Time filter

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Wolcott, CT, United States

Hecht F.,University Pierre and Marie Curie | Ventura P.,University of Lorraine | Dufilie P.,Phonon Corporation
Journal of Computational Physics | Year: 2013

This paper proposes a new numerical coupled Finite Element Method/Boundary Integral Equations (FEM/BIE) technique which allows the 2D physical simulation of Surface Acoustic Waves (SAWs) transducers infinitely periodic in one direction. This new technique could be generalized to various periodic acoustic 2D simulations. This new method uses an original Variational Formulation (VF) which formally includes harmonic periodic boundary conditions, and, efficient boundary integral formulations allowing to account for the semi-infinite dielectric and piezoelectric spaces. In the case of the piezoelectric semi-space, the Green's functions are efficiently computed using Fahmy-Adler's method [8]. Only periodic boundary conditions are needed, which greatly simplifies the code implementation. This numerical model has been developed to analyze an Inter-Digital Transducer (IDT) with complex electrode shape (unburied, buried or raised electrodes). The use of buried electrodes in SAW transducer designs on quartz has important advantages when compared with unburied metal electrodes on the surface. One important property is the suppression of transverse waveguide modes in transducers. A second advantage is the ability to use thicker metal thereby reducing the resistive losses. Buried electrodes have also been shown to increase the quality factor of Surface Transverse Wave (STW) resonators [15]. This numerical model is a very useful tool for optimizing the electrode geometry. Analysis of raised electrodes is useful for predicting the effects of Reactive Ion Etch (RIE) on the SAW or STW electrical filter characteristics. RIE is commonly used as a frequency trimming technique for SAW or STW filters on Quartz. The first part of the paper presents the theory, and, the second part is devoted to numerical validations and numerical results. © 2013 Elsevier Inc.

Ventura P.,PV RandD Consulting | Hecht F.,University Pierre and Marie Curie | Dufilie P.,Phonon Corporation
Proceedings - IEEE Ultrasonics Symposium | Year: 2010

The use of buried electrodes in SAW designs on quartz has importantadvantages when compared with unburied metal electrodes on the surface. Oneimportant property is the suppression of waveguide modes in transducers. Asecond advantage is the ability to use thicker metal thereby reducing theresistive losses. A numerical model for the buried electrodes is a useful toolfor optimizing the buried electrode geometry. The numerical model can beextended to include the case of raised electrodes where a given depth ofnon-metalized substrate has been removed by reactive ion etch (RIE). This paperdescribes a new numerical model that is used to simulate the electro-acousticalbehavior of a single periodic buried (or partially buried) IDT. In order to takeinto account the buried part of the electrode, it is necessary to include inthe FEM domain the buried electrode along with part of the piezoelectricsubstrate, and of the dielectric domain above the electrode. The dielectric andthe piezoelectric semi-spaces are taken into account with boundary integralformulations while Bloch-Floquet's conditions are expressed on the lateralboundaries using an original and efficient method. P matrix parameters for asingle periodic buried IDT will be shown, as well as comparisons with buried IDTexperimental data. © 2010 IEEE.

Ventura P.,PV R and D Consulting | Dufilie P.,Phonon Corporation | Hecht F.,University Pierre and Marie Curie
IEEE International Ultrasonics Symposium, IUS | Year: 2011

STW resonators on quartz are preferred over SAW due to their superior acceleration sensitivity, power handling, improved aging behavior, and 60% higher velocity. The achieved resonator Q at high frequencies using a metallic grating is lower than expected, mainly due to bulk mode scattering losses. The purpose of this study is to find the grating geometry which can reduce the propagation attenuation of the STW. © 2011 IEEE.

Phonon Corporation | Date: 2013-01-15

A surface acoustic wave (SAW) device comprising at least one heating element formed on the substrate; at least one temperature sensor having a first electric component on the substrate whose resistance varies with the temperature of the substrate and a second electric component whose resistance does not vary; and a temperature controller including an operational amplifier bonded in thermally conductive relationship to the substrate. The operational amplifier is responsive to the output of the temperature sensor to apply power to the heating element and thereby maintain the temperature of the substrate within a predetermined temperature range. The transducer, heating element, and first component are monolithically formed on the substrate, and only three electrical connections are on the substrate at voltage to off-SAW die points.

Ventura P.,University of Lorraine | Dufilie P.,Phonon Corporation | Hecht F.,University Pierre and Marie Curie
IEEE International Ultrasonics Symposium, IUS | Year: 2014

Low loss SAW filters sometimes require a structure with a complex geometry in order to improve the electro-acoustic response (coupling coefficient, reflection coefficient, static capacitance). In the case of complex electro-acoustic cells (like Hanma-Hunsinger cells), it is necessary to obtain the mixed matrix parameters from the analysis of the entire multi-electrode electro-acoustic cell. Typically, the analysis is made for the cell in an infinite periodic array of identical cells using periodic boundary conditions. For each mixed matrix parameter, like the reflectivity or the piezoelectric coupling, the amplitude and the phase need to be known with a good accuracy in order to obtain good SAW filter designs. At the 2013 IEEE Ultrasonics Symposium, an original coupled Finite Element Model / Boundary Integral Equation (FEM/BIE) was presented which computes the harmonic admittance of an infinite array of aperiodic multi-electrode cells. In this paper, we will focus on extracting accurate mixed matrix parameters of Hanma-Hunsinger electro-acoustic cells. Numerical data will be given for an interesting six electrodes elementary cell structure called SFT and modified USFT. Applications in the design of SAW filters are shown. © 2014 IEEE.

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