Max-flat min-phase filters

On May 19, 1:00&#4294967295;pm, Tim Wescott <t...@seemywebsite.com> wrote:
> On 05/19/2011 09:42 AM, mcode wrote:
>
> > Hello!
>
> > Does anyone have references on (lowpass) filters with maximally flat
> > magnitude at DC and minimum phase? A first look only turned up linear-
> > phase and reduced-delay designs. I'm particularly interested in FIR
> > right now, but also IIR.
>
> In the continuous-time world that's a Bessel filter. &#4294967295;I don't know if
> there's an equivalent IIR sampled-time filter.
>
> In FIR, a filter with a Gaussian shape may get you that.
>
> --
>
> Tim Wescott
> Wescott Design Serviceshttp://www.wescottdesign.com
>
> Do you need to implement control loops in software?
> "Applied Control Theory for Embedded Systems" was written for you.
> See details athttp://www.wescottdesign.com/actfes/actfes.html

Bessel filter is maximally flat in group delay.  Butterworth is
maximally flat in magnitude.

Dirk

Okay, I underspecified the problem. What I really wanted to know is
whether the lit has a *closed form* for FIR with *independent*
flatness degrees (n zero tangents at DC, k roots at Nyquist) and
minimum phase. After reading the classic study of Selesnick and
Burrus, I thought someone might have cracked the mp special case. But
I just found this paper, whose existence I guess implies a definitive
No: http://dx.doi.org/10.1016/S0196-8858(03)00022-8


Thanks folks,
Martin