Abstract: In a SAW filter, first and second geometrically parallel two-port SAW resonators, each operable in triple longitudinal modes having first through third resonance peaks in a descending frequency order, are electrically parallel connected on a piezoelectric substrate to have lower and higher frequency passbands with the first and the second resonance peaks of the lower frequency passband brought into substantial coincidence in frequency with the second and the third resonance peaks of the higher frequency passband.

Abstract: The invention concerns unidirectional ground-wave transducers using an alternating series of emitter cells (E) and reflector cells (R).The invention consists in using, in the emitter cells (E), fingers having a width of .lambda./3 spaced apart by a distance of 2 .lambda./3; and, in the reflector cells (R), fingers having a width of .lambda./4 spaced apart by a distance of .lambda./2.Using identical engraving precision, the invention makes it possible to increase by 50% the frequency at which the unidirectional transducer thus produced can be used.

Abstract: An acoustic wave device in which the propagation path of the surface acoustic wave device is folded to increase the wave propagation path length in order to make better use of the total chip space.

Abstract: A correlator includes a reference signal generating device for generating a reference signal with period T, n-convolvers each having an action time of T/n where n is an integer of at least 2, into each of which an information signal and a reference signal are input and each of which outputs a convolution signal of the information signal and the reference signal, a delay device for delaying an information signal input into a k-th convolver among the n convolvers for a time of (k-1)T/n where k=1, 2, . . . , n and for delaying a reference signal input into the k-th convolver for a time of (n-k)T/n, and an adder for adding convolution signals respectively output from the n convolvers. A receiver includes such a correlator for outputting a correlation signal of a received information signal and a reference signal, and a decoding circuit for decoding data from the correlation signal output from the correlator.

Abstract: The invention relates to a SAW filter comprising a first and second pair of substantially equivalent SAW transducers electrically coupled to form a bridge circuit. Each of the transducers of the first pair of transducers have a center frequency which is slightly different to the center frequency of each of the transducers of the second pair of transducers. The product of the static capacitance of the first pair is the same as the product of the static capacitance of the second pair. In use, signals input to the filter and having a frequency within the passband of the filter are coupled to the output of the bridge circuit via one or other or both arms of the bridge, as in normal bridge circuit operation. However, out of band signals are blocked since all the transducers are equivalent capacitors having the same capacitance (i.e., static capacitance). Thus, transmission of out of band signals through the filter is inhibited by the balanced nature of the bridge.

Abstract: In a surface acoustic wave (SAW) filter, on a 36.degree. Y-cut X-propagation lithium tantalate substrate, series branch SAW resonators, which are connected in series between an input terminal and an output terminal, and parallel branch SAW resonators, which are connected between respective pairs of the series branch resonators by wirings and which are grounded, are provided. Two series branch resonators and one parallel branch resonator are connected in a T shape, so as to form a fundamental unit. In the SAW filter, three fundamental units are serially connected. An interdigital transducer (IDT) included in each resonator is made of a metal film containing aluminum as the main component. The thickness of the metal film is in the range of 8% to 10% of the electrode pitch of the IDT of the parallel branch resonator.

Abstract: To obtain a surface acoustic wave device which can be produced with ease at a low cost and can be reduced in size without causing deterioration of characteristics, a surface acoustic wave device having input and output transducers arranged alternately on the surface of a substrate for propagating a surface acoustic wave includes metal patterns provided outside the transducers along the extension line of the propagation path of the surface acoustic wave and having at least one surface inclined at an angle .theta.(5.degree.<.theta.<85.degree. or -85.degree.<.theta.<-5.degree.) with respect to the propagation direction of the surface acoustic wave.

Abstract: A three electrode type SAW longitudinal coupling filter includes a piezoelectric substrate having an electromechanical coupling factor (K.sup.2) higher than 10% and, three sets in total of input electrodes and output electrodes. Each of the electrodes includes a plurality of a electrode fingers of comb shape and are formed on the piezoelectric substrate. Reflectors are disposed at opposite sides of the input electrodes and output electrodes. The number of pairs of electrode fingers of the input electrodes is differentiated from the number of pairs of electrode fingers of the output electrodes. By the above arrangement, a large pass-band width can be obtained with small ripples and with an increase of the attenuation amount outside the band region.

Abstract: A chemical sensor includes a piezoelectric support (1) capable of supporting a shear horizontal wave provided on its surface with an electrode (2,3). The sensor is characterized in that the surface of the piezoelectric support (1) including the region bearing the electrode (2,3) is covered by a layer of dielectric material (9) of thickness 0.5 to 20 microns. The piezoelectric support (1) is preferably a single crystal. The dielectric layer (1) may be of, for example, silicon dioxide or a suitable polymer, and preferably has a thickness of between 0.5 and 5 .mu.m.

Abstract: A surface acoustic wave device includes a piezoelectric substrate, a wave guide path provided on the piezoelectric substrate and an interdigital transducer for exciting a surface acoustic wave. The interdigital transducer is provided with plural portions of mutually different pitches of the electrode finger, respectively corresponding to different frequencies. The portions are parallelly arranged along a direction perpendicular to the propagation direction of the surface acoustic wave. The surface acoustic wave generated by the interdigital transducer is entered in concentrated manner into the wave guide path.

Abstract: A real time non-volatile residue (NVR) monitor, which utilizes surface acoustic wave (SAW) resonators to detect molecular contamination in a given environment. The SAW resonators operate at a resonant frequency of approximately 200 MHz-2,000 MHz which enables the NVR monitor to detect molecular contamination on the order of 10.sup.-11 g-cm.sup.-2 to 10.sup.-13 g-cm.sup.-2. The NVR monitor utilizes active temperature control of (SAW) resonators to achieve a stable resonant frequency. The temperature control system of the NVR monitor is able to directly heat and cool the SAW resonators utilizing a thermoelectric element to maintain the resonators at a preset temperature independent of the environmental conditions. In order to enable the direct heating and cooling of the SAW resonators, the SAW resonators are operatively mounted to a heat sink.

Abstract: A Passive Surface Acoustic Wave Identification Tag ("SAW-ID tag") device utilizes pulse compression techniques and a large number of coding possibilities for identifying articles at enhanced ranges. The SAW-ID tag device provides a piezoelectric substrate having bus bars, spaced electrode taps between the bus bars and a built-in antenna, with an input chirped SAW transducer having a dispersive, complementary matched filter response to an input expanded chirp signal from an expanded linear FM chirp waveform actively generated by a nearby chirp transmitter. The input expanded chirp signal is fed into the input chirped SAW transducer through the built-in antenna, to compresses the input expanded chirp signal into a narrow, compressed pulse signal propagating toward the electrodes taps. The spacing of the electrode taps establishes the desired unique time-ordered coding.

Abstract: An elastic convolver 11 constructed by forming a set of input idts 13 spaced apart from each other by a predetermined distance on an LiNbO.sub.3 piezoelectric substrate, forming a waveguide path 14 in the center of an area between the IDTs 13, respectively forming multistrip couplers 15 between the waveguide path 14 and tile IDTs 13, and forming ZnO piezoelectric thin films 16 so as to cover at least the IDTs 13 and so as not to cover the guide path 14.

Abstract: A piezoelectric crystal element for surface acoustic wave applications with a quartz substrate with at least one substantially planar quartz surface, the planar quartz surface having an epitaxially grown layer of a quartz-isomorphous crystal with the total molecular formula ABO.sub.4, A standing for Al or Ga, and B for P or As, and the quartz surface and the epitaxial layer having approximately the same crystallographic orientation.

Abstract: An acoustic wave filter with reduced bulk-wave scattering loss has a center frequency and an associated acoustic wavelength. The filter includes a substrate and a first reflector having a first group of periodically disposed reflective elements. The filter includes a first transducer on a first side of the first reflector. The filter also includes a first gap having a first width, located between the first reflector and the first transducer. The first width exceeds one-fourth of the acoustic wavelength. The filter includes a second reflector and a second gap disposed between the first transducer and the second reflector. The second gap has a second breadth exceeding one-fourth of the acoustic wavelength. A first waveguiding element is positioned within the first gap and having a first breadth. The first width exceeds the first breadth.

Abstract: A novel surface acoustic wave device that includes a multiple track transducer having a first portion for generating a transverse symmetrical mode acoustic wave and a second portion for receiving only a transverse nonsymmetrical surface acoustic wave such that substantially no direct coupling occurs between the first and second portions of the multiple track transducer and where reflector gratings are mode changing gratings that reflect the transverse symmetrical wave as a transverse nonsymmetrical wave that is received by the second portion of the multiple track transducer thereby substantially reducing undesired in-band surface acoustic wave transducer responses as well as spurious bulk responses and allowing a narrow passband to be obtained with a short structure when compared with the prior art structures.

Abstract: Electrical components, such as filters, oscillators, resonators and delay lines are manufactured from a piezo ceramic base which includes a depolarized zone. The sound velocity is set by topically heating a portion of the base to form the depolarized zone between a pair of transducers.

Abstract: Surface-wave arrangement (1) having at least one surface structure (21, 22), by means of which those components of surface waves (19) which are produced in the arrangement are rendered ineffective with respect to interference which would otherwise occur, for which a sump is provided in a known manner at the end of the substrate.

Abstract: An improved surface acoustic wave grating structure that utilizes four electrodes per 3.lambda./2 or 5.lambda./2 transduction length of a reflector grating structure that produces a desired net internal distributed reflectivity in both magnitude and phase.

Abstract: To obtain a surface acoustic wave device which can be produced with ease at a low cost and can be reduced in size without causing deterioration of characteristics, a surface acoustic wave device having input and output transducers arranged alternately on the surface of a substrate for propagating a surface acoustic wave includes metal patterns provided outside the transducers along the extension line of the propagation path of the surface acoustic wave and having at least one surface inclined at an angle .theta. (5.degree.<.theta.<85.degree. or -85.degree.<.theta.<-5.degree.) with respect to the propagation direction of the surface acoustic wave.

Abstract: A surface wave reflection filter includes an input transducer, an output transducer, and a reflector in a first propagation track. To compensate for undesired surface waves proceeding directly between the input and output transducers, as opposed to the desired surface waves which are reflected before reaching the output transducer, a second propagation track is provided. The second track includes a input transducer and an output transducer, and is either connected in phase opposition to compensate for the undesired signal, or is constructed to generate a signal in phase opposition. A sump may be provided in the second track, a second reflector may be provided in the first track or in the second track, and the two tracks may be on separate or the same substrates.

Abstract: A surface acoustic wave device includes a piezoelectric substrate, an input electrode formed on the substrate and an output electrode formed on the substrate. A surface acoustic wave is generated from the input electrode to propagate in a predetermined direction in accordance with an input signal. In the output electrode, a plurality of taps are arranged in a propagation direction of the surface acoustic wave on the substrate. The surface acoustic wave is converted into an electrical signal by the output electrode. The taps of the output electrode are weighted so that signals output from the taps have substantially equal magnitudes.

Abstract: A surface acoustic wave device for generating an output signal with only a symmetric or only an asymmetric vibration acoustic wave mode in a piezoelectric substrate. The device has first and second transversely spaced transducers and the device is driven from both the first and second transducers. A third transducer is between and acoustically coupled to the first two transducers. The electrodes of all three transducers are arranged with respect to each other so as to cause only a symmetrical acoustic vibration mode or only an asymmetrical acoustic vibration mode in the piezoelectric substrate.

Abstract: An acoustic or ultrasonic device includes two ultrasonic energy transmission paths having substantially identical transmission characteristics for a neutral condition of the device. One or both of the transmission paths include path altering structure(s) or coating(s) for changing the transmission characteristics of one or both of the paths in response to a physical phenomenon to be sensed or monitored. The paths have input transducers coupled thereto for transmitting ultrasonic energy into the paths. The input transducers are driven by a single oscillator such that the ultrasonic energy waves generated in the two paths are substantially identical to one another. A drive adjusting circuit compensates for any differences between the two paths and/or the ultrasonic waves in the two paths. An output transducer is coupled to the two paths for receiving ultrasonic waves from the paths and generating an output signal which is the result of combining the acoustic or ultrasonic waves from the two paths.

Abstract: A surface acoustic wave element is provided with a piezoelectic substrate, a first input transducer, a second input transducer and an output device such as output electrode. The piezoelectric substrate has a first and a second surfaces which are mutually faced. The first input transducer is formed on the first surface of the substrate to generate a first surface acoustic wave which propagates in a predetermined direction. The second transducer is formed on the first surface of the substrate to generate a second surface acoustic wave which propagates in a direction opposite to the predetermined direction. The output device is formed on the first surface of the substrate to extract a signal produced by an interaction of the first and second surface acoustic waves. At least part of the second surface of the substrate is caused to be inclined in a direction perpendicular to the predetermined direction with respect to the first surface.

Abstract: A surface-wave filter in which the acoustic wavepath is reflected in order to reduce the substrate size necessary. The reflections are chosen so that interference due to temperature effects is excluded. The use of filters of this kind as partial filters in a combined filter enables cross-talk to be further reduced.

Abstract: A double mode surface wave resonator comprises two IDTs (inter-digital transducers), arranged side by side between reflection gratings, on a surface of a piezoelectric substrate to provide for coupling of surface waves therebetween, each IDT having interleaved electrodes extending from a common rail between the two IDTs and from a respective outer rail of the IDT. One or each of the IDTs and its outer rail is divided into two halves for providing a differential signal connection to the resonator. The electrodes of the IDTs can be arranged in spatial synchronism with adjacent fingers of the reflection gratings to reduce spurious longitudinal modes.

Abstract: A SAW resonator/filter structure (300) includes a transducer portion. The transducer portion includes a plurality of acoustically coupled sub-transducer portions (310 and 312) comprising conductive patterns having interdigitated open-ended fingers. The sub-transducer portions (310 and 312) are electrically coupled to each other in series in order to increase the port impedance of the SAW filter structure (300) while providing the widest bandwidth.

Abstract: A SAW filter structure (300) includes two SAW resonators being symmetrically positioned along parallel tracks. The resonators include centrally positioned resonator gaps (368, 378) which are opposingly positioned. A multistrip coupler (330) for acoustically coupling the resonators extends between the resonator gaps and includes a plurality of equally spaced strips (8812) which are spaced to permit omni-directional projection of acoustic waves from the opposing sides of the multi strip coupler.

Abstract: An electronic article surveillance system including a bulk acoustic wave transponder 10 coupled to an antenna 12, an interrogator 14, directional antenna 16 and an output connector 18. The transponder comprises a silicon or glass substrate 20, bus electrodes 22, 24, a launching IDT T0 and a series of "connected" and "unconnected" IDTs T1-T4. The connected/unconnected state of the respective IDTs T1-T4 may be detected and employed to generate an identification code comprising a series of binary digits. A thin copolymer piezoelectric film 26 covers the substrate 20 and electrodes T0-T4.

Abstract: In a surface acoustic wave device, there are arranged a piezoelectric substrate, an input electrode and an output electrode. The input electrode is formed on the substrate, and generates a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal. The output electrode is also formed on the substrate, and converts the surface acoustic wave to an electric signal. One of the input and output electrodes includes a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave. The other one of the input and output electrodes may comprise a pair of taps arranged at a predetermined distance in the propagation direction. The electrode including a plurality of taps or the electrode including a pair of taps satifies a predetermined relation established among a length between the taps, a transmission speed of the input signal, a propagation velocity of the surface acoustic wave and so forth.

Abstract: An in-line surface-wave reflector filter having an input/output transducer system (2, 12/4) in which direct acoustic signal transmission between input and output is eliminated.

Abstract: A two track surface wave arrangement has improved selection property resulting from crosstalk signals of parasitic transmission paths within the arrangement being suppressed. What can be achieved with a displacement of the surface wave arrangement of one track relative to that of the other track by a dimension of nearly half a wavelength is that crosstalk signals mutually cancel on the basis of interference without affecting the useful signal.

Abstract: A SAW device such as a resonator includes a surface supporting surface wave propagation and a pair of aluminum transducer elements each coupled to said surface wave propagation surface. Each aluminum transducer element is doped with a predetermined amount of silicon. Frequency shifts which result from exposing the SAW device to high temperature cycles as often encountered when packaging the device are reduced, since the silicon present as a dopant in the aluminum will provide an effect on frequency which can be taken into consideration during design and fabrication. These frequency effects will dominate any frequency effects which may result from silicon migration from the substrate to the transducers as a result of the thermal cycling encountered during sealing of the SAW device.

Abstract: A surface acoustic wave convolver includes first and second interdigital electrodes for exciting surface acoustic waves and an output electrode for detecting the surface acoustic waves to extract a convolution output as an electrical signal, the first and second interdigital electrodes and the output electrode being formed on a piezoelectric or electrostrictive substrate.

Abstract: A filter device comprises an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 and having a first filter and a second filter disposed on the acoustic wave propagating substrate. The first filter comprises a first electro-acoustic transducer and a first acousto-electric transducer, both disposed on the acoustic wave propagating substrate. The first acousto-electric transducer comprises N.sub.1 many electrode pairs, wherein N.sub.1 .gtoreq.C/k.sup.2. C is a constant having a value in the range from 1 to 2. The first acousto-electric transducer is acoustically coupled to the first electro-acoustic transducer. The second filter comprises a second electro-acoustic transducer and a second acousto-electric transducer, both disposed on the acoustic wave propagating substrate. The second electro-acoustic transducer is electrically coupled to the first acousto-electric transducer. The second electro-acoustic transducer comprises N.sub.2 many electrode pairs, wherein N.sub.2 <C/k.

Abstract: A sensor for chemical vapor detection using a surface acoustic wave (SAW) ray that provides a means for simultaneously detecting several chemical agents. The sensor has a piezoelectric substrate and a bidirectional surface acoustic wave transducer on the substrate. Also on the substrate are several pairs of identical acoustic sensing and reference channels each on opposite sides of the transducer in a mirror image fashion. Each channel pair has a thin film capable of absorbing a chemical vapor to be monitored and a metallic surface acoustic wave grating reflector capable of receiving and reflecting surface acoustic waves through the thin film and back to the transducer. An acoustic absorber separates each channel. The reference channels are protected from ambient conditions while the sensing channels are exposed to such conditions. An RF signal is applied to the transducer causing the propagation of an acoustic signal into each of the sensing channels and reference channels.

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: 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 sensor suitable for use as a viscosity sensor, a chemically selective sensor, or a chemically specific sensor. The sensor is a surface transverse wave (STW) or Love Wave device that, for solute concentration measurements, includes a chemically reactive layer selected to react with the solute to be measured. The surface trapping structure in this device can include dielectric material either as a protective coating or as the core material of the surface trapping structure. The substrate material and cut are selected so that only shear horizontal acoustic waves are produced. Nonpiezoelectric portions of this device can be utilized in the region in which chemicals react the sensor and/or in the region in which energy is converted between electrical and acoustical forms.

Abstract: A GaAs piezoelectric semiconductor thin film in the form of an epitaxial film is provided on a Si substrate 1, and an input transducer 3 and an output transducer 4 for input and output of a surface acoustic wave are provided on the film. A surface acoustic wave element, thus arranged, has a sound characteristic superior to that of a single crystalline GaAs substrate and permits the use of an electromechanical coupling coefficient larger than that of the single crystalline GaAs. Thus the element copes with a much higher sound velocity of SAWs.

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: A reflector arrangement for an acoustic wave device comprises an acoustic wave propagating substrate, reflection elements having at least two different widths separated by at least one gap breadth disposed on the acoustic wave propagating substrate. The at least two different widths enhance reflected waves produced by the propagating acoustic wave in such a fashion to as to achieve a total acoustic reflectivity which is independent of variations in width of the reflection elements.

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: In an SAW convolver device constructed by sealing an SAW convolver element having a piezoelectric film/insulator/semiconductor structure by means of a cover of a package, according to the present invention, an insulating base plate is disposed on a part of a metallic base plate of the package, on which insulating base plate there is disposed a resistor or a coil, and the gate electrode of the convolver is grounded in a DC-like manner through the resistor or coil.Owing to the construction described above, it is possible to prevent that a voltage due to electrostatic charge, an accidental voltage due to erroneous handling, etc. are applied to the gate electrode of a zero bias type SAW convolver. As the result, it is possible to stabilize characteristics of the zero bias type SAW convolver for a long period of time and to improve the reliability thereof.

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.