Showing papers on "Interdigital transducer published in 1983"

Acoustic charge transport device and method.

Abstract: Method and device for delaying an electrical signal, the method and device being useable in various signal processing applications. A buried channel (41) is formed by disposing a portion of a layer of piezoelectric semiconductor material (40) between confining layers (50, 30). A surface acoustic wave is established in the piezoelectric semiconductor material via an input transducer (55). Majority carriers are depleted from the channel, and an electrical signal is injected into the channel via an interdigital transducer (55). A delayed version of the electrical signal, which had been carried along by the surface acoustic wave, can then be extracted from the channel via an output diode (71).

Elastic surface wave device

Abstract: To eliminate disturbance signals caused by the reflection from the unitary stem areas of comb-like electrodes of an interdigital transducer in an elastic surface wave device, the edges of the unitary stem areas perpendicular to the surface wave propagating direction includes at least one pair of partial edges, the positions of the partial edges in each of the at least one pair of partial edges differ by (2n+1)·λ/4 from each other in the surface wave propagating direction, and the lengths of the partial edges in the each pair are equal to each other, where n represents zero or a positive integer and λ represents the wavelength of the elastic surface.

High speed receiver designs based on surface acoustic wave devices

Abstract: The principles of operation and several types of surface acoustic wave devices are reviewed. One device, the interdigital transducer device, can accomplish matched filtering for complex bandwidth-efficient phase modulations. Data speeds in excess of 120 Mb/s are accomplished with existing thin film lithography. Filters are cheap and small, and show little mismatch to the desired response. A number of receiver designs are proposed that are based on these filters. A bank-of-matched-filters approach seems superior to the Viterbi algorithm at high speeds.

An integrated-optic Fourier processor using an acoustooptic deflector and Fresnel lenses in As 2 S 3 waveguide

Abstract: An integrated-optic Fourier processor consisting of an acoustooptic (AO) deflector and graded-index Fresnel lenses in an As 2 S 3 waveguide on a SiO 2 /Si substrate is proposed and the prototype device is demonstrated. For the interdigital transducer (IDT) for surface acoustic wave excitation, a two-stage array of uniform-period IDT and a chirped IDT using a ZnO piezoelectric film are adopted. High efficielicy and low drive power, as well as wide bandwidth of one octave in the device with a chirped IDT, have been obtained and the Fourier transformation function has been confirmed.

Poling of Ferroelectric Crystals by Using Interdigital Electrodes and Its Application to Bulk-Wave Transducers

Abstract: The planar transducer, which uses interdigital electrodes on the surface of a ferroelectric ceramic block for both poling and excitation, can generate bulk waves propagating in the direction normal to the surface. If it is possible to fabricate a similar transducer on a ferroelectric single crystal, such as LiNbOg and LiTa03, It would be useful as a high-frequency bulk-wave transducer for various acousto-optic devices, because of its widebandwidth and bording-less structure. In this paper it is demonstrated that an array of alternating polarity antiparallel domains can be formed under the surface of a LiTa03 crystal by cooling the crystal through the Curie temperature under ar. appiied DC vcltage to interdlgital electrodes on the crystal surface. The characteristics of planar transducers exploiting the domain array are also described.

Multi-frequency ultrasonic transducer

Abstract: An ultrasonic transducer consisting of three piezoelectric element couples sandwiched between four metal terminals. Each piezoelectric couple has two piezoelectric elements separated by an electrode. The piezoelectric couples and the metal terminals are secured together by a bolt. The transducer exhibits various combinations of resonant frequencies in its impedance-frequency characteristic as determined between various combinations of the electrodes and terminals.

Propagation of Transverse Surface Acoustic Waves in Rotated Y-Cut Quartz Substrates Under Heavy Periodic Metal Electrodes

Abstract: Abstmct-A theory of the propagation of transverse surface acoustic waves on a piezoelectric substrate with heavy periodic metal electrodes on the surface is presented. The mechanical properties of these electrodes are assumed to be nonnegligible. Dispersion relations for waves near the stopband of the periodic electrode array are analyzed. It is found that the mass of the electrodes exerts a considerable effect on the shape and mutual positions of the stopbands for short-circuited and electrically isolated electrodes. The discussion is based on an approximation for the effective surface impedance that relates the amplitudes of the electric and elastic fields observed at the surface of a piezoelectric substrate. The parameters of this approximation are given for rotated Y-cut quartz substrate. The theory presented can readily be generalized to the case of Rayleigh surface waves.

High electromechanical-coupling coefficient surface acoustic wave device

Abstract: A high electromechanical-coupling surface acoustic wave device has a lithium niobate rotated Y-cut crystal as a piezoelectric substrate, and a thin high-density film formed on a predetermined portion of the lithium niobate rotated Y-cut crystal which includes at least a propagation path along which the surface acoustic wave propagates. A Love wave propagates in the thin or thick high-density film on the surface of the lithium niobate rotated Y-cut crystal substrate, so that the electromechanical coupling coefficient of the thin film can be improved, and spurious response caused by a Rayleigh wave can be eliminated.

Group-type unidirectional SAW devices employing intra-transducer reflector banks

Abstract: A novel interdigital transducer is described which employs intratransducer reflector banks to achieve unidirectionality, and whose fabrication requires a single photolithographic process.

Coupling of interdigital transducer to plate modes in a slotted acoustically-thin membrane

Abstract: Piezoelectric coupling with an interdigital transducer (IDT) to plate modes in a composite ZnO-SiO 2 -Si membrane that is thinner than an acoustic wavelength has been examined for possible use in forming on-chip filters or resonators. Tests at 80 MHz on a composite membrane approximately 45 µm thick with IDT's having a 76 µm period indicates preferential coupling to the lowest quasi-symmetric plate wave having a phase velocity roughly 60% higher than that of the ordinary surface-acoustic-wave (SAW) on the unthinned portion of the same silicon wafer. Results are presented for a resonator made on such a structure in which end reflectors are single slots etched in the membrane. Numerical calculations confirm the observation and reveal that the electromechanical coupling coefficient is 1.4% as compared with 0.1% for ordinary SAW's on semi-infinite substrate.

Low reflectivity surface acoustic wave transducers on GaAs

Abstract: Experimental results are presented for fabrication and metallization techniques which achieve low reflectivity surface acoustic wave (SAW) interdigital transducer operation on GaAs. The transducer structures considered are single finger pair, quarter wavelength designs with chrome/aluminum/chrome (surface), aluminum (recessed) or gold‐germanium/nickel/gold (surface) metallized electrodes which were fabricated directly onto a semi‐insulating GaAs substrate. Triple transit signal suppression greater than 53 dB for the recessed aluminum metallization and greater than 62 dB for the Au‐Ge/Ni/Au metallization has been achieved for test transducers operating at 159 MHz, compared to typically 30–35 dB for Cr/Al/Cr metallizations. These low reflectivity transducers provide the means for reducing spurious signal responses within monolithic programmable GaAs signal processors and for achieving higher Q performance of SAW resonator filters fabricated on GaAs substrates.

Surface acoustic wave device having interdigitated comb electrodes weighted for odd/even response

Abstract: A surface acoustic wave device disclosed herein has input and output electrodes (21, 22) one of which (21) comprises a first interdigital electrode (23) defining even components of a frequency response and a second interdigital electrode (24) defining odd components thereof, the second interdigital electrode (24) being disposed outside the envelope of the first interdigital electrode (23). A portion of the second interdigital electrode (24) is disposed within a non-overlapping region of the first interdigital electrode (23), that is a region outside the envelope of the first interdigital electrode (23) and especially a region environed with a straight line running through the top of the envelope in a direction parallel with the propagating direction of the surface waves.

Unidirectional transducer for a surface-acoustic-wave device and a method of making same

Abstract: A surface-acoustic-wave device includes a transducer in which three transducer electrodes are provided on a non-piezoelectric or piezoelectric substrate with 0°, 120° and 240° phases, and one of the leading electrodes connected to one of the transducer electrodes extends along the surface of a piezoelectric layer provided on the substrate.

Two Dimensional Mapping of SAW Propagation Constants by Using Fresnel-Phase-Plate Interdigital Transducer

Abstract: The methods of measuring the acoustic properties of solids by using the acoustic beams from interdigital transducers (IDT) is described. An IDT can radiate acoustic waves into liquid in oblique directions with respect to the substrate surface, and the wave fronts can be arbitrarly controlled by designing the IDT shape. One IDT couple is used to measure the acoustic properties of a solid sample. In the present study, we show a new method for focusing the beam from an IDT and measuring the acoustic properties of solids. An interdigital electrode is divided into several sections, each of which is placed to form a one dimensional Fresnel phase plate (FPP) on a piezoelectric substrate. It has been found that the FPP IDT generates a converging beam onto a focal plane, and the present system is suitable for measuring the two dimensional variation of leaky SAW phase velocity on a sample surface.

Interdigital transducer with suppression of reflected interfering signals

Abstract: At the end of the other (transmitting) transducer (3) opposite to one (receiving) transducer (4), reflections of the generated (and received) surface wave occur which can superimpose strong interference signals on the useful signal. By means of the one or more additional fingers (10' with 10'', 11' with 11''...;40,41) added to this (respective) end in accordance with the invention, such a reflection interference signal can be prevented when the distance is dimensioned to be lambda o/4) in accordance with the invention.

Surface acoustic wave multiplex mode filter

Abstract: PURPOSE:To form a BPF with high Q and stability at high frequencies, by acoustically coupling two surface acoustic wave resonators CONSTITUTION:Two surface acoustic wave resonators are formed by arranging two multipair interdigital transducer electrodes 12 and 13 adjacently in series along the X axis (direction of propagation of surface acoustic waves) on a piezoelectric substrate 11 The resonance frequency of the resonators set identical When the two resonators are acoustically coupled and resonated, two oscillatin modes, objective mode and antiobjective mode are generated When a filter is formed by using the resonance frequency of both the modes, the difference between both the resonance frequencies is almost a half-amplitude level of the band width of a BPF Thus, the BPF with high Q and stability can be formed at high frequency bands

Acousto-optic transducer

Abstract: A spectrum analyzer incorporates a 36° Y cut lithium niobate Bragg cell provided on one face with an interdigital transducer. The 36° Y cut maximizes the ratio of quasi-longitudinal to quasi-shear wave piezoelectric coupling with the interdigital transducer and thereby minimizes the output of spurious signals from the analyzer. In a preferred embodiment the Bragg cell comprises two lithium niobate crystals bonded by a metal (preferably gold) film, the crystal attached to the transducer being 36° Y cut and the other crystal being cut so as to maximize acousto-optic coupling.

Measurement of Elastic Anisotropy of Solid Using an Interdigital Transducer for Underwater Ultrasonic Wave Excitation

Abstract: One interdigital transducer couple (IDTs) on a piezoelectric substrate has been used to investigate the acoustic properties of anisotropic materials. An IDT can radiate underwater ultrasonic wave in oblique directions with respect to the substrate surface. When the acoustic beam is incident on the solid sample-water interface near the Rayleigh angle, the reflection field is equal to the superposed fields of the specular reflection and the reradiation from the leaky SAW excited on the sample. The velocity and the attenuation of the leaky SAW on the sample can be obtained from the measured trailing field due to the reradiation.

Reflection-compensated surface acoustic wave transducer

Abstract: An echo-compensating surface acoustic wave interdigital transducer in which the entire length of the end finger of the transducer at each end is connected directly or indirectly to at least one of the bus bars, the end finger extends only partially across the aperture of the transducer, and the space which is colinear with the end finger across the remaining portion of the aperture is not occupied by any surface-acoustic-wave-reflective structure. The end finger is substantially a quarter of an acoustic wavelength out of phase with the nearest interior finger with respect to an incident wave at the operating frequency of the transducer, so that the acoustic reflections of the end finger and the nearest interior finger are in phase-opposition to each other. In addition, the end finger spans one half of the transducer aperture, and is arranged to permit unobstructed acoustic reflection from the nearest interior finger over the other half of the aperture at one of the ends of the transducer, so that the resulting phase-opposed reflections are equal in amplitude in order to achieve mutual cancellation.

Surface acoustic device having multistrip coupler comprised of alternate coupled and uncoupled strips

Abstract: A surface acoustic wave device comprising a first set of interdigital electrodes that generate surface acoustic waves, a second set of interdigital electrodes that receive and convert surface acoustic waves into electrical signals, and an intermediate electromechanical coupling element provided therebetween. The coupling element comprises a plurality of parallel strips formed on the surface of a piezoelectric substrate such as to receive and change the direction of propagation of the surface acoustic waves, each of these parallel strips being spaced at a predetermined distance from each other and connected therebetween in a given manner to obtain suitable stopband characteristics.

Liquid crystal device having interdigitated electrodes

Abstract: This invention relates to a liquid crystal device applying an optoelectronic effect of liquid crystals. This invention aims at the provision of a liquid crystal device which is so constructed that; a transparent substrate having interdigital electrodes and a transparent substrate having an opposite electrode are disposed close to each other between two polarizers whose polarization axes intersect at a right angle with each other, so that both the electrodes are opposed to each other; a liquid crystal cell charging therein liquid crystal is disposed between both the transparent substrates so that the interdigital electrodes are arranged in parallel to the polarization axis of either one of two polarizers; the interdigital electrodes comprise a grounding electrode having a plurality of interdigital portions and a drive electrode positioned therebetween and having a width the same as that of one dot forming the ON and OFF conditions of the transmission light; and the drive electrodes are provided in plural rows, thereby having an extremely high contrast ratio for the ON and OFF conditions of the transmission light and responding at extremely high speed.

Studies concerning the dynamic range of the integrated optic spectrum analyser

Abstract: The work described in this thesis is concerned with some of the factors which can influence the dynamic range of the Integrated Optic Spectrum Analyser. Chapter 1 considers the various types of spectrum analyser device based on the interaction of acoustic waves with optical waves. The main features of the hulk acousto-optic spectrum analyser and the integrated optic spectrum analyser (IOSA) are considered. Two types of IOSA device are considered. The working of the IOSA device as well as its dynamic range is considered. In Chapter 2 the physical properties of Lithium Niobate are considered. The choice of Y-cut LiNbO3 as a substrate material for the IOSA is considered. The fabrication of titanium indiffused LiNbO3 optical waveguides are described. Chapter 3 considers the importance of in-plane light scattering in integrated optical devices and especially in the IOSA device. The study of in-plane light scattering in optical waveguides in relation to titanium thickness, diffusion time, diffusion temperature is considered. The evolution and disappearance of surface roughness during the diffusion process is considered and also the evolution of defects in the waveguides. Chapter h deals with the importance of surface acoustic waves (SAW) in signal processing devices. The interdigital transducer as a source for the excitation of SAW is considered. IDT delay line design parameters, fabrication and characterisation are described. Chapter 5 considers the theory of acousto-optic interaction. The dependence of the diffraction efficiency on various material parameters is considered. Experimental results obtained in the study of acousto-optic interaction are described. The discrepancy in the experimentally obtained results and the results already published by various authors is considered. Chapter 6 deals with the theory of multifrequency acousto-optic diffraction as given by D.L. Hecht. Experimental results (conforming to the phase matching conditions used for the theory) along with the difficulties involved in the observational of third order intermodulation signals are described. The experimentally obtained results for this thesis are compared with the theoretical results as well as with the limited results obtained by other authors. The dependence of the dynamic range of the IOSA on in-plane light scattering and third order intermodulation effects is considered. During work described in Chapter 5 and 6, changes in the waveguide index due to r.f. power were observed. In Chapter 7, the dependence of the changes in the refractive index of the waveguide on the r.f. power to the IDT and optical power in the waveguide is considered. From the study carried out in Chapter 7 it is concluded that changes in the index due to r.f. power at the IDT are due to the thermo-optic effect arising because of heat dissipation at the IDT. However the effect of the presence of optical power is probably not the photo-refractive effect. The main conclusions of the work done for this thesis are described in Chapter 8 along with suggestions for future work arising out of this study.

Discrete Frequency Bragg Deflector in 2 GHz Range Using ZnO/Sapphire Substrate

Abstract: A guided-wave acousto-optic (AO) Bragg deflector has been developed in 2GHz range using a single-crystal ZnO thin-film on a sapphire substrate. The ZnO thin-film was grown by RF magnetron sputtering and the propagation loss for TEo mode at 6328 1 wavelength was measured to be 1.2dB per cm. An electromechanica l coupling coefficient of 4% for t he ZnO film and a propagation loss of about 30dB per cm for the 1st-order mode (Sezawa mode) SAW were also measured. A withdrawal interdigital transducer (IDT) fabricated on thjs ZnO film has realized multiple discrete frequency responses with high Q factor. Preliminary experiments on the Bragg deflector have demonstrated discrete deflected light spots with a resolution of 3 MHz in the 2GHz range.

Planar Annular Surface Wave Transducer

Abstract: An annular surface wave transducer is a device where ingoing and outgoing radial surface waves, launched from concentric circular elec- trodes on the surface of a piezoelectric material, radiate acoustic energy into a liquid. The device has been used as a transducer for acoustic micro- copy, which uses the property that energy radiated into the liquid creates a focal spot on the device's symmetry axis. It is the energy radiated beyond this focal spot which is of interest in this paper. Analytical and experimental results showing the radiation pattern beyond the focal spot, and the effects of off-axis radiation on various imaging receivers will be discussed, with primary emphasis on axial energy variations in both intensity and beam width. Results from observing the device's unloaded surface with a laser imaging system will be given, and finally, the receiving characteristics of the annular surface wave transducer will be compared to a typical thickness transducer.

Electrode construction of surface acoustic wave resonator

Abstract: PURPOSE:To increase the impedance without deteriorating the Q of a titled resonator and the ratio of capacitance, by splitting a multi-paired interdigital transducer electrode into plural electrodes and connecting them mutually in series electrically. CONSTITUTION:The interdigital transducer electrode is cut off at the center and both are connected in series electrically. Since the parallel capacitance depends solely on the geometrical shape of the electrodes, the parallel capacitance is reduced to 1/4 of that of a conventional system. Since the ratio of the acoustic coupling between the split electrodes to the exciting strength between the electrode fingers is unchanged, the Q remains unchanged.

Surface acoustic wave multimode filter

Abstract: PURPOSE:To form a BPF which has high Q and high stability in a high frequency band, by acoustically coupling surface acoustic wave resonators, which have the same resonance frequency, on the same substrate. CONSTITUTION:On a substrate 11, numbers of couples of interdigital transducer electrodes 12 and 13 of surface acoustic wave resonators which have the same resonance frequency are arranged adjacently at right angles to the propagation direction of surface waves. When both kinds of electrodes are coupled together acoustically for resonance, two oscillation modes, or a symmetric mode and an asymmetric mode are generated at right angles to said propagation direction. When a BPF is formed by utilizing resonance frequencies of those two oscillation modes, the difference in resonance frequency is reduced to the half width of the passing band of the BPF. Thus, the BPF having high Q and high stability in a high frequency band is formed.