Showing papers on "Interdigital transducer published in 2005"

Growth of AlN piezoelectric film on diamond for high-frequency surface acoustic wave devices

Abstract: Diamond films are very desirable for application to SAW devices because of their high acoustic wave velocity, which allows the extending of the frequency limit of operation at a given interdigital transducer line-width resolution. Use of high-quality AlN as the piezoelectric layer in conjunction with diamond is also desirable because of its high SAW velocity - the highest among all piezoelectric materials - together with its excellent electrical, mechanical, and chemical properties. The problems arising in the growth of AlN films on diamond have prevented, until now, the use of this combination of materials. In this paper we present recent results on the growth of highly oriented, low-stressed AlN films on diamond. SAW propagation on AlN/diamond has been theoretically investigated together with electromechanical coupling for both the Rayleigh and the Sezawa modes. The theoretical calculations show that high SAW velocities are achievable with good coupling efficiencies. Under proper conditions very large piezoelectric couplings are predicted k/sup 2/ = 2.2 and 4% for the Rayleigh and the Sezawa wave, respectively comparable to those observed in strongly piezoelectric single crystals such as LiNbO/sub 3/, but with SAW velocities approximately two-fold higher. Experiments performed on AIN/diamond/Si SAW test devices have shown good agreement between experimental results and theoretical predictions and demonstrate the feasibility of SAW devices based on this technology.

Platinum and palladium high-temperature transducers on langasite

Abstract: There is a pressing need for the fabrication of surface acoustic wave (SAW) devices capable of operating in harsh environments, at elevated temperature and pressure, or under high power conditions. These SAW devices operate as frequency-control elements, signal-processing filters, and pressure, temperature , and gas sensors. Applications include gas and oil wells, high-power duplexers in communication systems, and automobile and aerospace combustion engines. Under these high-temperature and power-operating conditions, which can reach several hundred degrees centigrade, the typically fabricated aluminum (Al) thin film interdigital transducer (IDT) fails due to electro and stress migration. This work reports on high temperature SAW transducers that have been designed, fabricated, and tested on langasite (LGS) piezoelectric substrates. Platinum (Pt) and palladium (Pd) (melting points at 1769/spl deg/C and 1554.9/spl deg/C, respectively) have been used as thin metallic films for the SAW IDTs fabricated. Zirconium (Zr) was originally used as an adhesion layer on the fabricated SAW transducers to avoid migration into the Pt or Pd metallic films. The piezoelectric LGS crystal, used as the substrate upon which the SAW devices were fabricated, does not exhibit any phase transition up to its melting point at 1470/spl deg/C. A radio frequency (RF) test and characterization system capable of withstanding 1000/spl deg/C has been designed and constructed. The LGS SAW devices with Pt and Pd electrodes and the test system have been exposed to temperatures in the range of 250/spl deg/C to 750/spl deg/C over periods of up to 6 weeks, with the Saw devices showing a reduced degradation better than 7 dB in the magnitude of transmission coefficient, |S/sub 21/|, with respect to room temperature. These results qualify the Pt and Pd LGS SAW IDTs fabricated for the above listed modern applications in harsh environments.

Analysis and design of focused interdigital transducers

Abstract: Focused interdigital transducers (FIDTs) can generate surface acoustic wave (SAW) with high intensity and high beamwidth compression ratio. Owing to these features, they are very suitable to be used as the sources of microacoustic channels or waveguides in the near future. The focusing properties of FIDTs are dominated solely by their geometric shapes. Therefore, to obtain optimal performance, it is essential to analyze the FIDTs with a variety of geometric shapes. However, among the existing studies concerning the diffraction of FIDTs, a detailed analysis and design of FIDTs is still in paucity. In this paper, we adopted the exact angular spectrum of plane wave theory (ASoW) to calculate the amplitude fields of FIDTs on Y-Z lithium niobate (LiNbO/sub 3/) with the shape as a concentric circular arc and the concentric wave surface. Based on the calculation results, we discussed the variations of the amplitude fields induced by changing number of pairs, degree of arc, and geometric focal length. In addition, the focusing properties of FIDTs on the (100)-oriented GaAs substrate were also analyzed and discussed. We also summarized the guiderules for designing a FIDT via four important factors. It is worth noting that the results of this study provide an important basis for designing various FIDTs to fit the desired applications.

Surface acoustic wave device

Abstract: PROBLEM TO BE SOLVED: To provide a surface acoustic wave device which has high frequency precision as well as frequency stability, simple manufacturing process, and low manufacturing cost. SOLUTION: A surface acoustic wave element in which an IDT (Interdigital Transducer) electrode formed on a main face of piezoelectric substrate of rectangular form is covered with a protecting film, is mounted on a substrate as it is held only at an end side or the center part. An arbitration film of identical composition to the protecting film is attached on the other main face of the piezoelectric substrate. COPYRIGHT: (C)2005,JPO&NCIPI

Surface Acoustic Wave Filters

Abstract: Currently, surface acoustic wave (SAW) filters are widely used in RF stages as well as IF stages of modern telecommunication systems With successful research and development of SAW devices since the early 1960s, the growth of mobile phone markets has accelerated, with surprising advances in SAW device technologies since the early 1990s This article discusses how the filtering function of SAW devices is realized using various SAW propagation phenomena, and reviews the performance of current commercial SAW filters First, SAW transversal filters are discussed Starting from a brief discussion of their fundamentals, we describe achievable performance, impact of the substrate selection and the most recent advances of this type of filter Next, filters based on SAW resonators are discussed After giving basic ideas of SAW resonators, it is shown how SAW resonator filters are composed and designed using SAW resonators Keywords: surface acoustic wave; SAW; resonator; transversal filter; dispersive delay line; piezo-electricity; unidirectional transducer; interdigital transducer; SPUDT; DMS; dual-track-filter; Z-path filter; fan-shaped filter; resonant SPUDT; double-mode resonator filter; ladder-type filter; duplexer

Active micromixer using surface acoustic wave streaming

Abstract: An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

A flexible piezoelectric transducer design for efficient generation and reception of ultrasonic Lamb waves

Abstract: This paper describes the development of a flexible piezoelectric transducer for the generation and detection of ultrasonic symmetrical Lamb waves in plate-like structures. This piezoplatelet transducer structure comprises an array of miniature piezoceramic plates embedded within a soft setting polymer filler material, combining the efficiency of the active piezoceramic phase with a degree of flexibility, which is a function of the platelet/polymer dimensions. For many condition-monitoring applications, the generation of ultrasonic Lamb waves is often appropriate, and this was achieved by incorporating interdigital design techniques via the transducer electrode pattern. The performance of the piezoplatelet transducer structure was evaluated using a combination of linear systems and finite-element modeling, substantiated by experimental results. Importantly, the transducer is shown to operate as an ensemble of platelets, each operating in the thickness mode and well decoupled from neighboring piezoelectric elements. Using this transducer configuration, an unimodal s/sub 1/ Lamb wave, at 1.45 MHz, has been generated and detected in a 3-mm thick steel plate. Furthermore, a propagation distance of almost 1 m was recorded for s/sub 0/ Lamb wave generation/detection in a fiber-reinforced composite plate.

Passive and wireless in-vivo acoustic wave flow sensor

Abstract: A wireless surface wave flow sensor can be utilized for monitoring the flow of fluid Such a surface wave flow sensor can be configured to include one or more interdigital transducers and a self-heating heater formed upon a piezoelectric substrate The interdigital transducer(s) can be selected to convert electrical signals to surface waves thereof An antenna can also be connected to the surface wave device, wherein the antenna can receive one or more signals, which excites the acoustic device to produce a frequency output associated with the flow of the fluid for analysis thereof

Wireless passive SAW sensors using single-electrode-type IDT structures as programmable reflectors

Abstract: Sensor information can be read out wirelessly by an antenna if the surface acoustic wave (SAW) delay line is connected to an external classical sensor. This is a passive device also called impedance-loaded SAW sensor. In the last decade, many researchers have made great efforts researching such devices, in which the double-electrode-type interdigital transducer (IDT) has been used as programmable reflector because its short-circuit reflection coefficient is very small. In this paper, the single-electrode-type IDT structure is proposed to be used as programmable reflector. The metallic periodic structure deposited on 128°YX LiNbO 3 shows an extraordinary characteristic: for a certain ratio of the film thickness to the periodicity, the reflection of the short-circuited single-electrode-type IDT almost disappears. This characteristic enables great amplitude modulation when the impedance-loaded SAW sensor employs the single-electrode-type IDT as programmable reflector. The fundamental operating frequency of SAW devices using the single-electrode-type IDT structure is twice that of SAW devices using the double-electrode-type IDT structure with the same critical dimension. This means higher operating frequencies for such devices can be reached with the achievable linewidth in current manufacturing technologies.

X-ray topography analysis of acoustic wave fields in the SAW-resonator structures

Abstract: The formation of fields of standing surface acoustic waves (SAW) in LiNbO/sub 3/ and La/sub 3/Ga/sub 5/SiO/sub 14/ (LGS) crystals was studied by high-resolution topography method on a laboratory X-ray source. The fields of standing SAW were formed using SAW-resonator structures consisting of interdigital transducer (IDT) and reflecting gratings. The SAW amplitudes and power flow angles were measured by X-ray topography, diffraction in acoustic beam was visualized, and the SAW interaction with the crystal structure defects was studied.

Side-gate effects on transfer characteristics in GaN-based transversal filters

Abstract: We examine the transfer characteristics of transversal filters with side gates fabricated on unintentionally doped GaN layers grown on (0001) sapphire substrates. By positively biasing the side gates, the transfer characteristics of the filters are efficiently improved, which means that GaN-based transversal filters with side gates are potentially applicable for filtering and modulating rf signals. We further examine the capacitance in an interdigital transducer, which decreases when the side-gate bias voltage increases. This indicates that the variation in the transfer characteristics is likely to be attributable to a change in the depletion-layer thickness in the GaN layers.

Piezoelectric resonator and electronic component provided therewith

Abstract: A piezoelectric resonator according to an embodiment of the present invention has a first transducer connected to a first signal terminal, and a second transducer connected to a second signal terminal. The first transducer and the second transducer are stacked in a predetermined direction. At least one of the first transducer and the second transducer has a first piezoelectric film sandwiched between a pair of electrode films on both sides, and a second piezoelectric film comprised of a film type different from that of the first piezoelectric film and sandwiched between a pair of electrode films on both sides.

An ultrasonic nondestructive technique for evaluating layer thickness in human teeth

Abstract: An ultrasonic nondestructive evaluation technique of the layer thickness in human teeth using a leaky Lamb wave device with two arch-shaped interdigital transducers (IDTs) is proposed. Each of the two IDTs on a piezoelectric ceramic plate operates as an input or an output transducer at a plate/water interface, in the configuration of an acoustic delay line of reflected ultrasound beams from the tooth section at the spot under investigation. The use of a higher-order mode, second symmetric (S2) mode, leaky Lamb wave with a phase velocity higher than the longitudinal wave velocity in the human tooth is essential to enable the oblique incidence of the focused ultrasound beam. The echoes from dentin–pulp and enamel–dentin junctions are similar in the oscilloscope traces. The layer thickness of dentin or enamel for a number of teeth, estimated from the measured time interval between two reflected echoes, from the tooth surface and from the interface in the tooth, is in good agreement with the optically measured data.

Surface acoustic wave investigations of the metal-to-insulator transition of V2O3 thin films on lithium niobate

Abstract: Thin V2O3 films were deposited on a piezoelectric substrate by electron-beam evaporation. Surface acoustic waves were generated by interdigital transducers. The attenuation and sound velocity were investigated from 260 to 10 K, providing an insight into the temperature-dependent electrical, dielectrical, and elastic properties of V2O3 at the metal-to-insulator transition.

Surface Acoustic Wave Resonator and Surface Acoustic Wave Filter Using the Same

Abstract: A Q-factor of a resonator at a high frequency is improved. An insertion loss of a filter using such a resonator and steepness of the filter are improved. A plurality of surface acoustic wave resonators including an interdigital transducer and reflecting electrodes provided on both sides thereof are connected in parallel on a piezoelectric substrate. Resonance frequencies of the surface acoustic wave resonators are rendered equal among all the resonators connected in parallel. In this way, the Q-factor of the resonance can be improved. A surface acoustic wave filter using such surface acoustic wave resonators is formed in order to improve the insertion loss and the steepness.

Wireless and passive acoustic wave rotation rate sensor

Abstract: A rotation rate sensing apparatus is configured from an acoustic wave device comprising a plurality of interdigital transducers for the SAW configuration or electrodes for vibration beams configuration. Such sensors are configured upon an elastic substrate. In the SAW configuration, the plurality of interdigital transducers includes a first interdigital transducer, a second interdigital transducer and a third interdigital transducer. A generator(s) can be formed from the first and third interdigital transducers, wherein the generator generates a standing wave subject to a Coriolis force by adding two progressive waves at each of the first and third interdigital transducers. In the vibration beams configuration, a drive beam(s) and pickup beam(s) can be implemented such that the vibration beams are excited through an RF signal and a Coriolis force excites the pickup beam(s) in order to obtain angular/rotation rate data.

Surface acoustic wave device and electronic apparatus

Abstract: A surface acoustic wave device (10) including at least an interdigital transducer electrode (12;21,22) that excites a Rayleigh surface acoustic wave on a surface of a crystal substrate (11) and giving excitation in an upper limit mode of a stopband of the surface acoustic wave, wherein Euler angle representation (Φ,θ,ψ) showing a cut angle and surface acoustic wave propagation direction of the crystal substrate is set as (0°,0° ≤ θ ≤ 180°,0° < |ψ| < 90°), preferably (0°,95° ≤ θ ≤ 155°,33° < |ψ| < 46°) or (0°,123°,41°).

Layered surface acoustic wave sensor

Abstract: A surface acoustic wave sensor which incorporates: a) a first layered SAW device consisting of a piezoelectric crystal such as lithium niobate or lithium tantalate with interdigital electrodes on its surface, and second piezoelectric layer such as zinc oxide over said interdigital electrodes b) a second layered SAW device consisting of a piezoelectric crystal with interdigital electrodes on its surface, a second piezoelectric layer over said interdigital electrodes and an analyte sensitive surface such as gold on said second piezoelectric layer c) both saw devices are fabricated on the same substrate d) reflectors are located adjacent the interdigital electrodes in each saw device to reduce the bandwidth of the device e) the resonator circuits of each saw sensor incorporate amplifiers which are dependent.

Evaluation of elastic properties of submicrometer thin films using slanted finger interdigital transducers

Abstract: Accurate evaluation of film properties with thickness in the submicrometer range is very important throughout microelectronic industry as well as nano/microelectromechanical system industry. In this study, we developed a nondestructive evaluation technique, which is not only suitable for dielectric films but also valid for metallic films, to measure the elastic properties of submicrometer thin films. Firstly, we established the forward solution of the inverse evaluation and analyzed the dispersion of surface acoustic wave (SAW) in a SiO2∕YZ–LiNbO3 coated solid based on the effective permittivity approach. To measure the dispersion of SAW in the coated solid, a slanted finger interdigital transducer (SFIT) was employed to generate wide band SAW signals. The SFIT was designed by using the coupling of modes method to obtain the optimal frequency response. SiO2 films with submicrometer thickness were deposited on the piezoelectric YZ–LiNbO3 substrate via the plasma-enhanced chemical-vapor deposition process. ...

Surface acoustic wave resonator and surface acoustic wave filter using it

Abstract: A Q value of a resonator at a high frequency is improved, and by using such resonator, a filter insertion loss is reduced and filter steepness is improved. The surface acoustic wave resonator is provided with an interdigital transducer and reflecting electrodes on the both sides of the interdigital transducer. On a piezoelectric board, a plurality of the surface acoustic wave resonators are connected in parallel, and all the resonant frequencies of the surface acoustic wave resonators connected in parallel are permitted to be the same. Thus, the resonance Q value is improved, and by configuring the surface acoustic wave filter by using the surface acoustic wave resonator, the insertion loss is reduced and the steepness is improved.

Passive and wireless acoustic wave accelerometer

Abstract: An acoustic wave acceleration sensor comprises an acoustic wave device including a plate that functions as a propagation medium and at least one interdigital transducer configured upon the plate. One or more antennas can be integrated with the acoustic wave device, wherein the antenna(s) communicates with interdigital transducers. Such antennas can receive wireless interrogation signals and transmit signals indicative of acceleration data.

Multiple-mode acoustic wave sensor

Abstract: A multiple-mode acoustic wave sensor apparatus includes an acoustic wave device comprising a piezoelectric substrate and at least one electrode on the substrate. When such sensor is used in a wireless configuration, a plurality of antennas can be configured on the substrate in association with the acoustic wave device, wherein each antenna among the plurality of antennas is responsive to varying interrogation signals transmitted wirelessly to the plurality of antennas in order to excite multiple frequency modes via at least one interdigital transducer on the substrate and thereby passively detect multiple and varying parameters of a sensed material utilizing the acoustic wave device.

Analytical Solution for Shear Horizontal Wave Propagation in Piezoelectric Coupled Media by Interdigital Transducer

Abstract: An analytical solution for the shear horizontal wave propagation excited by interdigital transducer in a piezoelectric coupled semi-infinite medium is developed. This solution is an extension of earlier work on wave propagation in a piezoelectric coupled plate with finitely long interdigital transducer by fully taking account of piezoelectric effects in analysis. In the current analysis, the mathematical model for a semi-infinite metal substrate bonded by a layer of interdigital transducer with infinite length is first derived. The theoretical solutions are obtained in terms of elliptic integration of the first kind and of the standard integral representation for Legendre polynomial. The essential hypothesis for the derivation of the analysis is investigated. Based on the solution for infinitely long interdigital transducer, an analytical solution for the wave propagation in this semi-infinite piezoelectric medium excited by a finitely long interdigital transducer is obtained through Fourier transform. This theoretical research can be applied to health monitoring of structures by interdigital transducer. It could also be used as a framework for the design of interdigital transducer in wave excitation of smart structures.

Numerical analysis of Lamb wave generation in piezoelectric composite IDT

Abstract: An equivalent, single-layer model for Lamb wave generation by interdigital transducer (IDT) on composite host structures is developed. The additional complexities generally encountered while launching the surface acoustic wave (SAW) on composite structure, such as the coupling between the Lamb wave modes, the complicated nature of the electromechanical actuation etc. are considered. The model of infinite IDT is extended to deal with the finite IDT with edge discontinuities. The effect of electromechanical actuation on the wavelength shifts with respect to the passive case is investigated. The problem of electrically driven instability within the IDT is analyzed. Numerical results are reported by considering a model of the IDT integrated with the host structure, which shows that there are significant deviations from the conventional design estimates while launching a targeted mode. The proposed approach may enable one to obtain new designs in material systems arid geometry that avoid mode-mixing, or to introduce it by choice.

Acoustic wave flow sensor

Abstract: An acoustic wave flow sensor is disclosed, which includes a sensor substrate and an acoustic wave diaphragm etched upon the sensor substrate, wherein mechanical stress or strain is concentrated in the acoustic wave diaphragm. One or more interdigital transducers can be configured upon the acoustic wave diaphragm, wherein the sensor substrate, the acoustic wave diaphragm and the interdigital transducer(s) form an acoustic wave flow sensor, such that when the interdigital transducer and the acoustic wave diaphragm are exposed to a fluid in flow, the fluid in flow causes the acoustic wave diaphragm to experience a change in the mechanical stress or strain resulting in a detectable frequency and/or phase change in order to provide an indication of fluid flow.

Surface acoustic wave body

Abstract: PROBLEM TO BE SOLVED: To reduce the thickness of a surface acoustic wave body mainly used for mobile communication equipment. SOLUTION: This surface acoustic wave body is provided with a silicon substrate 12, piezoelectric thin film 13 provided on the top surface of this silicon substrate 12, surface acoustic wave element configured by an interdigital transducer 14 provided on the top surface of this thin film 13, pad electrode 15 electrically connected to this surface acoustic wave element and provided on a portion other than the surface acoustic wave element on the top surface of the thin film 13, through hole 17 penetrating the thin film 13 and the silicon substrate 12 on a lower part of this pad electrode 15, conductive material filled in this through hole 17, and external terminal 24 provided on the bottom surface side of the silicon substrate 12. The pad electrode 15 and the external terminal 24 are each a surface acoustic wave element electrically connected via the conductive material in the through hole 17. Thus, the surface acoustic wave body is reduced in thickness. COPYRIGHT: (C)2006,JPO&NCIPI

Passive wireless surface acoustic wave chemical sensor

Abstract: A passive wireless acoustic wave chemical sensor can be utilized for monitoring the concentration of an analyte in a substance such as blood. Such an acoustic wave chemical sensor can be configured to include one or more interdigital transducers and a selective coating formed upon a piezoelectric substrate. The coating and the interdigital transducer(s) can be used to convert electrical signal to surface waves thereof. An antenna can be connected to the acoustic wave device, wherein the antenna receives one or more input signals, which excite the acoustic device and to produce an output signal that is related to the concentration of the analyte of interest.

Improved pure SH SAW transduction efficiency on LGS using finite thickness gratings

Abstract: Pure shear horizontal surface acoustic wave (SH SAW) orientations exist on trigonal class 32 crystals along (0°, θ, 90°). In particular, this mode has been recently considered on single crystal langasite (LGS) for liquid and biological sensor applications due to reduced propagation loss in the presence of liquid-loaded surface. A limitation of the pure SH SAW orientations for device applications has been the significant excitation of the shear horizontal bulk acoustic wave (SH BAW) by the interdigital transducer (IDT), which compromises the SH SAW transduction efficiency and thus increases SH SAW device loss. Previous work by the authors verified that an infinitesimally thin metallic guiding layer used in the propagation path around the IDT typically increases the SH SAW transduction efficiency ηSHSAW , defined as the ratio of SH SAW power to total IDT input power, from less than 1% (no layer) to 60% (infinitesimally thin metallic layer) on LGS, Euler angles (0°, 22°, 90°) for a 240 split finger electrode IDT. In this work, finite thickness periodic grating guiding structures are explored along LGS (0°, 22°, 90°) to further improve the IDT ηSHSAW. The structure studied consists of a finite number of IDT electrodes bordered by gratings on both sides. The model implemented uses orthogonal Chebyshev polynomial basis functions in conjunction with the finite element method and harmonic admittance (HA) technique to study the SH SAW mode excitation efficiency in the referred structure. The IDT ηSHSAW is examined as a function of: electrode material and normalized thickness (h/λ) where h is electrode thickness and λ is the wavelength; metallization ratio (a/p) where a and p are electrode width and center-to-center spacing, respectively; and number of split IDT finger electrodes. The analysis performed shows a significant difference in ηSHSAW if high density electrode gratings, such as gold (Au) or platinum (Pt) are used instead of low-density gratings, such as aluminum (Al). For instance, using 282 split finger electrode IDT and surrounding gratings composed of Au or Pt electrodes, with h/λ = 1%, results in ηSHSAW = 99%. If Al is used, a reduced ηSHSAW = 54% is achieved for the same h/λ = 1%. Moreover, to achieve ηSHSAW = 99% with Al electrodes, the required value of h/λ is about 8.5%, a nearly ten-fold increase in metallization thickness over Au or Pt electrodes. The effects of metallization ratio a/p on ηSHSAW have also been studied and indicate that higher metallization ratios lead to higher ηSHSAW. Numerical and experimental IDT admittance is compared, validating the analysis performed. The work reported shows that finite thickness gratings can significantly improve the SH SAW IDT performance, reducing the amount of SHBAW excited by the IDT, and thus leading to high efficiency LGS SH SAW devices for biosensor applications.

Elastic wave apparatus

Abstract: A surface acoustic wave apparatus is configured to avoid destruction from static electricity. The surface acoustic wave apparatus includes a piezoelectric substrate; a surface acoustic wave element having at least one interdigital electrode made up of a conductive film on the piezoelectric substrate; and a thin film electrically connected between terminals connecting to electrode fingers of the interdigital electrode, the thin film showing varistor characteristics formed on the piezoelectric substrate.