Showing papers on "Interdigital transducer published in 1995"

Sensors based on piezoelectric resonators

Abstract: A review of sensors based on piezoelectric crystal resonators is presented. The survey focuses on the fundamental resonator modes rather than on the variety of surrounding support configurations in special sensor applications. First, the general properties of vibrating crystal sensors and their inherent superiority are described. The sensor concepts utilizing either homogeneous resonators with temperature and pressure (stress) as primary measurants or composite resonators with areal mass density and viscoelastic properties of the 'foreign' layer as primary measurands are discriminated. A comparison between bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators with respect to their primary sensitivity functions and principal capabilities for sensor applications is given and the importance of recent investigations on Lamb wave and horizontal polarized shear wave (HPLW) interdigital transducer (IDT) resonators is acknowledged. The importance of mode purity for high dynamic range sensors based on resonators and some aspects of the demand on specialized electronics are emphasized. The present state of established sensors based on primary sensitivities, e.g., quartz-crystal thermometers, pressure transducers, thin-film thickness and deposition-rate monitors, viscoelastic layer analysers (crystal/liquid composite resonators) is reviewed. A selection of the most promising recently investigated vibrating crystal sensors utilizing indirect sensitivities is described, including the wide field of analyte-selective coatings and resonator-based immunosensors or immunoassays. Finally, the potential of alternative piezoelectric materials for future sensor developments is briefly discussed.

Ultrasonic transducer array and method of manufacturing the same

Abstract: In a method of manufacturing an ultrasonic transducer array a plurality of discrete transducer elements are formed on an initially flat flexible substrate together with electrically conductive tracks, through which the transducer elements will be energised in use, the flexible substrate with the discrete transducer elements and conductive tracks mounted thereon then being formed into a cylinder and mounted on the end of a catheter tube, the substrate being radially outwardly of the transducer elements so that it is in a position to act also as an acoustic matching layer between the material of the transducer elements and the human tissues or blood when in use.

Combustion gas sensitivity of zeolite layers on thin-film capacitors

Abstract: Y-zeolites doped with platinum by an ion-exchange process have been used as gas-sensitive layer material on thin-film interdigital capacitors (IDCs). The zeolite-IDC sensor sensitivity has been determined for C 4 H 10 , CO and H 2 in wet air by exciting the sensor with an alternating voltage and determining the impedance response.

AlN/silicon Lamb-wave microsensors for pressure and gravimetric measurements

Abstract: We have studied a pressure and a gravimetric sensor using an AlN film over a silicon membrane. The membrane is micromachine using both anisotropic and isotropic chemical etching. The AlN thin film is deposited by the sputtering method. Elastic waves are generated and detected through interdigital transducers (IDTs) calculated at the frequency of 90 MHz for the S 0 Lamb-wave mode. The behaviour of such a sensor is presented. We have analysed and experimentally tested the pressure and have calculated the gravimetric sensitivity. By using the opposite temperature behaviours of silicon and AlN, a satisfactory temperature compensation is achieved. Results obtained from such experiments show sensitivities that agree with theoretical sensitivities provided by a theoretical model which includes the effect of the mass loading of the deposited thin-layer material.

Methods of manufacture for electronic components having high-frequency elements

Abstract: Integrated circuits utilizing piezoelectric elements can be advantageously constructed by bonding elements together via direct bonds. Such integrated circuits include an electro-acoustic hybrid integrated circuit such as a voltage controlled oscillator wherein a semiconductor substrate having an active element is bonded through direct bonding to a surface acoustic wave resonator or a quartz oscillator as an electro-acoustic element. A quartz device can also be provided which includes a quartz plate, excitation electrodes on opposite surfaces, and a holding member made of a material having a thermal expansion coefficient substantially equal to that of the quartz plate. The holding member is connected to the quartz plate by direct bonding without using any adhesives. Because the thermal expansion coefficients of the quartz plate and the holding member are equal, no thermal stress occurs in the bonding area. As a result, virtually no stress is applied to the quartz plate and the frequency-temperature characteristic can be improved. A piezoelectric filter according to the invention includes an oscillatory piezoelectric plate made of quartz, lithium tantalate, lithium niobate or lithium borate and having an oscillatory portion; a glass plate to which the piezoelectric plate is directly bonded; and first and second oscillatory electrode members which are provided on opposite faces of the oscillatory portion, respectively, such that at least one of the oscillatory electrode members is divided into a plurality of counter electrodes.

Surface acoustic wave device.

Abstract: A SAW device formed by providing at least one interdigital transducer (23) on a piezoelectric substrate (22) which is prepared by forming a (1120) ZnO piezoelectric thin film (22b) on a (0112) plane alpha -Al2O3 substrate (22a), and forming reflectors (24, 25) on both sides of the interdigital transducer (23) along a surface wave propagation direction. Each of the reflectors (24, 25) is so structured that a ratio H/ lambda of its thickness H to a wavelength lambda of a surface wave is in a range of 0.015 to 0.041.

Composite piezoelectric transducer arrays with improved acoustical and electrical impedance

Abstract: Transducer elements having a 2-2 or 1-3 composite structure and driven in a k 31 transverse mode for small-feature size transducer arrays, which provide improved electrical impedance matching to an ultrasonic imaging system and improved acoustic matching to the human body. The transducer element includes a plurality of thin piezoceramic wafers which are electroded on opposing major surfaces. The spaced wafers are separated by a passive polymer layer in a composite structure. Methods of producing the transducer elements are also described.

Balanced type surface acoustic wave device

Abstract: The present invention provides surface acoustic wave devices which do not require a balanced-to-unbalanced transformer circuit regardless of the type of the peripheral circuits of the balanced type surface acoustic wave filter, i.e. a balanced type device or an unbalanced type. A transmitting interdigital transducer and a receiving interdigital transducer are formed on a substrate comprising 41° Y cut-X propagation lithium niobate. A balanced type surface acoustic wave filter is formed on a substrate comprising 36° Y cut-X propagation lithium tantalate. The balanced type surface acoustic wave filter comprises two series-arm surface acoustic wave resonators and two crossed-arm surface acoustic wave resonators connected in a lattice. The substrate on which the transmitting interdigital transducer and the receiving interdigital transducer are formed and the substrate on which the balanced type surface acoustic wave filter is formed are located in a ceramic package. One of the input terminals of the transmitting interdigital transducer is grounded. The output terminals of the receiving interdigital transducer are connected to the input terminals of the balanced type surface acoustic wave filter.

SAW impedance elements

Abstract: In the past few years a new class of SAW devices has been under development based on the use of one port SAW resonators as lumped elements with their impedance strongly changing in a frequency range of effective SAW excitation These 'SAW impedance elements' can be connected in ladder type, balanced bridge type, or others types of networks to provide desired filter characteristics In this paper the admittance characteristics of a single element are analyzed using coupling of mode (COM) model simulations It is found that resonant type characteristics of a long transducer can be described by very simple formulas The frequency gap between resonance and anti-resonance, important for filter design, is determined practically by the /spl Delta/V/V parameter of the piezoelectric substrate used, while the minimum magnitude of the impedance at the resonant frequency is determined by the SAW attenuation The internal reflections only shift the resonance to the left edge of the stopband not changing other characteristics A case of a synchronous resonator comprising a relatively short transducer and two reflectors placed on both sides of it is also analyzed This type of impedance element has smaller frequency shift between resonance and anti-resonance points >

Acoustic wave devices employing surface skimming bulk waves

Abstract: An acoustic wave device employing surfaces skimming bulk waves comprises a piezo electric substrate having a flat surface which carries an input transducer and an output transducer for respectively lanuching and receiving acoustic waves into and from the bulk of the substrate. The substrate may be of quartz, lithium tantalate, or lithium niobate and has the flat surface orientated so that a surface skimming bulk wave is launched without generation of surface acoustic waves.

Surface acoustic wave filter

Abstract: PURPOSE:To prevent an electrode from being fused even in the case of using a surface acoustic wave (SAW) filter having narrow interdigital transducer electrode (IDT) line width by forming input side and output side IDTs on a base and arranging a shielding electrode between the input side and output side IDTs separately from a pair of input IDTs respectively by specific distances or more. CONSTITUTION:Input and output IDTs 3, 4, 1, 2 having comb line electrodes with 1.2mum opposed distances are formed on the surface of a lithium niobate piezoelectric monocrystal base 6 for 128 deg. Y axis cutting and X axis propagation by using split electrodes with 1.27Xm line width. The IDT 3 out of the input side IDTs 3, 4 is potentially independent and the IDT 4 is connected to the stem of a package through a bonding wire and set up to ground potential. Output side IDTs 1, 2 are mutually independent and potentially independent of the stem. The shielding electrode 5 is arranged between the input side IDTs 3, 4 and the output side IDTs 1, 2. A gap between the electrode 5 and the IDT 3 is set up to 70Xm. The and a gap between the electrode 5 and the IDT 2 is set up to 70Xm. The center frequency of the SAW filter is 402.78MHz and its 3dB band width is 27MHz.

Qualitative and quantitative gas analysis with non-linear interdigital sensor arrays and artificial neural networks

Abstract: Interdigital sensors are well suited to the quantitative and qualitative analysis of gases and vapours. The surfaces of the sensors are coated with substances which are also used in gas chromatography. The signals for the gas analysis are the relative changes of the electrical conductance and capacity. The disadvantages of these sensor elements are their non-selectivity and their non-linear transfer characteristics. Artificial neural networks are used for pattern recognition of multicomponent sensor systems. The paper describes a modification of the conventional signal evaluation technique using neural networks to evaluate the concentrations of a gas mixture.

SPICE simulation of surface acoustic wave interdigital transducers

Abstract: Surface Acoustic Wave (SAW) devices, are not normally amenable to simulation through circuit simulators. In this letter, an electrical macromodel of Mason's Equivalent Circuit for an interdigital transducer (IDT) is proposed which is compatible to a widely used general purpose circuit simulator SPICE endowed with the capability to handle negative capacitances and inductances. Illustrations have been given to demonstrate the simplicity of ascertaining the frequency and time domain characteristics of IDT and amenability to simulate the IDT along with other external circuit elements. >

Withdrawal weighted fan-shaped SAW transducers

Abstract: Withdrawal weighted (WW) fan-shaped interdigital transducers (FIDT) are used to design surface acoustic wave (SAW) filters with a good shape factor, a flat passband, and an out-of-band rejection of 50 dB and more. Utilization of "stepped" actions as a weighting action for FIDT's ensures a simple filter structure synthesis procedure that does not take a long time on a personal computer. Three modifications of SAW filters with 2% bandwidth, in-band ripple of 0.1 dB, and out-of-band rejection of 50-55 dB have been fabricated on ST-quartz. >

Effect of surface acoustic waves on activity in heterogeneous catalysis

Abstract: A synopsis of the recent developments in acoustically influencing and controlling gas-surface interactions is presented. The cleaning effect of ultrasound and its surface activation play an important role for the sonochemical enhancement of reactivity in chemical processes involving solid and liquid phases. So far, there have only been a few studies on the effects of surface acoustic waves on surface chemical reactions under high-vacuum conditions by the application of piezoelectric surface acoustic wave transducers. Very recently, metal films deposited between InterDigital Transducer (IDT) electrodes on a LiNbO3 substrate have shown a significant inerease in catalytic activity during surface acoustic excitation and Edge-Bonded Transducers (EBT) with a metal single crystal as a substrate have been used to acoustically influence the rate in the oscillatory reaction for CO oxidation. Tunable narrowband surface acoustic excitation is anticipated to be an efficient route to control catalytic processes, and in our work this approach is being used to investigate the physical basis of this process.

Scanning acoustic force microscope measurements on grating-like electrodes

Abstract: Grating-like metal electrodes supplied with high- and low-frequency voltages were investigated by a Scanning Acoustic Force Microscope (SAFM). On piezoelectric LiNbO3, these electrodes form an interdigital transducer which generates surface acoustic waves according to the charge distribution on its electrodes when excited at a transducer's passband frequency. The influence of surface deformation and of surface charges on the cantilever deflection of the SAFM in contact and non-contact mode was systematically studied. Comparing the images of the electrodes which were prepared on piezoelectric and dielectric substrates, surface deformation and charge distributions were qualitatively separated.

Study on Power Durability of Ti-Containing Al Surface Acoustic Wave Electrodes, Using Interdigitated Interdigital Transducer Filters

Abstract: The power durability of Al-0.6 wt%Ti electrodes in 900 MHz interdigitated interdigital transducer surface acoustic wave (IIDT SAW) filters was investigated through accelerated time-to-failure (TF) tests in relation to grain sizes and annealing, and was further compared with that of pure Al, Al-0.5 wt%Pd and conventional Al-1.1 wt%Cu electrodes. TF of the Al-0.6 wt%Ti electrodes in the IIDT filter is increased by reducing the average grain size and the standard deviation of the grain size. Annealing of Al-0.6 wt%Ti film, however, results in increase of the average grain size and decrease of TF. TF of Al-0.6 wt%Ti electrodes was the largest: much larger than that of Al-0.5 wt%Pd electrodes, having almost the same grain size and standard deviation as Al-0.6 wt%Ti electrodes, and nine times as large as that of Al-1.1 wt%Cu electrodes.

Manufacture of surface acoustic wave device

Abstract: PURPOSE: To realize high shape intensity and to reduce a crack generation rate at least concerning input/output electrodes. CONSTITUTION: A dummy electrode 66 is provided at a place which is on a straight line combining the input and output electrodes 36 and 38 and is near the outside periphery part of an IDT(interdigital transducer) forming face 24, and a dummy bump 62 is arranged on the dummy electrode 66. While ultrasonic vibration is impressed in the direction of combining the input and output electrodes 36 and 38, face down bonding is executed. Even if a crack is generated by the resultant of summation impressed to a chip 32 and ultrasonic vibration, the input and output electrodes 36 and 38 are prevented from being destroyed because the crack is generated at the dummy electrode 66. At the time of impressing ultrasonic vibration in a direction perpendicular to the straight line combining the input and output electrode 36 and 38, the dummy bump 62 and the dummy electrode 66 may be arranged at a place which is along the direction and nearer to the outside periphery than the other electrodes.

Piezoelectric saw resonators

Abstract: A single-chip piezoelectric resonator using SH type surface waves has an interdigital transducer 13, 14 formed on a piezoelectric substrate 12. The interdigital transducer is designed to have two or more resonance characteristics, for example, by using a pair of thinned-out comb-shaped electrodes with mutually interlocking fingers protruding towards each other. Such an interdigital transducer may be formed also by using a pair of comb-shaped electrodes with the lengths of their mutually pointing fingers varied. A trap circuit (Figs 11, 13, 15) with two sufficiently separated trap frequencies and improved attenuation characteristics at these two trap frequencies can be formed by two interdigital transducers of the kind described above on a single piezoelectric substrate so as to provide two resonant units (58, 59) each having two resonance characteristics.

Discrete Green Function Theory for Multi-Electrode Interdigital Transducers

Abstract: The paper describes the extended discrete Green function theory for the analysis of multi-electrode interdigital transducers having electrodes of unequal pitch and/or width. Such a configuration is effectively used to develop unidirectional transducers. First, the field distribution on double- and triple-electrode gratings is calculated by generalisation of Aoki and Ingebrigtsen's method. Then, the discrete Green function is derived by representing the total field as a sum of contributions from various grating modes. Finally, the impulse response model for transducers having various electrode configurations is derived from the discrete Green function.

Diamond-LiTaO3 surface acoustic wave device

Abstract: The present invention directed to a SAW device comprising a diamond layer and an LiTaO 3 layer, which can be operated at the frequency of 3 GHz or higher, with superior durability and less energy loss. The SAW device for 1st mode surface acoustic wave of a wavelength λ (μm) according to the present invention comprises: a diamond layer, an interdigital transducer formed onto the diamond layer, and a polycrystalline C-axis-oriented LiTaO 3 layer formed over the interdigital transducer; wherein the SAW device satisfies a relationship of 0.4≦kh 1 ≦1.2, where a parameter kh 1 is defined as kh 1 =2π(t 1 /λ), and t 1 (μm) is the thickness of the LiTaO 3 layer.

Longitudinal-mode leaky SAW resonator filters on 64/spl deg/ Y-X lithium niobate

Abstract: Y-parameter modeling is applied to obtain the frequency response of a first/third dual-mode longitudinally-coupled leaky-SAW (LSAW) resonator-filter on 64/spl deg/C Y-X LiNbO/sub 3/. Conventional driving-point and transfer admittance relationships for SAW filters are modified to incorporate the effects of LSAW reflection and bulk-wave scattering in the interdigital transducers and are expanded to include reflection gratings with shorted-metal strips. As inferred from experiment, the grating parameters incorporate a phase-shift term to relate the anomalous dispersion of shorted gratings, as well as a modified phase-slope parameter between input and output interdigital transducers (IDT's). Good agreement is obtained with experimental results published for 836.5 MHz two- and four-pole structures in the maximum-bandwidth configuration. >

Interdigital transducer for acousto-optic tunable filter on LiNbO3

Abstract: Interdigital transducers on X-cut Y-propagating lithium niobate generate parasitic Bleustein-Gulyaev waves which reduce the acoustic efficiency. An increased number of electrode pairs improves the efficiency and an AOTF driven by an RF electric power of only 6 mW can be realised.

Lithium niobate thin films deposited on silicon substrates and their SAW applications

Abstract: Lithium niobate has a number of attractive piezoelectric and ferroelectric properties that have been exploited for many applications. The main purpose of our work was to grow lithium niobate thin films on silicon substrates and make surface acoustic wave (SAW) devices. Theoretical curves of SAW properties of bulk crystals and films lithium niobate on silicon with a coating of silicon oxide were also obtained. The theoretical results include elastic wave properties (velocities and power flow angle) in lithium niobate bulk crystals and SAW properties (velocities and coupling coefficients). Thin films of lithium niobate have been deposited on Si (100) substrates (with SiO2 coatings) by rf magnetron sputtering. Lithium niobate film samples with very good transparency and uniformity were obtained. The film samples were structurally analyzed using Bragg x-ray diffraction (XRD). Lithium niobate XRD peaks for specific sputtering conditions corresponding to thin film orientation of (012), (104) and (110) ...

Surface acoustic wave device and communication device employing the surface acoustic wave device

Abstract: A surface acoustic wave device makes it possible to increase the electrode width without generating mass-electrical-loading and is capable of operating in a high-frequency band higher than or equal to the UHF band, and this surface acoustic way device may be used in a communication device to eliminate need for any down-converter which is indispensable to the conventional high-frequency communication device, and which is therefore capable of being manufactured at a reduced cost. The surface acoustic wave device is provided with an electrode structure meeting conditions represented by: s+m=(2n+1)L/(4k), where L is electrode period, not taking into consideration the polarity of an interdigital transducer, m is electrode line width, s is minimum electrode gap width, and n and k are natural numbers. The surface acoustic wave device is used as the demodulator of the communication device.

Finite element simulation of bulk elastic waves in piezoceramic transducers using interdigital electrodes

Abstract: Bulk waves can be created in a thin piezoelectric plate by applying an electrical signal to interdigital electrodes deposited on each side of the plate. These transducers can be used to generate ultrasonic bulk waves with a wide range of frequencies and amplitudes controlled by a number of electrodes and a delayed voltage independently applied to each electrode. The current work centers on feasibility study of damage detection via amplified ultrasonic signals generated by interdigital transducers. To this end, finite element simulation of the generation and detection of bulk waves in piezoelectric substrates by means of interdigital transducers is presented and their potential application as probes in smart structures is also discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Excitation of ultrasonic Lamb waves in composite membranes

Abstract: The excitation of ultrasonic Lamb waves by an interdigital transducer in a composite plate consisting of a piezoelectric thin film deposited on a nonpiezoelectric membrane is analyzed using the Green's function method. The amplitudes of the generated waves are obtained in terms of the charge density on transducer electrodes. An electrostatic analysis that neglects piezoelectric coupling is used to relate this charge density to the voltage applied across the IDT. This is then used to calculate the input characteristics of the IDT. The characteristics of Lamb wave devices fabricated on a zinc oxide-on-silicon nitride membrane are measured and compared with theoretical calculations. It is shown that strong internal reflections are inherently present in an IDT fabricated on thin plates. A knowledge of these is essential in order to correctly calculate the characteristics of the IDT. It appears that the internal reflections can be utilized to realize unidirectional transducers for Lamb waves.

Spatial spectrum of electric charge on planar array of metal strips

Abstract: There is a known difficulty in the effective evaluation of electric charge distribution on multi-electrode interdigital tranducers of surface acoustic waves. The spatial spectrum of this charge distribution determines the transducer frequency response. A method of solving this problem, that directly yields this spatial spectrum, is proposed. It can also be exploited in the evaluation of the total electric charge on strips having arbitrary electric potentials.