Abstract: According to this invention, a weighting transducer for a surface acoustic wave filter includes first, second, third bus electrodes, odd-numbered transducer fingers, and even-numbered transducer fingers. The first, second, third bus electrodes are formed on a piezoelectric substrate. The odd-numbered transducer fingers are formed on the piezoelectric substrate and consist of first transducer fingers connected to the first bus electrode and second transducer fingers connected to the second bus electrode and spaced apart from the first transducer fingers by a predetermined interval in the longitudinal direction. The even-numbered transducer fingers are formed on the piezoelectric substrate, connected to the third bus electrode, and consist of third transducer fingers overlapping the first and second transducer fingers.

Abstract: A fluid sensing device such as a Surface Transverse Wave device or a Love Wave device having controlled transfers of energy from a transduction surface of a piezoelectric substrate to a sensing surface and back to the transduction surface. A first wave-trapping structure adjacent to an input transducer tapers to provide a controlled diffraction of shear transverse wave energy to a second wave-trapping structure disposed on an opposite side of the piezoelectric substrate. The second wave-trapping structure interfaces with the fluid under test. The shear transverse waves are then recaptured by a third wave-trapping structure on the same surface as the first wave-trapping structure. The wave energy is then decoupled from the piezoelectric substrate. In the STW device, the wave-trapping structures are periodic fingers that are selectively varied in thickness or width or both. In the LW device, the wave-trapping structures are plates that each vary in thickness.

Abstract: A low-loss acoustic wave filter includes a piezoelectric substrate, a first strongly unidirectional acoustic wave transducer and a second strongly unidirectional acoustic wave transducer. Each of the first and second strongly unidirectional acoustic wave transducers are acoustically coupled to one another. Each of the first and second strongly unidirectional acoustic wave transducers further comprises an acoustic wave reflector and a weakly unidirectional acoustic wave transducer. The acoustic wave reflector and the weakly unidirectional acoustic wave transducer are coupled to the piezoelectric substrate.

Abstract: An electronic apparatus for receiving and filtering high frequency waves comprises a sequence of T electroacoustic transducers each having multiple interdigital electrode fingers and a centerline located equidistant between its outermost electrode fingers. For a centerline-to-centerline distance of a first adjacent pair of transducers D.sub.1, and centerline-to-centerline distances of other adjacent pairs of transducers D.sub.2 to D.sub.T-1, then at least some of D.sub.2 to D.sub.T-1 differ from D.sub.1 by a non-integral number of wavelengths. The transducer array is symmetrical about a centerline and the number of fingers in each transducer varies, with an input or output transducer closer to either end of the sequence having more fingers than a like kind transducer nearer the center.

Abstract: In a surface acoustic wave transducer including a substrate made of a piezoelectric material, an input side IDT structure having positive and negative electrodes arranged in an interdigit manner and floating electrodes arranged between successive positive and negative electrodes, and an output side IDT structure having positive and negative electrodes arranged in an interdigit manner and floating electrodes arranged between successive positive and negative electrodes, the electrodes of the input and output side IDT structures are arranged such that a surface acoustic wave propagates in one direction, distances between corresponding tracks in the input and output side IDT structures are linearly changed and lengths of these tracks are changed in accordance with a predetermined window function.

Abstract: The present invention provides an apparatus that is useful in obtaining blood flow information. The device includes a carrier that, in preferred embodiments of the invention, includes either a catheter or guide wire. The device further includes at least one transducer that is capable of generating and/or receiving an ultrasonic signal that departs or is received, respectively, by the transducer at an angle to the surface of the transducer that is exposed to the blood flow. One embodiment of the apparatus employs a transducer that is capable of generating a surface acoustic wave (SAW) that, upon contact with blood, is converted into a "leaky" wave. Another embodiment of the device employs a transducer that utilizes the grating lobe effect to transmit and/or receive ultrasonic signals at an angle to the surface of the transducer that is exposed to the blood flow.

Abstract: A surface wave transducer has measures for suppressing internal reflections on terminal fingers of a transducer having other transducer fingers, which are arranged interdigitally adjacent to the terminal fingers, which are arranged corresponding to a specified acoustic wavelength of the transducer at intervals specified by a predetermined scheme and which are designed with finger widths that are likewise specified by the predetermined scheme. On each end of the transducer only a plurality of terminal fingers, which are connected to one busbar of the transducer, are positioned deviating from the scheme for positionings and finger widths of the other transducer fingers and are positioned deviating in their finger strip width.

Abstract: A monolithic integrated circuit device combines integrated heterostructure acoustic charge transport (HACT) devices and heterostructure insulated gate field effect transistor (HIGFET) devices in a single structure in which the HACT and HIGFET layers are grown in as a contiguous composite heterostructure.

Abstract: An acoustic wave filtering apparatus includes an acoustic wave propagating substrate for supporting propagation of acoustic waves and a plurality of acoustic wave filters for filtering an electrical signal. Each of said plurality further comprises an input for supplying electrical input signals, an input unidirectional acoustic wave transducer for converting electrical signal energy into acoustic energy, an output unidirectional acoustic wave transducer for converting acoustic signals to electrical signals, and an output for combining and delivering electrical output signals to external electrical apparatus.

Abstract: A surface acoustic wave filter device includes a substrate which comprises quartz or the like piezoelectric having a small temperature coefficient and which is formed with unidirectional transducers of asymmetrical construction. A floating electrode is spaced from intermediate position between adjacent positive and negative electrodes which are arranged in interdigital manner, to effectively utilize a mechanical reflection caused by the floating electrode. In consideration of the sign and magnitude of the reflection factor of the floating electrodes, short-circuited electrodes only are used for the floating electrodes. The surface acoustic wave filter device has improved temperature characteristic, insertion loss characteristic and phase characteristic.

Abstract: A low-loss, wideband SAW transducer operating on a piezoelectric substrate with a longitudinal axis of propagation. The SAW transducer has a plurality of tapered interdigital electrodes that are mounted on the substrate transverse to the propagation axis. The electrode widths and spacings are constant along lines parallel to the axis and are tapered in the direction transverse to the axis. An acoustic-wave reflector having a plurality of elongated, tapered discontinuities or reflective fingers is located on the substrate adjacent one end of the transducer. The spacings and widths of the reflective fingers are similar to those of the electrodes, i.e., the finger widths and spacings are tapered in the direction transverse to the axis and are constant along lines parallel to the axis. Because of the taper, the fingers reflect wideband acoustic waves parallel to the axis.

Abstract: An inductive element for impedance matching comprises an acoustic wave propagating substrate and an acoustic wave transducer coupled to the acoustic wave propagating substrate. The acoustic wave transducer has an effective length L.sub.eff such that Le.sub.eff .gtoreq.C.sub.2 v.sub.a /f.sub.o k.sup.2, where C.sub.2 is a numerical factor such that C.sub.2 .gtoreq.2, v.sub.a represents an acoustic velocity, f.sub.o represents an acoustic wave transducer center frequency and k.sup.2 denotes an acoustic wave propagating substrate electromechanical coupling coefficient. Reflecting elements are provided on the substrate in the principal acoustic propagation directions to form a resonant acoustic cavity. The device exhibits inductive impedance and high Q over a significant frequency range in small physical size.

Abstract: A surface acoustic wave device in which a surface acoustic wave device element is arranged with interdigital electrodes on a piezoelectric substrate is packaged in a package provided in a metal pattern. Metal bumps are formed on a bonding pad section of the surface wave device element and the metal bumps are contact connected with the metal pattern of the package.

Abstract: A SAW reflector structure located between multiple interdigitated generator/receivers located on a piezo-electric substrate forming a ladder type SAW device is described. The reflector structure reduces both reflections due to mechanical-electrical loading from the physical presence of generator/receiver fingers without using a split finger arrangement as well as reflections due to the regenerated reflection from the generator/receiver. The reflector has a first acoustic phase center. The generator/receiver has a second acoustic phase center, a regenerated voltage coefficient of reflection, r.sub.e and a mechanical-electrical loading coefficient of reflection, r.sub.m. The reflector is used for simultaneously reflecting both regenerated and mechanical-electrical loading induced reflections from the generator/receiver. The reflector is sized for a strength of reflection equal to the square root of the sum of the regenerated and mechanical-electrical loading reflections squared.

Abstract: In a transducer for surface waves, an alternating succession of transmitter cells and reflector cells is used. The transmitter cells transmit surface waves in phase opposition, leftwards and rightwards. The reflector cells have a reflection coefficient that is in phase opposition between the left-hand side and the right-hand side. The waves transmitted by the transmitter cells interfere with the waves reflected by the reflector cells, destructively in one direction and constructively in the other direction. This enables the making of transducers with spacings equal to .lambda./4 and .lambda./6 only.

Abstract: A HACT device which propagates charge packets 21 along a charge transport channel 17 by a surface acoustic wave (SAW) 14 is provided with an interdigital electrode grid 30 disposed on the upper surface of the HACT, near the charge transport channel 17, having electrodes 30 spaced a distance of one-half wavelength of the SAW. A hold voltage Vh is applied across alternating electrodes to store (i.e., stop and hold) each charge packet. When a charge packet is to be released, the hold voltage Vh is removed and the electrodes 30 are shorted together or alternatively connected through a maximum allowable impedance, thereby allowing each charge packet 21 to be stored and released by the device without having the electrodes 30 absorb the SAW electric fields. Because the electrodes 30 are spaced one-half a SAW wavelength apart, the HACT memory can store each and every charge packet 21, thereby providing a Nyquist bandwidth device.

Abstract: A surface acoustic wave device which is a surface acoustic wave resonator utilizing an SH-type surface wave, wherein a resin layer made of a resin material in the form of gel or having a Shore hardness of not more than 30 is formed so as to coat at least an interdigital transducer formed on the upper surface of a piezoelectric substrate.

Abstract: A surface acoustic wave element has a low insertion loss in one direction and a wide band width. This surface acoustic wave element has first and second interdigital electrodes each having a thickness on a piezoelectric or electrostrictive substrate. In a first interdigital electrode for exciting a surface acoustic wave, positive and negative electrodes are alternately arranged such that their electrode widths and periods are gradually decreased in a direction of propagation of the surface acoustic wave. In a second interdigital electrode for receiving the surface acoustic wave, positive and negative electrodes are alternately arranged such that their electrode widths and periods are gradually increased or decreased in the direction of propagation of the surface acoustic wave.

Abstract: A surface-acoustic-wave device comprises a substrate of piezoelectric material providing for the propagation of surface acoustic waves along a channel formed on an upper major surface of the substrate, a plurality of interdigital electrodes provided on the piezoelectric substrate major surface in a row, in correspondence to the channel, such that the electrodes are aligned in the propagating direction of the surface acoustic waves, each of the plurality of interdigital electrodes having a first art connected to a bonding pad on the substrate for external electric connection and having a plurality of finger electrodes extending in parallel, spaced relationship with respect to each other in a direction transverse to and crossing the channel, and a second part separated from the first part and having a plurality of finger electrodes extending in parallel, spaced relationship with respect to each other and in a direction opposite to the direction of the finger electrodes of the first part and transverse to and cr

Abstract: Disclosed is a coplanar waveguide (CPW) which is connected directly into a balanced SAW transducer" via a tapered coplanar transmission line. Preferably, the CPW transition feeds directly into the "balanced transducer" such that the ground planes of the CPW taper directly into the outer (grounded) bus bars of the SAW transducer and the center conductor of the CPW feeds directly into the "hot" center electrode structure of the SAW transducer. This preferred structure is shown in FIG. 1. This balanced SAW transducer configuration provides better electrical shielding for lower electromagnetic feedthrough suppression and lower spurious signal levels. Moreover, the acoustic wave generated by this "balanced transducer" configuration provides a more uniform acoustic power distribution because the center conductor of the SAW transducer provides a waveguide effect wherein the acoustic energy tends to follow the slow velocity metal structure, thus forming an acoustic waveguide.

Abstract: A surface acoustic wave device comprises a piezoelectric substrate and a plurality of electrode fingers which are located on the piezoelectric substrate along the propagation direction of a surface acoustic wave. The electrode fingers are located on the piezoelectric substrate at a pitch of about 1.5.lambda.o/2 (where a symbol .lambda.o indicates a wavelength of a surface acoustic wave with a frequency equivalent to the center frequency of the surface acoustic wave device). The width of each of the electrode fingers is about 1.5.lambda.o/4. The electrode fingers are located on the substrate so as to be electrically independent of an external circuit and each other.Since the width of electrode fingers is about 1.5.lambda.o/4, the surface acoustic wave device can be produced without fine processing techniques.

Abstract: A chemical sensor (1) includes two or more pairs of interdigital electrodes (10) having different periodicities. Each pair is comprised of a first electrode (10a) and a second electrode (10b). The electrodes are patterned on a surface of a piezoelectric substrate (12). Each pair of electrodes may launch and receive various acoustic waves (AW), including a surface acoustic wave (SAW), and may also launch and receive several acoustic plate modes (APMs). The frequencies associated with each are functions of the transducer periodicity as well as the velocity of the particular AW in the chosen substrate material. An AW interaction region (13) exists between each pair of electrodes. Circuitry (20, 40) is used to launch, receive, and monitor the propagation characteristics of the AWs and may be configured in an intermittent measurement fashion or in a continuous measurement fashion. Perturbations to the AW velocity and attenuation are recorded at several frequencies and provide the sensor response.

Abstract: Two surface acoustic wave resonators are transversely formed with a minute spacing between them on a piezoelectric substrate. Said two surface acoustic wave resonators are oppositely formed to each other to become line-symmetry. Each of the surface acoustic wave resonator comprises an interdigital transducer and reflectors formed on its both sides. An input terminal and an output terminal are lead from the corresponding interdigital transducer. Between the input and the output terminals, an electrostatic capacity is bridged. The electrostatic capacity is formed on, for example, a piezoelectric substrate. In this case, the electrostatic capacity may be formed by alternately interdigitating each part of comb-like electrodes of the two interdigital transducers. Furthermore, the electrostatic capacity may be formed by alternately interdigitating both parts of the two reflector electrodes.

Abstract: A shear transverse wave device having transitions in the relaxation or tightening of wave trapping. Two embodiments are preferably utilized simultaneously. A first embodiment involves wave trapping fingers disposed within a propagation region between a transmitting and a receiving interdigital transducer. The wave trapping fingers provide a high width-to-spacing ratio of fingers proximate to the transducers and provide a lower ratio with approach to a center of the propagation region. The relaxed trapping reduces the adverse effects caused by surface perturbations, while the tight trapping at the transducers provides an efficient coupling of power to and from the device. The second embodiment is likewise concerned with decoupling of power. Absorptive film is placed at the opposed edges of the device to suppress spurious reflections from the edges.

Abstract: A passivation layer of dielectric material disposed on the top surface of the SAW device prevents the metallized transducer pattern on the piezoelectric substrate from being exposed to chemical attack. This layer also provides for improved metal acousto-migration resistance through the well-known mechanism of grain boundary pinning. The piezoelectric SAW device substrate includes a dielectric layer which is disposed along the surface over the transducer metallization. The piezoelectric substrate includes metallized regions on top of the dielectric layer which is disposed over the substrate surface and the SAW transducers thereon. These metallized regions form capacitors to the transducer busses and capacitively couple electrical input and output signals to the transducers from external electronic apparatus.

Abstract: A novel surface acoustic wave (SAW) element for use in a stabilized oscillator circuit capable of coupling directly to external circuitry includes a pair of opposed transducers formed on a surface of a piezoelectric crystal for launching surface acoustic waves into a resonant cavity formed by opposed reflectors on the crystal surface. The element is characterized by a supplemental transducer coupled to the cavity for directly providing external circuitry with signals corresponding to the resonant surface acoustic waves.

Abstract: An acoustic wave device comprises an acoustic wave transducer coupled to an acoustic wave propagating substrate. The acoustic wave transducer converts signal energy between electrical and acoustical forms. Acoustic reflectors are placed one on either side of the acoustic wave transducer. The acoustic reflectors are composed of acoustic reflection elements spaced approximately one wavelength apart, and provide enhanced acoustic acoustic reflections together with relaxed fabrication constraints.

Abstract: A surface acoustic wave resonator having an interdigital transducer on a piezoelectric substrate. Grating reflectors, which have electrode strips of the same width and the same pitch as those of electrodes of the interdigital transducer and of a number smaller than 1/5 that of said electrodes of said interdigital transducer, are disposed at the intervals equal to said pitch at both sides of said interdigital transducer on a surface wave propagation path. The electrode portion of the interdigital transducer is weighted so that the aperture of the interdigital transducer is maximum at the center of the interdigital transducer and uniformly decreases toward its both sides along respective sides of a rhombus with its vertices at the centers of the outermost electrode strips of the grating reflectors.

Abstract: A surface acoustic wave device includes a substrate having a surface which supports surface acoustic wave propagation and having a pair of interdigitated transducers disposed thereon. Each of the pair of interdigitated transducers has a set conductive members. To improve the ratio of devices having acceptable long-term frequency stability characteristics to those without such acceptable characteristics, the conductive members of the pair of interdigitated transducers have a larger than conventional thickness.

Abstract: A narrow band interference signal removing device uses first diode arrays and second diode arrays both provided in propagation paths of surface acoustic waves in order for the first diode arrays to detect the signal magnitude of a surface acoustic wave propagating in an opposite direction to obtain information on the spectrum magnitude of an input signal and responsively control a bias to the second diode arrays.

Abstract: An SAW convolver is disclosed, in which a pair of input transducer means disposed at the left and right end portions on a piezoelectric substrate having a velocity dispersion consists of a plurality of pairs of input transducers and the distance between different pairs of input transducers differs from each other so as to compensate the velocity dispersion.

Abstract: A demodulator for a spread spectrum communication system, including a piezoelectric substrate for causing elastic surface waves, an input electrode provided on the surface of the piezoelectric substrate, an intermediate electrode provided on the piezoelectric substrate surface a predetermined distance away from the input electrode, so as to form a matched filter together with the input electrode, and an output electrode provided on the piezoelectric substrate surface at a predetermined distance away from the intermediate electrode, so as to form a delay path together with the intermediate electrode.

Abstract: A surface acoustic wave device comprises a substrate, a plurality of input transducers formed on the substrate for generating first and second surface acoustic waves propagating in opposite directions to each other, and a plurality of waveguides arranged in a direction orthogonal to the propagating direction of the first and second surface acoustic waves on a region where the first and second surface acoustic waves overlap. Each waveguide producing a third surface acoustic wave propagating in a direction where the waveguides are arranged, with the interaction between the first and second surface acoustic waves, and on at least two of the waveguides, third surface acoustic waves reflected at respective side edges cancel each other, and an output transducer converts the third surface acoustic waves propagating from the waveguides into an electrical signal.

Abstract: A surface wave device utilizing a surface wave of an SH type whose displacement is mainly displacement in the direction perpendicular to the direction of the surface wave propagation, the above piezoelectric substrate being made of a piezoelectric material whose ratio of the elastic stiffness constant C.sub.33.sup.D to the elastic stiffness constant C.sub.44.sup.E is more than 4.

Abstract: A surface acoustic wave (SAW) chirp signal processor having a piezoelectric substrate, an array of input transducers and an array of output transducers. In its chirp compression mode, the device has chirp signals applied in parallel to its input transducers and produces compressed output pulses at its output transducers, corresponding to selected chirp rates. The input transducers are successively offset with respect to a focal point on the array of output transducers, by distances that successively and linearly increase or decrease from transducer to transducer, consistent with the increase or decrease in the wavelength of the chirp signals. The device may also be used in a pulse expansion mode, by inputting a broadband pulse into a selected one of the output transducers. The input transducers then produce a chirp signal having a rate corresponding the selected to output transducer.

Abstract: A SAW device comprises a substrate, input and output interdigital electrodes provided on the substrate alternately to form a row of electrodes, and a pair of open strip reflectors disposed at both ends of the row, the input interdigital electrodes having a first pair number representing the number of pairs of opposing finger electrodes forming the input electrode, the output interdigital electrodes having a second pair number representing the number of pairs of opposing finger electrodes forming the output electrode, wherein the first pair number and second pair number are set different in the adjacent input and output electrodes with a predetermined ratio therebetween, the first pair number is changed in each input electrodes in the row, and the second pair number is changed in each output electrodes in the row.

Abstract: A surface elastic wave filter includes a plurality of input interdigital transducers for receiving a high-frequency input signal, and a plurality of output inter-digital transducers for producing an output signal derived from the input signal and having predetermined frequency characteristics. Each of the input and output interdigital transducers having a pair of confronting connectors for receiving the input signal and extracting the output signal, respectively, and a pair of groups of interdigitating electrode fingers extending from the connectors. The input and/or output interdigital transducers include finger-withdrawn interdigital transducers with electrode fingers selectively withdrawn in different positions. With such withdrawal weighting, the interdigital transducers have different sidelobe characteristics, i.e., frequency blocking characteristics, so that the surface elastic wave filter operates with a greater sidelobe suppression.

Abstract: A bulk acoustic signal processor for processing GHz range R.F. signals employs a transmitter array comprised of an apodized set of subdivided interdigital electrodes mounted on a bulk wave launching crystal, the apodization being defined by the shape of an aperture in a layer of dielectric material on the crystal, over which the electrodes extend into contact with the surface of crystal for stressing the crystal and launching an acoustic wave into the bulk on which the crystal is mounted. Because a respective subdivided set of interdigital electrode elements has an impedance on the order of 0.5 to 6 ohms, each set is driven by a dedicated, impedance-transforming GaAs FET source-follower amplifier. When driven by an R.F.

Abstract: An acoustic transducer for an acoustic wave device which includes an acoustic wave propagating substrate, the transducer adapted to couple to an electrical load and/or source. The transducer includes at least a pair of comb electrodes formed on the substrate. It includes apparatus for applying an electrical load and/or source across the pair of comb electrodes. The first of the combs has a plurality of electrode fingers. The second comb has at least one electrode finger. The widths of the electrode fingers are the same. Gaps of at least two different widths are disposed between the electrodes.

Abstract: Interdigital transducers (3, 4) and reflectors (5, 6) are formed on a piezoelectric substrate (2) by an aluminum film. The aluminum film is crystallographically oriented in a constant direction, whereby stressmigration of the aluminum film is suppressed.

Abstract: An ACT (acoustic charge transport) filter comprises a plurality of SAW (surface acoustic wave) transducers and an interleaved filter bank coupled on either transversal side of the SAW transducer. Each interleaved filter bank comprises two filters, and the electrodes of the two filters are interleaved. Isolation between the interleaved electrodes is supplied by a meadering ground. The electrodes are apodized to facilitate weighted sampling of the delayed signal. Multiple frequency characteristics may be extracted from a single ACT filter by cascading the SAW transducer/interleaved filter bank combinations. Weighted sampling of the delayed signal may also be accomplished through weighted withdrawal of the ACT filter.

Abstract: Interdigital transducers and reflectors are formed on a piezoelectric substrate from an aluminum film. The aluminum film is formed by electron beam deposition at a film forming rate which is controlled to be at least 20 .ANG. per second. The aluminum film formed in this way is crystallographically oriented in a constant direction, whereby stressmigration of the aluminum film is suppressed.

Abstract: Biasing electrodes on a piezoelectric acoustic vibrator alter the sensitivity of the acoustic vibrator and can be used to compensate for external stresses applied to the acoustic vibrator. The biasing electrodes and the circuitry providing electric signals to them are separate from the RF circuitry feeding the RF signal electrodes of the acoustic vibrator. Biasing electrodes can be used on bulk acoustic wave devices or surface acoustic wave devices. The biasing electrodes can be energized by a static D.C. voltage source, or can be used in a dynamic biasing arrangement to provide instantaneous compensation for changing environmental conditions.

Abstract: A SAW device having a piezoelectric substrate and interleaved metal electrodes formed on the substrate, in which the formation of the electrodes on the substrate is carried out by sputtering. Further, the metal electrodes may contain an additive of Cu, Ti, Zn, Mg, Fe, Ni, Cr, Ga, Ge, Sn, Pd or Ta. The resulting SAW device is capable of dealing with high frequency electric signals of a larger amplitude, or higher power electric signals, as compared with the conventional SAW device.

Abstract: A surface acoustic electric wave device of the type comprising, over a large face of a planar piezo-electric substrate, a first row of parallel conductive fingers having an individual geometry chosen and distributed according to a chosen distribution arrangement along this row, a second row of parallel conductive fingers having an individual geometry chosen and distributed according to a chosen distribution arrangement along this row, the second row being interspaced from the first so as to allow a propagation of surface acoustic waves between the fingers of the first row and those of the second, which imparts to the device spectral and/or temporal characteristics defined by the acoustic propagation and the frequency selectivity due to the geometry of the fingers.

Abstract: A dispersive surface acoustic wave delay line device consists of a plurality of delay line elements which are disposed parallely so that a propagating path of a delay line element is not co-owned by the other delay line elements, in order to reduce secondary effects caused by electrode fingers.

Abstract: A plurality of interdigital transducers (IDTs) of a surface acoustic wave bandpass filter, each of which has a plurality of electrode fingers arranged in a direction perpendicular to a propagating direction of surface acoustic wave, are connected alternatively to an input terminal and an output terminal of said filter. The IDTs are different in number of electrode fingers and in average value of inter-finger distance from each other and distance between adjacent IDTs are different. At least one of the outermost IDTs has a minimum number of electrode fingers and a maximum average value of inter-finger distance, compared with those of other IDTs.

Abstract: An acoustic charge transport device having a number of signal tap electrodes has revealed unexpected insensitivity to electrode spacing and unexpected sensitivity to electrode width. Spacing of one-half SAW wavelength between consecutive electrodes and an electrode width of .lambda./20 are preferred for low frequency response.

Abstract: A surface wave filter has two tracks formed by interdigital transducers and coupling transducers on a substrate, wherein center-to-center path distances are defined between the transducers of a track. The relative center-to-center distances between the transducers comply with a particular relationship that depends on wavelength of the surface wave in the substrate. Correction factors are also applied to the relative relationships, which depend on whether the transducers defining each center-to-center distance are of the same type (symmetric or asymmetric) or whether one transducer is on one type and the other is of the other type within a track.

Abstract: This invention features a method for encoding surface acousting wave (SAW) delay lines. The method uses a split-electrode transducer as a programmable reflector. When shorted out, it does not reflect surface waves. When open-circuited, it partially reflects incident surface waves. As manufactured by conventional photolithographic methods, each of several such transducers is shorted out by a fusible link. In the as-manufactured state, the array of shorted transducers produces no reflection of surface waves. If a fusible link is destroyed by passage of electric current or other means, the corresponding transducer becomes a partial reflector. The status of these switchable reflectors may be read by exciting a separate launch transducer with a burst of electromagnetic energy containing substantial energy at the basis operating frequency of the SAW transducers or at suitable harmonics.