Search

A formulation based on the Laguerre polynomial method for surface acoustic waves was employed to investigate free-acoustic wave propagation in layered plates. The technique utilizes Legendre polynomials. Formulations are provided for both open-circuit and short-circuit surfaces. Phase velocity dispersion curves, attenuations, power distributions and field profiles were easily obtained from an algorithm easily executed on a computer employing commercial software.

Researchers examined the effectiveness of the Laguerre polynomial (LP) approach in calculating coupling coefficients in multilayered structures and semi-infinite substrates. They compared LP results with results obtained using the partial waves-based transfer-matrix method. They found that the LP method is useful for studying some multilayered structures, but it is not suitable for examining quantum well SAW-based devices. Examination of some semi-infinite substrates is possible using the LP method, but study of leaky surface acoustic waves is impossible.

This work presents the modeling of high contrast partially electroded resonators by means of a polynomial approach. This method allows easily solving the equations that govern the structure. The boundary, symmetry, and continuity conditions are automatically incorporated into the equations of motion by the use of delta functions for the variables stress (T) and electric displacement (D) and appropriate analytical expression forms for the independent variables, mechanical displacements (u), and electric potential ([lowercase_phi_synonym]). Structure symmetry was used to reduce the number of unknowns. For the zinc oxide (ZnO) resonator in extreme geometrical cases (thin plate and bar cases), a good agreement was obtained between the results of the proposed polynomial approach and those of an analytical approach for both the modal and harmonic analyses. The proposed polynomial approach was used to calculate the 2D resonator electrical admittance (full and partial metallization) near the 1D thickness fundamental mode, and the results highlight the presence of spurious modes. Influence of the metallization rate on the number of spurious modes in the bandwidth is studied. This model can also easily calculate the electromechanical coupling coefficient and the field profiles. Illustrations for both electromechanical coupling coefficient and particle displacement profiles are given for aluminium nitride (AlN), lead zirconate titanate, and ZnO resonators. [ABSTRACT FROM AUTHOR]

A bidimensional analysis of 6 mm hexagonal resonators is described using a double orthonormal basis set for the expansion of field quantities. The analysis takes into account the electrical voltage source and by means of a unique formalism along with a single calculation restitutes all the types of resonance whatever the thickness to width ratio value through either modal solutions or electrical impedance. An illustrative example gives the capabilities of the method to investigate spurious modes in laterally bounded resonators. [ABSTRACT FROM AUTHOR]

Research was conducted to examine the surface acoustic waves (SAWs) and other acoustic modes propagating in the (110) plane of Li2B4O7 using the effective surface permittivity (ESP). The velocity of all piezoactive SAWs, both pseudo and true, and surface skimming bulk waves were numerically determined by calculating the ESP as a function of acoustic trace slowness. All the quantitative results and conclusions were obtained from the numerical methods developed.

A theoretical study concerning a GaAs-Ga1-xAlx As acousto-electrooptic (AEO) modulator is presented. This study deals with the effects of electric and strain fields generated by a piezoactive surface acoustic wave (SAW) on the optical absorption edge, acoustical field components decrease with depth and thus limit device performances. An optimization based on an additional ZnO layer and on technological parameters fitting, well width and potential barrier height, is proposed [ABSTRACT FROM PUBLISHER]

Surface acoustic wave (SAW) technology based on lithium niobate/diamond/silicon multilayered structures has been investigated due to the large demand of frequency filters for communication systems, particularly for cellular phones. Thick LiNbO[sub 3] layers (∼1 µm) with a good morphology, i.e., surface roughness lower than 10 nm have been grown at 490 °C on diamond-coated silicon substrates by multistep rfmagnetron sputtering. A SAW devices operating at 300 MHz was designed and fabricated in order to validate the proposed structure; in particular, our main objective was to verify the high velocity in the layered structure. Preliminary filter responses were very promising: the SAW velocity was estimated to 8200 m/s and the coupling factor was K²∼0.93%. The film growth, the technology, and the electrical measurements are described in this letter. [ABSTRACT FROM AUTHOR]