SlownessBuddy is a program designed to obtain slowness curves for acoustic waves in a piezoelectric substrate, and this should normally be the only reason to use it. The program comes with a windows interface, but also launches several DOS programs when it comes to finite element analysis (this shortcoming is caused by the use of Modulef in its present version).
SlownessBuddy can compute slowness curves in the following cases:
- Bulk waves
- SAW and PSAW on either free or metallized surfaces
- SAW and PSAW under a thick aluminum layer
- SAW and PSAW in a (thick) grating
In any case SlownessBuddy will only output text files containing data in columns (it will not plot anything, but the output is formatted to be plotted with any *good* plotting program such as gnuplot). The text files contain the following information (except for the mixed matrix estimation case):
- Angle of phase
- Slowness (inverse of the phase velocity)
- Attenuation
- Coupling strength
- Beam-steering angle (angle between group or Poynting vector to phase wave-vector)
- GAMMA parameter (derivative of the beam-steering angle with respect to the phase angle)
Please keep in mind the following important facts:
- The axis convention used in SlownessBuddy is the so-called TMX-convention defined by Jean Desbois, in which axis x1 is the propagation direction for a zero phase angle, AXIS x2 ENTERS INTO THE SUBSTRATE, and axis x3 is the transverse direction. A shortcoming of this convention is that the PHASE ANGLE AND THE BEAM-STEERING ANGLE ARE TO BE UNDERSTOOD AS MINUS THE VALUES GIVEN IN MANY ARTICLES AND BOOKS. However, GAMMA is not affected by this sign convention. Note also that the cut is defined by the IEEE'49 standard in the usual coordinate system and is not affected either.
- THERE EXISTS NO UNIQUE NOR GOOD DEFINITION FOR THE COUPLING STRENGTH. The measures used in SlownessBuddy are explained in the SlownessBuddy1.2.pdf technical paper accompanying the distribution.