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Nonlinearity can give rise to intermodulation distortions in surface acoustic wave (SAW) devices operating at high input power levels. To understand such undesired effects, a finite element method (FEM) simulation model in combination with a perturbation theory is applied to find out the role of different materials and higher order nonlinear tensor data for the nonlinearities in such acoustic devices. At high power, the SAW devices containing metal, piezoelectric substrate, and temperature compensating (TC) layers are subject to complicated geometrical, material, and other nonlinearities. In this paper, third-order nonlinearities in TC-SAW devices are investigated. The materials used are LiNbO 3 -rot128YX as the substrate and copper electrodes covered with a SiO 2 film as the TC layer. An effective nonlinearity constant for a given system is determined by comparison of nonlinear P-matrix simulations to third-order intermodulation measurements of test filters in a first step. By employing these constants from different systems, i.e., different metallization ratios, in nonlinear periodic P-matrix simulations, a direct comparison to nonlinear periodic FEM-simulations yields scaling factors for the materials used. Thus, the contribution of the different materials to the nonlinear behavior of TC-SAW devices is obtained and the role of metal electrodes, substrate, and TC film are discussed in detail.
In a SAW device comprises a SAW chip bearing a SAW transducer arranged within a first signal line parasitic signals due to higher harmonics of the operating frequency of the SAW devices are electrically eliminated by compensating means comprising at least one second signal line having means for producing a cancelling signal different in sign or phase to the parasitic signal, or a shunt line to electrically connect the SAW transducer to a back side metallization of the SAW chip.
In einer SAW-Vorrichtung, welche einen SAW-Chip umfasst, der einen SAW-Wandler aufweist, welcher innerhalb einer ersten Signalleitung angeordnet ist, werden Parasitärsignale infolge höherer Harmonischer der Betriebsfrequenz der SAW-Vorrichtungen durch Kompensationsmittel elektrisch beseitigt, welche zumindest eine zweite Signalleitung mit Mitteln zum Erzeugen eines Aufhebungssignals, das im Vorzeichen oder in der Phase vom Parasitärsignal verschieden ist, oder eine Nebenschlussleitung zum elektrischen Verbinden des SAW-Wandlers mit einer rückseitigen Metallisierung des SAW-Chips umfassen.
In a recent paper it has been shown that the effective nonlinear constant which is used in a P-Matrix approach to describe third-order intermodulation (IMD3) in surface acoustic wave (SAW) devices can be obtained from finite element (FEM) calculations of a periodic cell using nonlinear tensor data [1]. In this paper we extend this FEM calculation and show that the IMD3 of an infinite periodic array of electrodes on a piezoelectric substrate can be directly simulated in the sagittal plane. This direct approach opens the way for a FEM based simulation of nonlinearities for finite and generalized structures avoiding the simplifications of phenomenological approaches.
In the present work, nonlinearities in temperature
compensating (TC) SAW devices are investigated. The materials
used are LiNbO3-rot128YX as the substrate and Copper electrodes covered with a SiO2-layer as the compensating layer.
In order to understand the role of these materials for the
nonlinearities in such acoustic devices, a FEM simulation model
in combination with a perturbation approach [1] is applied.
The nonlinear tensor data of the different materials involved
in TC-SAW devices have been taken from literature, but were
partially modified to fit experimental data by introducing scaling factors. An effective nonlinearity constant is determined
by comparison of nonlinear P-matrix simulations to IMD3
measurements of test filters. By employing these constants in
nonlinear periodic P-matrix simulations a direct comparison to
nonlinear periodic FEM-simulations yields the scaling factors for
the material used. Thus, the contribution of different materials
to the nonlinear behavior of TC-SAW devices is obtained and
the role of metal electrodes is discussed in detail
Die Veränderungen in der Energieversorgung führen zu einer neuen Systemarchitektur der Stromversorgung, die nur durch einen massiven Einsatz von Informations- und Kommunikationstechnologien (IKT) bewältigt werden kann und meist als „Smart Grid“ bezeichnet wird. Während es bereits umfangreiche Forschungsarbeiten und Demonstrationsprojekte zu einzelnen technologischen Komponenten gibt, existieren noch wenige Überlegungen, in welchen technologischen Schritten eine Migration hin zu Smart Grids durchgeführt werden sollte, die sowohl betriebstechnisch zukunftssicher ist, als auch marktgetriebene Innovationen begünstigt. Der Beitrag veranschaulicht die Herleitung solcher Migrationspfade im Rahmen eines schrittweisen Vorgehens. Zunächst werden Zukunftsszenarien für das Jahr 2030 konstruiert, um die maßgeblichen, oft auch nichttechnischen Einflussfaktoren auf das Smart Grid zu identifizieren. Darauf aufbauend werden die wesentlichen IKT-bezogenen Technologiefelder und ihre Zuordnung zu den Domänen der Energiewirtschaft beschrieben. Für jedes Technologiefeld werden die in den nächsten zwei Jahrzehnten denkbaren Entwicklungsstufen ermittelt und deren Abhängigkeit untereinander analysiert. Die gemeinsame Betrachtung von Szenarien, der Entwicklungsstufen der Technologiefelder und deren Interdependenzen führen schließlich zu einer Roadmap, welche die Migrationspfade in das Smart Grid beschreiben. Es lassen sich drei Entwicklungsphasen erkennen: Die Konzeptionsphase, die Integrationsphase und die Fusionsphase. Die präsentierten Ergebnisse entstammen dem Projekt „Future Energy Grid – Migrationspfade ins Internet“, welches vom Bundesministerium für Wirtschaft und Technologie im Rahmen des E-Energy-Programms (Förderkennzeichen 01ME10012A und 01ME10013) gefördert wurde.
For an elastic medium containing a homogeneous distribution of micro-cracks, an effective one-dimensional stress-strain relation has been determined with finite element simulations. In addition to flat micro-cracks, voids were considered that contain a Hertzian contact, which represents an example for micro-cracks with internal structure. The orientation of both types of micro-cracks was fully aligned or, for flat micro-cracks, totally random. For micro-cracks with Hertzian contacts, the case of random orientation was treated in an approximate way. The two types of defects were found to give rise to different degrees of non-analytic behavior of the effective stress-strain relation, which governs the nonlinear propagation of symmetric (S0) Lamb waves in the long-wavelength limit. The presence of flat micro-cracks causes even harmonics to grow linearly with propagation distance with amplitudes proportional to the amplitude of the fundamental wave, and gives rise to a static strain. The presence of the second type of defects leads to a linear growth of all harmonics with amplitudes proportional to the power 3/2 of the fundamental amplitude, and to a strain-dependent velocity shift. Simple expressions are given for the growth rates of higher harmonics of S0 Lamb waves in terms of the parameters occurring in the effective stress-strain relation. They have partly been determined quantitatively with the help of the FEM results for different micro-crack concentrations.
Existing ultrasonic stress evaluation methods utilize the acoustoelastic effect for bulk waves propagating in volume, which is unsuitable for a surface treated material, possessing a significant variation in material properties with depth. With knowledge of nonlinear elastic parameters – third-order elastic constants (TOEC) close to the surface of the sample, the acoustoelastic effect might be used with surface acoustic waves. This work is focused on the development of an independent method of TOEC measurement using the effect of nonlinear surface acoustic waves scattering – i.e. the effect of elastic waves interaction in a nonlinear medium.
In this paper, the possible three wave interactions of surface guided waves and bulk waves are described and formulae for the efficiency of harmonic generation and mode mixing are derived. A comparison of the efficiency of surface waves scattering in an isotropic medium for different interaction types is carried out with the help of nonlinear perturbation theory. First results for surface and bulk wave mixing with known second- and third-order elastic constants are shown.