f



Filter Group Delay

The Matlab command 'grpdelay' is restricted to digital filters only.
Does there exist some counterpart to 'grpdelay' that operates in the
analog domain?

Some Matlab commands have separate versions for the analog and
digital domains, and I wonder why 'grpdelay' does not. For example,
the 'butter' command to generate Butterworth filter coefficients has
digital and analog versions. The analog version is useful for
understanding the stand-alone characteristics of a proposed filter,
i.e., the characteristics that are independent of a particular
sampled data record. The digital version is useful when one wishes
to operate on actual data.
0
6/12/2007 9:01:58 PM
comp.soft-sys.matlab 211266 articles. 18 followers. lunamoonmoon (258) is leader. Post Follow

2 Replies
463 Views

Similar Articles

[PageSpeed] 2

Dear Mark,

I suppose the most simplest explanation is that group delay is
expressed in samples, which is irrelevant for analogue systems as
there is no sampling and casuality constraints. Of course, group
delay is simply the negative of first derviative of the phase w.r.t
frequency.

I hope that this helps!

Regards,
Sanjeev.

--------------------------------------------
Dr. Sanjeev Sarpal CEng, MIET
Advanced Solutions Nederland
website: <http://www.advancedsolutions.org>

 Proulx wrote:
>
>
> The Matlab command 'grpdelay' is restricted to digital filters
> only.
> Does there exist some counterpart to 'grpdelay' that operates in
> the
> analog domain?
>
> Some Matlab commands have separate versions for the analog and
> digital domains, and I wonder why 'grpdelay' does not. For
> example,
> the 'butter' command to generate Butterworth filter coefficients
> has
> digital and analog versions. The analog version is useful for
> understanding the stand-alone characteristics of a proposed filter,
> i.e., the characteristics that are independent of a particular
> sampled data record. The digital version is useful when one wishes
> to operate on actual data.
0
6/14/2007 10:50:42 AM
On 12 Jun, 23:01, "Mark Proulx" <mark.p.pro...@boeing.com> wrote:
> The Matlab command 'grpdelay' is restricted to digital filters only.
> Does there exist some counterpart to 'grpdelay' that operates in the
> analog domain?

I don't know exactly how the command is implemented in matlab,
but there is no reason why an analog version should not exist.
The relation between the group delay and the spectrum is the same
in both cases, so the same formulas apply.

The difference is how to compute the spectrum. While the DFT
suits computations in discrete-time domain, one needs to compute
the Fourier Series in continuous-time domain.

IF the group delay is computed in separate stages as first
computing a spectrum and then compute the group delay
from that, it is no problems to substitute the spectrum
computations and get the group delay for the analog system.

Rune

0
allnor (8509)
6/14/2007 12:09:40 PM
Reply: