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From: Laron on 6 Jan 2010 01:55
Hi,
When simulate the FIR filter response, run interp(Matrix,n) in matlab,
the maximum of Matrix is 1,but the response is larger than 1?
I wonder know why this could be happen and how to degrade this
effect?

B. R.
Thanks.
From: Tim Wescott on 6 Jan 2010 02:52
On Wed, 06 Jan 2010 00:55:55 -0600, Laron wrote:

> Hi,
> When simulate the FIR filter response, run interp(Matrix,n) in
> matlab,
> the maximum of Matrix is 1,but the response is larger than 1?
> I wonder know why this could be happen and how to degrade this
> effect?

At a guess, Matlab is using a stiff bandpass filter and you're seeing
Gibbs phenomenon. Does Matrix have sharp edges?

Read the fine manual, see if you can chose a different filter for interp.

--
www.wescottdesign.com
From: Laron on 6 Jan 2010 03:19
>At a guess, Matlab is using a stiff bandpass filter and you're seeing
>Gibbs phenomenon. Does Matrix have sharp edges?
>
>Read the fine manual, see if you can chose a different filter for
interp.
>
>--
>www.wescottdesign.com
>
Matrix do have sharp edges like [1 0 1 1 0 1] etc, for rasied cosine
filter application.

Thanks.


From: Mark on 6 Jan 2010 08:25
On Jan 6, 3:19 am, "Laron" <jason.pi...(a)inbox.com> wrote:
> >At a guess, Matlab is using a stiff bandpass filter and you're seeing
> >Gibbs phenomenon.  Does Matrix have sharp edges?
>
> >Read the fine manual, see if you can chose a different filter for
> interp.
>
> >--
> >www.wescottdesign.com
>
> Matrix do have sharp edges like [1 0 1 1 0 1] etc, for rasied cosine
> filter application.
>
> Thanks.

search around over at rec.audio.pro.

there have been discussions in the past about how/why a reconstructed
waveform can exceed the max digital value.

Mark
From: Tim Wescott on 6 Jan 2010 09:32
On Wed, 06 Jan 2010 02:19:55 -0600, Laron wrote:

>>At a guess, Matlab is using a stiff bandpass filter and you're seeing
>>Gibbs phenomenon. Does Matrix have sharp edges?
>>
>>Read the fine manual, see if you can chose a different filter for
> interp.
>>
>>--
>>www.wescottdesign.com
>>
> Matrix do have sharp edges like [1 0 1 1 0 1] etc, for rasied cosine
> filter application.
>
> Thanks.

Reconstruction filters can ring. Filters that ring, when presented with
inputs with sharp edges, can ring strongly enough to exceed the bounds of
the input.

If you understand how the Matlab function works then you will know
whether or not you can change the properties of the reconstruction filter
it uses. If you don't, well, Matlab's documentation should tell you.

If you know how to change Matlab's reconstruction filter, you're home
free.

If you don't, then if you understand how the reconstruction process works
it's pretty easy to do the whole thing yourself, with whatever filter you
want to use.

Do you understand how reconstruction works?

--
www.wescottdesign.com
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