverse-wave (STW) transducers is presented. >

Lamb Wave Propagation Characteristics on Water-Loaded LiNbO3 Thin Plates

Abstract: Propagation characteristics of leaky Lamb waves propagating along a water-solid interface of a rotated Y-cut X-propagation LiNbO3 thin plate are numerically analyzed. Velocity dispersion characteristics, mode conversion efficiency, electromechanical coupling constant of an interdigital transducer and transducer efficiency in the Z-cut plate are described as a function of frequency times substrate thickness. The zeroth-order symmetrical mode has a high coupling constant of over 20% for rotation angles from 0° to 15°. The experimental results obtained from the center frequencies of the leaky Lamb wave devices are in good agreement with results from numerical analysis. The analyzed propagation characteristics and transducer performance are useful in constructing a leaky Lamb wave device with a water-solid interface.

High sensitivity sensor

Abstract: A sensor provided with a thin membrane is capable of storing electric charges and its surface is in contact with the chemical, biological and/or other physical parameters to be measured. The membrane is part of an electromechanical resonance circuit which works with continuous acoustic waves. Opposite to the membrane are arranged transducers provided with interdigital structures for emitting and receiving the continuous acoustic plate waves which act as narrow band filters. The emitting transducer and the receiving transducer are spaced apart by a propagation distance and the signal from the receiving transducer is capacitively detected. An appropriate electronic driving and evaluating circuit or a feed-back is provided between the output signal of the receiving transducer and the emitting transducer. Finally, a direct voltage is applied between the membrane and the emitting transducer, as well as between the membrane and the receiving transducer, upon which is superimposed an alternative voltage at the emitting transducer. The acoustic plate waves at the emitting transducer are solely generated by the electrostatic attraction or excitation between the interdigital structures of the emitting transducer and the membrane. The output signal of the receiving transducer is uncoupled in a capacitive manner in such a way that the oscillation amplitude of the acoustic continuous plate wave is measured in the receiving transducer by the capacitor formed by the interdigital structures of the receiving transducer and the membrane. On the emitting side, the membrane is spatially separated from the interdigital structures of the emitting transducer by a gap, and on the receiving side, it is spatially separated from the interdigital structures of the receiving transducer by another gap. There is no fixed mechanical connection between the membrane and the interdigital structures of the emitting and receiving transducers, so that the narrow gap forms a dielectric in which the membrane can move in the direction of the interdigital structures.

Reflective piezoelectric delay line for surface acoustic waves - features single acoustic track leading in one or both directions from interdigital transducer to retroreflecting structures

Abstract: An input/output interdigital transducer (2) is provided on a piezoelectric substrate (1) to radiate a surface acoustic wave into a single track (7) along which a number of conventional reflectors (3-6) is arranged A unidirectional formation of reflective interdigital transducers or multi-strip couplers gives the advantage of either lower attenuation or multiple reflections from weaker structures in the losses of bidirectionality The reflectors may be acousto-mechanical or regenerative structures, or special structures as in DE 4115700 ADVANTAGE - Compact and easily mfd device characterised by low deg of scattering and diffraction loss

Imaging of electrostatic electric fields of SAW structures using electro-optic effects

Abstract: The design and analysis of SAW interdigital transducers (IDTs) requires the accurate translation of transducer weighting information to the IDT structural geometry. The electrostatic electric field is the dominant excitation mechanism of the IDT for the generation of surface waves. Measurement of the actual charge distribution and wave generation sites enables the verification of the implemented impulse response weighting. To date, the measurement of the wave generation and propagation requires elaborate laser probing stations. This paper investigates a method to obtain images of the field distribution between the electrodes of an interdigital transducer in a SAW device. This method is based on the birefringence effects found in piezoelectric materials. Using an optical microscope with appropriate linear polarization of a non-coherent visible light source, the electric field induced by the applied DC terminal voltage may be viewed. The technique is based on the rotation of polarization of the transmitted light and resulting modulation of the light intensity, which occurs in the presence of an applied electric field. The visible modulated light intensity is a mapping of the tangential electric field between the IDT electrodes. The results of the measurement can be used to identify the SAW structure's radiation locations and relative strengths for accurate modeling of the device response. Optical measurement of the electric field strength for a SAW split electrode transducer on YZ-LiNbO3 is presented and compared to theoretical predictions

Ultrasonic transducer for liq. dispersion medium - has epoxy] hardened adaptation layer to prevent interfacial reflections

Abstract: Ultrasonic transducer has piezoelectric transducer element, and adaptation layer adjacent to the dispersion medium. The latter has acoustic impedance between that of the transducer element and that of the medium, and comprises solid glass or silica spheres which are bonded by means of an organic resin (e.g. an epoxy resin) to form composite material having acoustic impedance matched to that of the liq. medium, so that reflections at this adaptation layer are almost completely prevented. Pref. ultrasonic frequencies of 1-2 MHz, the average dia. of the glass spheres is less than 0.2 mm. Metal ring is attached round the cylindrical edge of the circular piezoelectric transducer element, to damp the radial vibrations of the transducer element. The transducer comprises piezoelectric transducer element (2) centrally arranged in housing (1). The front face of the transducer is formed from the adaptation layer (3) which is situated on the ring section (4). The channel (5) is used for adhesive or solder connection. The rear face of the transducer element (2) is covered with castable, sound-absorbing material (6). The elctrical supply cables are at (7). ADVANTAGE - The invention claims to tailer the design of the device strictly according to the relevant laws of physics for this system.

On the application of the Wiener-Hopf technique to electrostatic field problems in interdigital transducers

Abstract: The Wiener-Hopf technique is used to compute the electrostatic field distribution in an interdigital transducer at the plane interface between two dielectric media sandwiched between two grounded metallic plates, with two grounded semi-infinite neighboring plates at the interface on each side of the transducer. To this end, the associated Green's function, which already satisfies the boundary conditions at all the grounded plates, is computed. The Green's function is used to derive the elements of the charge-potential-interrelation matrix for various basis and testing functions for a method-of-moments application. Examples demonstrate that the method has considerable advantages with respect to accuracy and computer-memory requirements. >