Showing papers on "Interdigital transducer published in 1988"

Suppression of bulk-scattering loss in SAW resonator with quasi-constant acoustic reflection periodicity

Abstract: The author proposes a SAW (surface acoustic wave) resonator structure which suppresses the bulk-scattering loss for a high reflectivity resonator. The approach uses an effective configuration to cancel the scattered radiation bulk waves from the GRs (grating reflectors) and the IDT (interdigital transducer) simultaneously. It consists of an IDT and metal-strip GRs, which are of the same material and which have the same thickness. The distance between the IDT and the GR is set to be a half-wavelength and the pitch for the IDT electrodes is slightly shortened to tune to the resonance condition. The structure realizes quasiconstant acoustic reflection periodicity (QARP) all over the resonator. The QARP structure was shown to suppress the mode conversion loss and to improve the resonator Q-factor. Experimental results provide that the QARP structure led to a two-fold improvement of the Q-factor for the high reflectivity resonator. Furthermore, theoretical analysis also proved that the scattered bulk waves were suppressed to less than 1/100 in the QARP-structured SAW resonator. >

Cure monitoring apparatus having high temperature ultrasonic transducers

Abstract: An apparatus for monitoring the curing of a fiber reinforced composite plastic which is cured at temperatures of the order of 350° C. and an ultrasonic transducer assembly useful in the apparatus. The transducer assembly comprises a lithium niobate piezoelectric element having anisotropic coefficients of thermal expansion which is mounted on a metal base of the transducer assembly by means of a layer of structured copper. The structured copper is thermo-compression diffusion bonded to the lithium niobate element and to the metal base, and is compliant in a transverse direction to compensate for differential thermal expansions while affording good electrical and thermal conductivity and good acoustic coupling between the lithium niobate element and metal base.

The scattering of surface acoustic waves by electrical effects in two-dimensional metal film structures

Abstract: A theory is presented for the scattering of surface acoustic waves by electrical effects in thin metal films of arbitrary shape on the surface of a piezoelectric material. A Green's function approach is used, and an expression for the two-dimensional Green's function appropriate to the problem is given. General expressions are obtained for the far-field radiation pattern and for the response of an interdigital transducer to a single scatterer. Expressions for the reflection and velocity perturbation due to periodic arrays of scatterers are also presented. Good agreement is found when the theoretical predictions are compared with a wide range of experimental results on lithium niobate. >

PVDF transducers generating Scholte waves

Abstract: We show that Scholte waves, propagated at a water/silica interface, may be generated by an interdigital transducer using a thin film of polyvinylidene fluoride as piezoelectric material.

Surface acoustic wave device having apodized transducer provided with irregular pitch electrode group

Abstract: A surface acoustic wave device characterized in that in addition to linear first bus-bar electrodes which connect in alignment the edges of the same potential electrodes of interdigital electrodes, second bus-bar electrodes are provided which connect the same potential electrodes in the vicinity of the overlapping positions. Also disclosed is a surface acoustic wave device characterized in that the metalized ratio g/p, which is the ratio of the width of an electrode and the intercentral distance between the adjacent electrodes in an irregular pitch electrode group, is varied between 0.1 to 0.4 or between 0.6 to 0.9.

Accurate computation of apodized SAW transducer capacitances

Abstract: The passband slope of a SAW (surface acoustic wave) filter with large fractional bandwidth critically depends on the value of the operating capacitances of the input and output interdigital transducer (IDT) To reduce the number of design cycles required to achieve a flat passband response, a program for the computation of all relevant contributions to the IDT capacitance was developed For the analysis of the apodized transducer, a track division approach is used The capacitance contributions from the different tracks are computed by means of an interfinger nodal capacitance matrix As this matrix is calculated from the Green's function of the boundary value problem, the presence of the grounded back-plane and any nonconductive adhesive is automatically taken into account The operating capacitances of two different SAW filters with center frequencies of 70 MHz and 140 MHz fabricated on YZ-LiNbO/sub 3/ were calculated and compared to measurements >

Light beam deflector/modulator

Abstract: A waveguide-type light deflector or modulator includes an optical waveguide for guiding a light beam therethrough along a light path, and an interdigital transducer for generating surface elastic waves in the optical waveguide to diffract the light beam and for propagating the surface elastic waves in opposite directions across the light path, the interdigital transducer being transversely disposed to the light path in a substantially central position in the light path. In the light deflector, an alternating voltage with a continuously varying frequency is applied to the interdigital transducer to enable the surface elastic waves to continuously diffract and deflect the light beam. In the light modulator, the application of an alternating voltage to the interdigital transducer is controlled to vary the diffraction efficiency of the light beam, thereby to modulate the light beam.

Acousto-optical device with lithium tantalate transducer

Abstract: An acousto-optical device includes a solid state substrate having optical characteristics affected by an acoustic wave in the substrate, and a Z-cut lithium tantalate transducer coupled to the substrate for inducing the acoustic wave. Lithium tantalate provides the transducer with a coupling coefficient and acoustic impedance mismatch which generate a very high finesse acoustic standing wave within the substrate. The lithium tantalate also provides low shear wave components with relatively high manufacturing tolerances. The acousto-optical device with a lithium tantalate transducer is also utilized as a high Q modelocker in a laser capable of producing short pulses of laser light.

Surface acoustic wave resonator and method for adjusting its resonance frequency

Abstract: PURPOSE: To easily adjust the resonance frequency of a surface acoustic wave resonator by providing an interdigital capacitor to the said surface acoustic wave resonator and cutting off the electrode of the said interdigital capacitor little by little with a laser beam. CONSTITUTION: An interdigital capacitor 6 is formed on a said dielectric sub stance. In this case, the said interdigital capacitor 8 is provided to the lower part of the dielectric substance in which no drive electrode 2 and reflecting electrode 3 is provided and the direction of the interdigital electrode is arranged at a right angle to the direction of the drive electrode 2 and the reflection electrode 3. Then one electrode of the interdigital capacitor 6 is connected to one electrode of the drive electrode 2, the other electrode of the interdigital capacitor 6, the other electrode of the drive electrode 2 and a leadout wire 5 to be connected to an external circuit are provided. Then the area of the opposite electrodes is changed by cutting off the opposed electrodes of the interdigital capacitor 6 little by little thereby varying the static capacitance. COPYRIGHT: (C)1990,JPO&Japio

Acoustic charge transport processor

Abstract: An acoustic charge transport (ACT) device is easily constructed to provide for variable carrier frequency operation or, alternatively, for variable time delays. Variable carrier frequency operation in an ACT device is achieved by incorporating a two dimensional dispersive transducer array which has an interdigitated finger arrangement. This array has a graded periodicity or finger spacing that varies along the length of the array and also has the fingers placed at a 45 degree angle with respect to the length of the array. Because of the varying spacing of the electrode fingers, different spatial regions in the piezoelectric substrate are preferentially excited reflecting the presence of specific frequency components in an applied input signal. A variable time delay is similarly achieved in an ACT device by incorporating a two dimensional interdigital transducer array having fingers with a graded periodicity. The finger spacings in this transducer array are placed at a 90 degree angle with respect to the length of the array. By simply changing the frequency of the input signal in the selected ACT device, variable carrier frequency operation and variable time delays are provided.

New surface acoustic wave interdigital transducers with narrow electrode gaps

Abstract: A surface acoustic wave (SAW) interdigital transducer (IDT) and a unidirectional transducer (UDT) are described. A description is given of the lift-off etching method and lift-off anodic oxidation fabrication method techniques used to get controllable narrow gaps between electrodes with good insulation. Experimental results show a 7.2-dB insertion loss with ripple of 1.2 dB for a conventional IDT, and directivities of 6-dB/transducer at 438 MHz for a floating-electrode-type unidirectional transducer (FEUDT) and 17 dB/transducer for its second harmonic at 868.5 MHz. A minimum insertion loss of 3.6 dB for a low-loss group type unidirectional transducer (GUDT) filter at 477 MHz were obtained. >

Sound velocity measurements in thin films

Abstract: The authors have developed a novel technique for measuring the phase velocity of elastic waves in self-supporting thin films. One edge of the film is fixed to an interdigital transducer (IDT) acting as a transmitter, while another IDT, the receiver, moves freely above the film. The coupling between the receiver and the film is made through a liquid bond. This allows a continuous variation of the path length, and the resulting change in phase and amplitude of the received continuous-wave (CW) signal permits a simultaneous and accurate measurement of the phase velocities of the different vibrational modes present in the foil. >

Anisotropy dependence of the focused field radiated into a piezoelectric half‐space by an interdigital transducer

Abstract: Bulk waves radiated into an anisotropic half‐space by an interdigital transducer are studied theoretically. The mechanical displacements of excited waves are obtained by asymptotic evaluation of an integral whose singularities give rise to both Rayleigh surface waves and angularly focused bulk waves. By applying the analysis to singly rotated Y cuts of quartz with propagation normal to the x axis, it is shown that the orientation and width of the main lobe are very sensitive to frequency and crystal orientation.

Analysis of planar bulk acoustic wave devices

Abstract: The bulk acoustic waves launched in a piezoelectric crystal by an interdigital transducer, considered earlier as a spurious response in SAW devices, are now usefully employed in planar bulk acoustic wave (BAW) devices. This paper presents the results of a theoretical analysis of bulk wave response in a material. The analysis enables one to design BAW devices with a more desirable response than those obtained so far.

Study of SAW pulse compression using 5*5 Barker codes with quadraphase IDT geometries

Abstract: A theoretical and experimental study of pulse expansion and compression is reported for a 100-MHz SAW (surface acoustic wave) quadraphase code generator with 1250 IDT (interdigital transducer) fingers on ST-quartz as derived from a combined 5*5 Barker sequence. Techniques are also examined for increasing the peak-to-sidelobe ratio of the compressed pulse, using a series SAW suppression filter whose IDT apodization is derived from the inverse spectral ripple factor of the combined Barker code. >

Method and apparatus for phase measurement of signals at a measuring point by an unmodulated particle beam

Abstract: In the method and apparatus for the phase measurement of arbitrary signals at a measuring point, for example, of surface waves on piezoelectrical substrates, the surface waves are excited on the surface of a specimen having piezoelectrical features. The measuring point on the specimen surface is scanned by a particle beam and a secondary electrical signal at the measuring point is supplied to an evaluation circuit via a detector. A phase detector within the evaluation circuit is operated in a linear region of its output characteristic curve with the use of a feedback. This makes it possible to keep the phase at the phase detector constant. The phase of the signal to be examined, for example, of the surface wave, which is produced at a interdigital transducer is influenced due to the feedback.

Process for producing an opto-electronic transducer with an integrated connection element for an optical waveguide, the opto-electronic transducer produced by the process and an opto-electronic measured-value arrangement with an opto-electronic transducer

Abstract: The invention relates to a process for producing an opto-electronic transducer with an integrated connection element for an optical waveguide, the opto-electronic transducer produced by the process and an opto-electronic measured-value arrangement with an opto-electronic transducer. The surface of the opto-electronic transducer containing the optical measured-value pick-up surface is scanned in a grid-like manner while measuring the optical conductivity. In the region of maximum optical conductivity, a capillary-like connection element is then connected to the opto-electronic transducer.

Method and device for measuring mass flow of gas

Abstract: A surface acoustic wave device for measuring the mass flow rate of a gas includes a surface acoustic wave delay line formed of a piezoelectric substrate and having a temperature coefficient of delay on the order of 10 / DEG C The substrate has disposed thereon a transmitting and a receiving interdigital transducer, the transducers being configured to have an operating frequency in the range of from 10MHz to 1000MHz That portion of the substrate located between the transducers defines a propagation region and has a medium deposited thereon for absorbing a portion of the acoustical and/or electrical energy flowing thereacross This absorbed energy increases the temperature of the propagation region over that of the surrounding ambient A mass flow of the gas across the sensor will decrease its temperature and result in an upward shift in the resonant frequency A suitable amplifier and resonant frequency detector may be coupled to the sensor for detecting the change in resonant frequency, thereby permitting mass flow rate measurement

Surface acoustic wave device

Abstract: FIELD: radio electronics; acoustoelectronic acoustic-surface-wave frequency selectors. ^ SUBSTANCE: device has two input and two output terminals and piezoelectric acoustic duct carrying on its working edge first and second interdigital electrode sets whose single-phase electrodes are interconnected by means of first, second, and common power buses. Device also has additional interdigital transducer whose first bus is electrically connected to first input and first output terminals and its second bus is connected to common power bus. Second input and second output terminals are connected to first and second power buses. Electrode number for additional interdigital transducer, period and aperture for first and second interdigital transducers are chosen to ensure that inductive reactances of additional interdigital transducer and capacitive reactances of first and second interdigital transducers will provide for matching input and output impedances. Such layout structure will enable reduction of insertion loss to a level of 1 - 2 dB. ^ EFFECT: reduced insertion loss without increasing size of device. ^ 1 cl, 2 dwg

Calculation of Interdigital Transducer Interaction with SAWs and BAWs

Abstract: Since the interdigital transducer (IDT) was used by WHITE and VOLTMER /1/ in 1965 to excite surface acoustic waves (SAWs) on plane piezoelectric substrates, signal processing devices based on this effect have evolved to a high degree of maturity and are described comprehensively in the book by MORGAN /2/. These devices are fabricated in a one step planar metal layer technology and consist mainly of launching (L) and receiving (R) — IDTs whose structure determines the electric filter characteristic. Simple physical reasoning shows, that the IDT’s SAW impulse response h(t) in a first approximation is given by its structure (i.e. the finger arrangement and mutual finger overlap, called apodisation). Fourier transform (FT −) yields the transfer function \(\bar H\)(w) of the IDT: $$\bar H\left( w \right) = F{T^ - }\left( {h\left( t \right)} \right).$$ (1)

A study of acoustoelectric effect in GaAs by fabricating interdigital transducer using electron beam lithography technique

Abstract: Transverse acoustoelectric voltage (TAV) of Te-doped GaAs and n-GaAs/SI GaAs samples with photon energy and bias voltage is demonstrated GaAs electronic properties were investigated using a surface acoustic wave (SAW) technique The TAV was monitored across the GaAs sample by fabricating the interdigital transducer directly on the GaAs surface using electron beam lithography In the processing, to protect the surface from contamination, the metal lift-off technique is also used The TAV is developed due to the nonlinear interaction between the electric field accompanying SAW, and the free carriers near the GaAs surface The TAV spectra are obtained to determining the bandgap energy and the Te-level which is observed at 300 K It is also noticed that the TAV amplitude changes with bias voltage under the room illumination However, when the illumination is turned off, the TAV does not change with bias voltage >

Surface acoustic wave device

Abstract: PURPOSE:To provide a function varying the device performance by forming an insulation layer covering the upper face of the electrode in a surface acoustic wave (SAW) element where an interdigital transducer (IDT) electrode is arranged on the surface of a piezoelectric substrate and forming an electrode clipping the said electrode between the rear side of the piezoelectric substrate and the surface of the insulation layer. CONSTITUTION:An insulation film 4 (standardized film thickness: SiO2 film having a film thickness/electrode pitch of 0.042-0.161) is formed on the upper face of an IDT electrode 2 and a reflector 3 by the sputtering technology. An aluminum is vapor-deposited to the upper face of the insulation film 4 and the lower face of the piezoelectric substrate 1 and the top electrode part 5 and the under electrode part 6 are provided. An oscillator circuit is connected to a resonator terminal of a SAW device shown in figure and a DC voltage is applied between the top electrode 5 and the under electrode 6 to measure the oscillating frequency at that time. Then the change in the oscillating frequency at the DC voltage of 1000--1000V is 60--80PPM with respect to the frequency with no voltage applied.

Analysis of piezoelectric ceramic length-expansion-mode resonators using interdigital electrodes for both poling treatment and ac excitation

Abstract: When interdigital electrodes set on the surface of a rectangular piezoelectric plate are used for poling and ac excitation, a length-expansion-mode resonance in the Lame-mode system alone is emphasized. However, this does not occur easily in conventional length-expansion-mode resonators having a uniform poling across the thickness and electrodes on the entire surface. The proposed method offers a resonator with very little spurious oscillation in this mode. To obtain a guideline for designing interdigital electrodes, the relationships between the width of electrodes, the period of electrodes and the capacitance ratios were analyzed theoretically in detail by using conformal mapping. The strength and direction of the dc electric field of this type of resonator at a poling state vary with positions, since the poling treatment is also carried out with interdigital electrodes, i.e., its dielectric constant, piezoelectric constant, and elastic constant vary significantly with positions. In this analysis, the distributions of these constants in various positions were considered by using the dependence of the poling electric field obtained experimentally, and they are not averaged. The results of the analysis agree well with the experimental values. The characteristics of two configurations were compared: a piezoelectric longitudinal coupling with electrodes set rectangularly to the direction of vibrations; and piezoelectric transverse coupling with electrodes set in parallel to it.

Oberflaechenwellen interdigital transducer and oberflaechenwellen-filter with symmetrical or asymmetrical be predetermined transmission characteristic between input and output

Abstract: Surface wave interdigital transducer and filter with predetermined transfer characteristic with respect to symmetry The transducer (43, 53) is a split-finger transducer in which pairs of split fingers (36) are replaced by a number of single fingers (35)

Surface acoustic wave gas flow rate sensor

Abstract: A surface acoustic wave device for measuring the mass flow rate of a gas includes a surface acoustic wave delay line formed of a piezoelectric substrate and having a temperature coefficient of delay on the order of 10 / DEG C. The substrate has disposed thereon a transmitting and a receiving interdigital transducer, the transducers being configured to have an operating frequency in the range of from 10MHz to 1000MHz. That portion of the substrate located between the transducers defines a propagation region and has a medium deposited thereon for absorbing a portion of the acoustical and/or electrical energy flowing thereacross. This absorbed energy increases the temperature of the propagation region over that of the surrounding ambient. A mass flow of the gas across the sensor will decrease its temperature and result in an upward shift in the resonant frequency. A suitable amplifier and resonant frequency detector may be coupled to the sensor for detecting the change in resonant frequency, thereby permitting mass flow rate measurement.

Filter zur unterdrueckung von oberflaechen-interferenzen fuer satellitenkommunikations-empfaenger Filter to suppress surface until-interferences for satellite communication-empfaenger

Abstract: A surface acoustic wave (SAW) filter for suppressing surface to surface interference for a satellite communication receiver comprises two input (IDT1 and IDT2) and one output (IDT3) interdigital transducers constructed and arranged on a common piezoelectric substrate. The widths of the adjacent portions of electrodes and the spaces between the electrodes of the input interdigital transducers are adjusted based upon the principle of a transversal filter so that the frequency response of the input interdigital transducer (IDT1) has a predetermined pass band width and the transducer (IDT2) has a reduced gain in a frequency range which may include an interference signal. A switch SW switches the input signal into either of the transducers IDT1 and IDT2.

Design of sound source with fresnel‐zone pattern and its field analysis

Abstract: When an interdigital transducer (IDT) is loaded with a liquid, an acoustic beam can be excited in the liquid. To focus this acoustic wave in the liquid, the authors have used an IDT that is divided in a Fresnel zone type in the direction of the electrode aperture. From a theoretical calculation of the focused acoustic field generated by the Fresnel zone IDT, it is found that the point of maximum sound pressure is closer to the electrode than the designed focal point. To find the cause of this discrepancy, the acoustic field excited by the Fresnel zone source is analyzed. It is found that a modification in the design model of Fresnel zone IDT's is needed due to the difference between the two- and three-dimensional fields. A new optimum design method is proposed in which the focal point obtained from field analysis and that obtained from the electrode design model coincide.