Showing papers on "Surface acoustic wave published in 2002"
TL;DR: In this paper, the authors present a survey of microwave applications of acoustic waves, including thin-film resonators and filters, transversal filters, and filters for correlative analog signal processing.
Abstract: This paper surveys applications of acoustic waves in microwave devices. After a general and historical introduction to bulk acoustic waves (BAWs), surface acoustic waves (SAWs), practical wave types, and acoustoelectric transducers, a review is given of technologically important materials for microwave acoustic applications. Following this, we discuss BAW and SAW microwave devices and their technologies. Specifically reviewed are thin-film resonators and filters, transversal filters, and filters for correlative analog signal processing. Finally, an overview of the most important microwave applications is given, along with manufacturing and packaging issues.
196 citations
08 Oct 2002
TL;DR: Coupled Resonator Filters (CRF) as mentioned in this paper are a new form of bulk acoustic wave device that involves the vertical stacking of resonators, which can be thought of as a variation on the better known Stacked Crystal Filter (SCF).
Abstract: Coupled Resonator Filters (CRF) are a new form of bulk acoustic wave device that involves the vertical stacking of resonators. In that regard, the CRF can be thought of as a variation on the better known Stacked Crystal Filter (SCF). This paper will review the SCF and expand on the basic concepts of the CRF. Experimental results will be shown for SCFs operating to 12 GHz and CRFs near 3 GHz. Manufacturing issues associated with both filter types will be reviewed with greater emphasis on the CRF.
147 citations
TL;DR: In this article, a hydrogen sensor based on a bilayer structure in a surface acoustic wave (SAW) dual delay line system is presented, where the sensor material consists of two layers performed in two different vapour deposition processes.
Abstract: Presented here are the results concerning a hydrogen sensor based on a bilayer structure in a surface acoustic wave (SAW) dual delay line system. The sensor material consists of two layers performed in two different vapour deposition processes. The first one is a 720 nm copper phthalocyanine (CuPc) layer, the second is a 20 nm thin palladium (Pd) film. This structure was formed in one of the dual delay line systems on a LiNbO3 Y-cut Z-propagation substrate, while the other serves as a reference, permitting easy detection of the arising differential frequency Δf. This frequency, depending on the operating frequency modes, is in the range of 200–400 kHz, whereas the oscillator frequencies are in the range of 43.6 MHz. The wavelength is 80 μm. In such a bilayer structure we can detect hydrogen in a medium concentration range (from 0.5 to 3% in nitrogen), even at room temperature. The sensor is highly sensitive, very stable and is entirely reversible. The response and recovery times defined as 90% of the saturation level are quite good (from 100 s for 0.5% to 1000 s for 1.5%), which is very important from a practical point of view. The sensitivity depends on temperature, and decreases with the increase of the interaction temperature. In addition, the phase transition of the palladium hydride at 30 and 43 °C is distinct and repeatably visible as an “interaction jump”, which is something of a disadvantage in respect of the sensor. This undesirable phase transition shifts in the direction of higher hydrogen concentrations at higher temperatures, and consequently can be avoided; for instance, at 61 °C for the investigated concentration range (0.5–3% of hydrogen in nitrogen).
123 citations
Patent•
22 Apr 2002TL;DR: In this paper, high quality single-crystal piezoelectric material is transferred to an appropriate substrate using hydrogen ion implant layer splitting and bonding and the oxide is then planarized using chemical mechanical polishing.
Abstract: Thin layers of high quality single-crystal piezoelectric material, high temperature sintered piezoelectric material, or high quality thin film grown material are transferred to an appropriate substrate using hydrogen ion implant layer splitting and bonding. The substrate to which the thin piezoelectric material layer is transferred may contain CMOS or GaAs circuitry. When the substrate contains CMOS or GaAs circuitry, the circuitry on the surface of the GaAs or CMOS substrate may be covered with an oxide. The oxide is then planarized using chemical mechanical polishing, and the thin film resonator material is transferred to the GaAs or CMOS circuit using wafer bonding and hydrogen ion layer splitting.
115 citations
TL;DR: In this paper, high quality surface acoustic wave (SAW) filters based on aluminum nitride (AlN)/diamond layered structures were prepared using the nucleation side of polycrystalline chemical vapor deposition (CVD) diamond, removed from a silicon substrate by wet etching.
Abstract: High-quality surface acoustic wave (SAW) filters based on aluminum nitride (AlN)/diamond layered structures were prepared using the nucleation side of polycrystalline chemical vapor deposition (CVD) diamond, removed from a silicon substrate by wet etching. Highly oriented AlN thin films with optimized piezoelectric properties and with various thicknesses were sputtered onto the nucleation side of freestanding diamond. The effect of AlN thickness on the SAW phase velocity, the coupling coefficient, and the device characteristics were investigated. Experimental results show that the Rayleigh wave and the higher modes are generated. These results agree well with calculated dispersion curves and demonstrate that a high electromechanical coupling coefficient together with a high phase velocity can be obtained by using the nucleation side of freestanding CVD diamond layer.
102 citations
08 Dec 2002
TL;DR: In this article, two different approaches for RF-MEMS filters are reviewed and compared: electric field driven MEMS-resonators and piezoelectric MEMS resonators.
Abstract: RF-MEMS filters will substitute conventional filters in mobile communication under certain technical and commercial conditions. Key performance parameters and requirements are discussed in detail. Two different approaches for RF-MEMS filters are reviewed and compared: Electric field driven MEMS-resonators and piezoelectric MEMS resonators. State-of-the-art RF-MEMS filters based on bulk-acoustic-wave (BAW) resonators are presented.
100 citations
TL;DR: In this article, a Love-mode surface acoustic wave (SAW) sensor with ZnO guiding layer and 90° rotated ST-cut quartz crystal substrate was presented, which offers distinct advantages over previously fabricated Lovemode structures.
Abstract: A novel Love-mode surface acoustic wave (SAW) sensor with ZnO guiding layer and 90° rotated ST-cut quartz crystal substrate will be presented. Analysis of this device with different thicknesses of ZnO films was undertaken. It will be shown that this novel structure offers distinct advantages over previously fabricated Love-mode structures. These advantages include significantly high sensitivity, small temperature coefficient of frequency and high electromechanical coupling coefficient.
92 citations
TL;DR: In this paper, an electrode effect on the quality factor and effective coupling coefficient empirically and theoretically was presented. And the authors found that the Q value of solidly mounted resonators (SMRs) is not determined by only the piezoelectric film quality, but by a weighted average of the electrode and piezoclectric films quality.
Abstract: This article presents an electrode effect on the quality factor and effective coupling coefficient empirically and theoretically. The possible quality factor detractors in film bulk acoustic wave resonator devices are the acoustic wave attenuation in the metal and piezoelectric films, the wave scattering loss due to the surface roughness, and the electrode electrical loss. Due to the small acoustic wave attenuation of the Mo electrode, the composite Mo–AlN–Mo resonator with the thick electrode provides higher Q values than the resonator with the good quality AlN film and the thin Mo electrode. In such Mo electroded resonators, the effective coupling coefficient is kept relatively high. It is found that the Q value of solidly mounted resonators (SMRs) is not determined by only the piezoelectric film quality, but by a weighted average of the electrode and piezoelectric film quality. Of Q value detractors, the scattering loss originating from surface roughness is thought to be very important factor in SMR quality value.
89 citations
TL;DR: A line-focus-beam ultrasonic material characterization (LFB-UMC) system has been developed to evaluate large diameter crystals and wafers currently used in electronic devices to address various problems arising in science and industry associated with the development of materials and device fabrication processes.
Abstract: A line-focus-beam ultrasonic material characterization (LFB-UMC) system has been developed to evaluate large diameter crystals and wafers currently used in electronic devices. The system enables highly accurate detection of slight changes in the physical and chemical properties in and among specimens. Material characterization proceeds by measuring the propagation characteristics, viz., phase velocity and attenuation, of Rayleigh-type leaky surface acoustic waves (LSAWs) excited on the water-loaded specimen surface. The measurement accuracy depends mainly upon the translation accuracy of the mechanical stages used in the system and the stability of the temperature environment. New precision mechanical translation stages have been developed, and the mechanical system, including the ultrasonic device and the specimen, has been installed in a temperature-controlled chamber to reduce thermal convection and conduction at the specimen. A method for precisely measuring temperature and longitudinal velocity in the water couplant has been developed, and a measurement procedure for precisely measuring the LSAW velocities has been completed, achieving greater relative accuracy to better than /spl plusmn/0.002% at any single chosen point and /spl plusmn/0.004% for two-dimensional measurements over a scanning area of a 200-mm diameter silicon single-crystal substrate. The system was developed to address various problems arising in science and industry associated with the development of materials and device fabrication processes.
84 citations
TL;DR: In this paper, a scattering matrix approach is proposed to avoid numerical instabilities arising with the classical transfer matrix method when analyzing the propagation of plane surface acoustic waves in piezoelectric multilayers.
Abstract: A scattering matrix approach is proposed to avoid numerical instabilities arising with the classical transfer matrix method when analyzing the propagation of plane surface acoustic waves in piezoelectric multilayers. The method is stable whatever the thickness of the layers, and the frequency or the slowness of the waves. The computation of the Green’s function and of the effective permittivity of the multilayer is outlined. In addition, the method can be easily extended to the case of interface acoustic waves.
83 citations
TL;DR: In this article, the capacitance and potential distribution of the interdigitated electrode system were derived based on the potential function of two conducting semi-infinite plates, which concur with the exact solution of the system.
Abstract: Interdigitated electrode systems are widely applied in sensors, photodiodes and surface acoustic wave (SAW) filters. The present paper adds to the body of knowledge on the capacitance and potential distribution of these systems. Approximate equations for the electrostatic potential and the capacitance of the interdigitated electrode system are derived based on the potential function of two conducting semi-infinite plates. The new equations concur with the exact solution of the interdigitated electrode system. Advantages of the new equations are the simple mathematical form and evaluation method.
Patent•
13 Sep 2002
TL;DR: In this paper, a surface acoustic wave device was proposed to reduce the size of the device itself by supporting one end part of an SAW chip at the side wall part standing on the base body part and supporting the other end part thereof on the body part.
Abstract: PROBLEM TO BE SOLVED: To provide a novel surface acoustic wave device in which the size of the device itself can be reduced by supporting one end part of an SAW chip at the side wall part standing on the base body part and supporting the other end part thereof on the base body part, thereby disposing a surface acoustic wave chip in an inclined manner SOLUTION: The surface acoustic wave device comprises a package, having a base substance part 2 and sidewall parts 3 and 4 standing on the peripheral end part thereof and provided with step parts 3a and 4a, a surface acoustic wave chip 1, having one end part 1a supported at the step part 3a and the other end part 1b supported on the base body part 2, so that the surface acoustic wave chip is disposed while being inclined, a cap 5 secured onto the sidewall part to cove the surface acoustic wave chip 1, a member 7 for bonding the other end of the surface acoustic wave chip 1 to the base body part, and a member 8 for electrically connecting the surface acoustic wave chip 1 and the package
Patent•
11 Apr 2002TL;DR: In this paper, a method for simply fabricating plural surface acoustic wave filter chip packages in large quantities comprising the steps of providing a wafer, on the surface of which plural SAWF chips are formed, and a package substrate, on which mounting portions corresponding to surface SAWFs are formed.
Abstract: Disclosed is a method for simply fabricating plural surface acoustic wave filter chip packages in large quantities comprising the steps of providing a wafer, on the surface of which plural surface acoustic wave filter chips are formed, and a package substrate, on the surface of which mounting portions corresponding to surface acoustic wave filter chips are formed; providing underfill on the package substrate; mounting the wafer on the package substrate; removing wafer portions between surface acoustic wave filter chips; forming metal shield layers on outer walls of separated surface acoustic wave filter chips; molding a resin on outer walls of surface acoustic wave filter chips coated with metal layers; and dividing the package substrate molded with resin into individual surface acoustic wave filter chip packages.
06 Aug 2002
TL;DR: In this article, the authors survey the operating principle of such sensors and their state-of-the-art performance and support illustrative examples such as temperature sensors and sensors for mechatronic applications.
Abstract: Surface acoustic wave (SAW) devices can be turned into novel identification and sensor elements (transponders) that do not need any power supply and may be interrogated wirelessly. Such a transponder picks up an electromagnetic request signal and stores it until all echoes caused by multipath propagation have died away. Then, a characteristic response signal is beamed back to the interrogator unit. In radio-link sensors, a physical or chemical quantity influences the propagation properties of the SAW and consequently changes the response pattern of the device. This contribution surveys the operating principle of such sensors and their state-of-the-art performance. The discussion is supported by illustrative examples such as temperature sensors and sensors for mechatronic applications.
TL;DR: Using the effective permittivity method, not only the null frequency bandwidth, but also the center frequency shift and insertion loss can be evaluated and an exact analysis for modeling the layered SAW device is proposed.
Abstract: In this paper, a formulation for calculating the effective permittivity of a piezoelectric layered SAW structure is given, and the exact frequency response of ZnO/diamond/Si-layered SAW is calculated. The effective permittivity and phase velocity dispersion of a ZnO/diamond/Si-layered half space are calculated and discussed. The frequency response of an unapodized SAW transducer is calculated, and the center frequency shift caused by the velocity dispersion is explained. In addition, the electromechanical coupling coefficients of the ZnO/diamond/Si-layered half space based on two different formulas are calculated and discussed. Finally, based on the results of the study, we propose an exact analysis for modeling the layered SAW device. The advantage of using the effective permittivity method is that, not only the null frequency bandwidth, but also the center frequency shift and insertion loss can be evaluated.
TL;DR: In this paper, the photoresponse of GaN-based surface acoustic wave (SAW) delay-line oscillator operating in the 200 MHz range is described, where the optical quenching of the photoconductivity in GaN was observed.
Abstract: We describe the photoresponse of GaN-based surface acoustic wave (SAW) delay-line oscillator operating in the 200 MHz range. The decrease in oscillator frequency under ultraviolet illumination of GaN transducer is caused by the SAW velocity decrease due to the acoustoelectronic interaction with photoconductivity electrons. The oscillator frequency shift reaches its maximum value at 365 nm and drops to zero above 400 nm with visible/ultraviolet rejection ratio more than 100. The optical quenching of the photoconductivity in GaN was observed. These results demonstrate the potential of the GaN-based SAW oscillators for applications as visible–blind remote UV sensors.
Patent•
20 Mar 2002TL;DR: In this article, a surface acoustic wave device with a high k2 and a frequency filter, oscillator, electronic circuit, and electronic device employing this surface wave device is provided, where a first oxide thin film comprising SrO or MgO and a second oxide thin layer comprising SrTiO3 are sequentially formed on top of a (110) Si substrate.
Abstract: Surface acoustic wave device having a high k2, and a frequency filter, oscillator, electronic circuit and electronic device employing this surface acoustic wave device is provided, wherein a first oxide thin film layer comprising SrO or MgO and a second oxide thin film layer comprising SrTiO3 are sequentially formed on top of a (110) Si substrate, or a first oxide thin film layer comprising CeO2, ZrO2 or yttrium-stabilized zirconia and a second oxide thin film layer comprising SrTiO3 are sequentially formed on top of a (100) Si substrate, a KNbO3 piezoelectric thin film being then formed on top of either of these second oxide thin film layers, and then, a protective film comprising oxide or nitride is formed on top of the KNbO3 piezoelectric thin film, finally, at least one electrode is formed on top of this protective film, to form a surface acoustic wave device, which surface acoustic wave device is employed to form a frequency filter, oscillator, electronic circuit, or electronic device.
TL;DR: An "optimized" position-independent reflection coefficient was defined to facilitate practical application and intersubject comparisons of inviscid acoustics in nonuniform waveguides.
Abstract: The sound power per unit cross-sectional area was determined in human ear canals using a new method based on measuring the pressure distribution (P) along the length of variable cross-section acoustic waveguides. The technique provides the pressure/power reflection coefficients (R/R) as well as the acoustic intensity of the nonplanar incident wave (I+, the acoustic input to the ear) and the nonplanar outgoing wave (I-, the acoustic output of the ear). Results were compared to the classical acoustic impedance (Z) and associated plane-wave power reflection coefficient (R(Z)). Performance of the method was investigated theoretically using horn equation simulations and evaluated experimentally using pressure data recorded in nonuniform waveguides. The method was applied in normal-hearing young adults to determine ear-canal position- and frequency-dependence of I(+/-), R, and R(Z) using random phase broadband stimuli (1-15 kHz; approximately 75 dB SPL). Reflection coefficient (R) measurements at two different locations within individual human ear canals exhibited a position dependence averaging deltaR approximately 0.1 (over 6 mm distance)--a difference consistent with predictions of inviscid acoustics in nonuniform waveguides. Since this position dependence was relatively small, an "optimized" position-independent reflection coefficient was defined to facilitate practical application and intersubject comparisons.
06 Jun 2002
TL;DR: In this article, the waveguide invariant is treated as a distribution and an algorithm for estimating this distribution for a general measurement geometry is developed for different classes of shallow water waveguides.
Abstract: The “invariant parameter” called “beta” is often useful for describing the acoustic interference pattern in a waveguide. For some shallow water waveguides, the measured acoustic intensity might contain contributions from several propagating acoustic modes. For each pair of these modes, a different value for the waveguide invariant might apply. If the acoustic intensity is measured over some distributed aperture and finite bandwidth, it may become difficult to assign a single value to beta. In the present work, the waveguide invariant is treated as a distribution. An algorithm for estimating this distribution for a general measurement geometry is developed. The algorithm is exercised for different classes of shallow water waveguides. When the propagation is dominated by modes interacting with the sea surface, the distribution can be sharply peaked. For cases where the sound speed profile creates a duct, the distribution is more diffuse. The effects of source/receiver depth, range, bandwidth and bottom attenuation are quantified.
TL;DR: In this article, a model for the mass sensitivity of Love wave and layer guided shear horizontal acoustic plate mode (SH-APM) sensors is developed by considering the propagation of shear horizontally polarized acoustic waves in a three layer system.
Abstract: A model for the mass sensitivity of Love wave and layer guided shear horizontal acoustic plate mode (SH–APM) sensors is developed by considering the propagation of shear horizontally polarized acoustic waves in a three layer system. A dispersion equation is derived for this three layer system and this is shown to contain the dispersion equation for the two layer system of the substrate and the guiding layer plus a term involving the third layer, which is regarded as a perturbing mass layer. This equation is valid for an arbitrary thickness perturbing mass layer. The perturbation, Δν, of the wave speed for the two-layer system by a thin third layer of density, ρp and thickness Δh is shown to be equal to the mass per unit area multiplied by a function dependent only on the properties of the substrate and the guiding layer, and the operating frequency of the sensor. The independence of the function from the properties of the third layer means that the mass sensitivity of the bare, two-layer, sensor operated about any thickness of the guiding layer can be deduced from the slope of the numerically or experimentally determined dispersion curve. Formulas are also derived for a Love wave on an infinite thickness substrate describing the change in mass sensitivity due to a change in frequency. The consequences of the various formulas for mass sensing applications are illustrated using numerical calculations with parameters describing a (rigid) poly(methylmethacrylate) wave-guiding layer on a finite thickness quartz substrate. These calculations demonstrate that a layer-guided SH–APM can have a mass sensitivity comparable to, or higher, than that of Love waves propagating on the same substrate. The increase in mass sensitivity of the layer guided SH–APMs over previously studied SH–APM sensors is of significance, particularly for liquid sensing applications. The relevance of the dispersion curve to experiments using higher frequencies or frequency hopping and to experiments using thick guiding layers is discussed.
TL;DR: In this paper, high surface-to-volume ratio coatings consisting of nano-scale polymer particles were applied to surface acoustic wave (SAW) transducers and compared with sensors developed from bulk films of the same polymers.
Abstract: High surface-to-volume ratio coatings consisting of nano-scale polymer particles were applied to surface acoustic wave (SAW) transducers. The resulting sensors were tested upon exposure to analyte vapors and were compared with sensors developed from bulk films of the same polymers. The relative importance of surface adsorption and bulk absorption was investigated and it is shown that high surface area coatings can be used to improve the sensitivity and response time particularly in the case of polymers exhibiting low vapor permeability. Furthermore, because the mean particle diameter is small compared to the spacing of the SAW interdigital electrodes, nano-scale particulate coatings appear acoustically uniform and are therefore, compatible with SAW technology. The high surface-to-volume ratio coatings were deposited using a spray-on technique known as rapid expansion of supercritical solutions (RESS) and both glassy and viscoelastic polymers were studied.
Patent•
16 Aug 2002
TL;DR: In this article, the stopping electrodes 2 and 3 which stop the surface acoustic wave from traveling straight by changing its direction are arranged between the element electrode and element end surface 1 of the SAW device to scatter the traveling direction of the acoustic wave.
Abstract: PURPOSE:To prevent a surface acoustic wave from being reflected by an element end surface to deteriorate characteristics by arranging stopping electrodes which stop a surface acoustic wave from traveling straight by changing its direction between the element electrode and element end surface of the surface acoustic wave device. CONSTITUTION:The stopping electrodes 2 and 3 which stop the surface acoustic wave from traveling straight by changing its direction are arranged between the element electrode and element end surface 1 of the surface acoustic wave device to scatter the traveling direction of the surface acoustic wave. Stopping electrodes 2 and 3 which are shifted in slit position are stacked in plural stages, and consequently a wave reaching the element end surface 1 has almost none of the initial straight traveling component left and is different in direction. Consequently, nearly the same result with the irregular reflection of the straight traveling wave is obtained by reflection on the element end surface 1. Further, the reflected wave on the element end surface 1 further passes through the slit of the stopping electrode, so the direction of the wave is further changed to evade the adverse influence of the reflected wave. The stopping electrodes can be formed in the same process with element electrodes of the surface acoustic wave device, so the cost is reduced by simplifying the process.
Patent•
11 Oct 2002
TL;DR: In this article, a Surface Acoustic Wave (SAW) resonator based transmitter exhibits stable bandwidth in a temperature controlled operating environment, for temperatures outside of the range of human body temperature, the output of the SAW-based transmitter is adjusted to provide reduced bandwidth.
Abstract: Radio frequency bandwidth from a far field transmitter of an implantable medical device is adjusted by controlling the data rate, the output power level, the transmitter supply voltage or combinations thereof. Adjustments are made on the basis of a sensed temperature, absence or presence of a lead or by way of wave shaping. A Surface Acoustic Wave (SAW) resonator based transmitter exhibits stable bandwidth in a temperature controlled operating environment. For temperatures outside of the range of human body temperature, the output of the SAW-based transmitter is adjusted to provide reduced bandwidth.
TL;DR: In this paper, the authors studied the propagation of surface waves on nanocrystalline diamond prepared by microwave plasma chemical vapor deposition (CVD) on silicon substrates, and concluded that this material is a highly attractive substrate material for SAW devices, possessing the high sound velocity of diamond but requiring less materials processing.
TL;DR: In this paper, the propagation modes of surface acoustic waves in AlN and GaN layers are identified for the case of the acoustic wave being confined in the epitaxial layers by the fast-velocity SiC substrate.
Abstract: The propagation modes of surface acoustic waves ~SAW! in AlN and GaN layers are identified for the case of the acoustic wave being confined in the epitaxial layers by the fast-velocity SiC substrate. Higher-order Rayleigh modes emerge when the SAW wavelength is reduced to be below the layer thickness. We also report on the observation of an extremely-high-velocity SAW mode, which exists when the SAW wavelength is about an order of magnitude larger than the layer thickness. These guided modes enable us to utilize SAW velocities which can be even larger than the Rayleigh velocity in the substrate while maintaining the large electromechanical coupling coefficient of the overlayer.
TL;DR: In this article, a surface acoustic wave (SAW) based sensor was used to characterize the sensitivity of a polymeric membrane to relative humidity variations in the range 0% to 90% of a platinum polyyne, namely poly-[1,4-dihexadecyloxy-2,5-diethynylbenzene-bis(triphenylphosphine) platinum(II)] (Pt-P-HDOB) membrane.
Abstract: The sensitivity to relative humidity (RH) variations in the range 0%–90% of a platinum polyyne, namely poly-[1,4-dihexadecyloxy-2,5-diethynylbenzene-bis(triphenylphosphine) platinum(II)] (Pt-P-HDOB) membrane was investigated by means of a surface acoustic wave (SAW) based sensor. A thin film of polymeric membrane was spin deposited on the free surface of the device and the resulting acoustic velocity and attenuation perturbations allowed the acoustic characterization of the membrane by means of the perturbation theory. The SAW sensor was able to reveal even very low (<10% RH) humidity conditions at room temperature, with high reproducibility, repeatability and stability.
TL;DR: In this paper, a novel process for fabricating ZnO/diamond/Si for a surface acoustic wave device is described, where the Si wafer is chemically etched by employing the SiO2 layer as a mask.
Patent•
30 Sep 2002TL;DR: In this article, a transducer is mounted on the acoustic cavity for generating an acoustic wave that is substantially trapped in the cavity, and a touch on the touch surface of the acoustic wave cavity absorbs acoustic wave energy and produces a detectable change in the impedance of the transducers.
Abstract: An acoustic wave switch includes a substrate (14) with an acoustic wave cavity (20) formed therein such that the mass per unit area of the acoustic cavity is greater than the mass per unit area of the substrate adjacent the cavity. A transducer (26) is mounted on the acoustic cavity (20) for generating an acoustic wave that is substantially trapped in the cavity. A touch on the touch surface (28) of the acoustic wave cavity absorbs acoustic wave energy and produces a detectable change in the impedance of the transducer. Various feedback mechanisms can be employed to provide a user with a tactile, audible and/or visual response indicating actuation of the switch by a touch.
TL;DR: In this article, Brillouin light scattering and surface acoustic wave spectroscopy are used to measure density, porosity and stiffness properties of nanoporous methylsilsesquioxane films of low-k value.
Abstract: Thin porous films with nanometer pore sizes are the subject of intense interest, primarily because of their reduced dielectric constant k. The lack of useful characterization tools and the reduction in film mechanical properties with increasing porosity have severely hindered their development and application. We show that both Brillouin light scattering and surface acoustic wave spectroscopy allow one to measure density, porosity and stiffness properties of nanoporous methylsilsesquioxane films of low-k value. Excellent correlations are observed among independent measurements of density, porosity and the Young’s modulus which show that the results obtained are reliable and reveal properties of the films which are difficult or impossible to obtain using other techniques.
Patent•
29 Aug 2002TL;DR: In this paper, a surface acoustic wave filter unit with three interdigital transducers arranged along the surface wave propagation direction is disposed on a piezoelectric substrate and reflectors are grounded.
Abstract: A surface acoustic wave filter unit having three interdigital transducers arranged along the surface acoustic wave propagation direction is disposed on a piezoelectric substrate. An unbalanced signal terminal and balanced signal terminals are provided for the surface acoustic wave filter unit. At least one of the three interdigital transducers is out of phase relative to the other interdigital transducers. Reflectors are arranged so as to sandwich the three interdigital transducers therebetween. The reflectors are grounded. Thus, a surface acoustic wave filter having a balance-to-unbalance conversion function and having high balance between the balanced signal terminals is achieved.