For?the?simple?reason?that?I?am?more?accustomed?to?problems?in?optics?and?elastic?wave?propagation,?I?did?not?think?to?consult?the?superb?"Theory?and?Computation?of?Electromagnetic?Fields"?by?JIang-Ming?Jin?which?I?have?in?the?2nd?edition.
Jin provides a very clear description of the properties of metamaterials in section 4.2.5 and plane wave reflection and transmission between right and left handed media in 4.4.4 including a figure showing the geometrical optics approximation to a left handed slab embedded between two right handed half spaces with a point source in the right handed medium.
If one takes the normal definition of refractive index as the ratio of the phase velocity, this does indeed result in a negative refractive index. The power flows away from the source, but the phase velocity is sign reversed in a left handed medium. Therefore my assertion that the refractive index can never be negative is incorrect.
The topic of the reflection and transmission characteristics of metamaterials is quite interesting and I welcome further discussion.
However, that does not change my assessment of Daniel Marks' post. I was very specific in my initial post that the issue of concern was minimum phase vs zero phase impulse response filters.
That issue is of major importance in the digital filtering in a DSO. All the DSOs I have examined including recent high end models from Keysight and Rohde & Schwartz employ a zero phase sinc interpolator and produce non-causal displays when fed a 100 ns minimum phase impulse.
Have Fun!
Reg
theory?in
