By Clemens C. W. Ruppel
A part of a set of 14 experiences of quite a lot of issues in acoustic wave expertise, aimed toward the clinical viewers. beneficial properties seven really good papers in all, discussing problems with observed units, from Green's services to instant observed sensor platforms.
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At high frequencies the situation is opposite: the theoretical velocity is too high and the simulated peaks are predicted at too high frequencies. So, the velocity dispersion causes "accordion"-type mismatch between the theory and measurement. This mismatch may be easily corrected by the introduction of dispersion in the wave velocity as follows: v(f)=vo(l-D±^y (89) Here /o, Ao, and VQ are the frequency, wavelength and velocity of the wave, respectively, measured at the center frequency of the Bragg stopband, and D is a parameter of the order of unity.
4. Limitations The simple system of linear equations (44) forms the core of the COM model. The equations take into account the multiple reflections and acoustoelectric interaction between the SAW and the charges on electrodes. Because of this the equations allow the modeling of a large variety of SAW devices. In spite of its intrinsic simplicity the COM model can be astonishingly precise for narrow band devices, provided that the explicit COM parameters are determined accurately. Meanwhile, one should remember that the simplicity of the COM equations requires numerous approximations.
Furthermore, complex-valued wavenumbers have to be considered, which is somewhat problematic in the Green's function methods and requires additional assumptions on the continuation of the Green's function into the complex plane. 8 7 ' 8 8 Alternatively to the eigenmodes, the generation problem may be analyzed: the system is modeled driven by a voltage source and the interest is in the currents on the electrodes. Since the generation problem more resembles practical experiments, the results of the generation problem are easier to interpret that those of the eigenmode analysis.