Fri Apr 19 20:16:15 EDT 2013

IRT - impulse response truncation & Gibbs

There the Dirichlet function shows up (not the sinc function!), which
is the in-phase sum of N complex exponentials. A.k.a. discrete
summation formula.

The integral of the Dirichlet function comes back in the explanation
of the Gibbs phenomenon for IRT filters.  Due to this, IRT filters can
never exceed a certain pass/stop-band spec.