Sun Aug 8 07:30:28 CEST 2010

Schroeder phases and quadratic residue diffusors.

What is the idea behind a quadratic residue diffusor (QRD)?  What is
the link with Schroeder and Newman phases?

( Is there any link with the "maximal irrationality" of the golden
ratio.  Max. irr. here means partial fraction expansion is all ones
which means that rational approximation converges as slow as
possible. )

In [2] it is mentioned that surprisingly, the DFT of the exponentiated
sequence (amplitude 1 and n^2 mod p used as the _phase_) has a
constant magnitude.

Why is this?

[1] http://www.dpi.physik.uni-goettingen.de/~mrs/Vortraege/Remembering-the-Good-Days-at-Bell-Laboratories-2004/index.html
[2] https://ccrma.stanford.edu/~kglee/pubs/2dmesh_QRD_rev1/node2.html