Introduction - If you have any usage issues, please Google them yourself
In mode analysis it is usually the primary goal to find a propagation constant. This
quantity is often, but not always, real valued if the analysis involves some lossy part,
such as a nonzero conductivity or an open boundary, the eigenvalue is complex. In
such situations, the real and imaginary parts have separate interpretations:
• The real part is the propagation constant
• The imaginary part is the attenuation constant, measuring the damping in space