Re: outstanding changesets

[Ben Abbott]

On Feb 1, 2009, at 1:56 PM, Daniel J Sebald wrote:

> Ben Abbott wrote:
> > On Jan 29, 2009, at 1:50 AM, Søren Hauberg wrote:
> > > ons, 28 01 2009 kl. 22:13 -0500, skrev John W. Eaton:
> > >
> > > > Does Matlab produce the same result?
> > >
> > >
> > > Matlab produces the attached pdf
> > >
> > > Søren
> > > <matlab_freqz.pdf>
> > ? ... that is not what I expected. My impression was the Matlab   
> > unwrapped the phase in such a way that only positive delays would   
> > result. However, in this example, it appears to be opposite.
> > Any idea what they are doing?
>
> To "unwrap the phase" does not mean disallowing negative, it means  
> to remove any 360 degree jumps from the phase which were created as  
> a consequence of the modular arithmetic of phase angles.  Note that  
> if there are 180 degree phase shifts, those stay because they are  
> actual phase jumps.
>
> Dan

Hi Dan,

What I've inferred is that Matlab's implementation favors unwrapping  
the phase so that the phase slope is negative (downward sloping), and  
the delay is positive.

See the examples at the link below.

        http://hauberg.org/wiki/doku.php?id=freqz

Ben