Re: Design of FIR filter with Sharp Transition and High Stop Band Attenuation
- From: "Bhaskar Thiagarajan" <bhaskart@xxxxxxxx>
- Date: Wed, 18 Jan 2006 16:50:04 -0800
"gaurav811" <gaurav811@xxxxxxxxx> wrote in message
news:EPmdnVQGUJPjQ1PeRVn-rA@xxxxxxxxxxxxxxx
> Hi
>
> I have to design a FIR filter with very steep transition at cutoff and
> high stop ban attenuation. FIR bcoz I need linear phase. I have matlab
> available. Fdatool is useless since its FIR dont have a good transition.
It's only as good as it's user.
> In literature search I came by papers talking about Sharp transition FIR`s
> using Frequency response masking and multirate filters. I wanted to know
if
> someone has any experience with these filters ? I am going to try to
> implement these and wanted to know what issues/problems I can face and are
> these papers claims any good.
What are your specs. Very steep isn't much of a spec.
> If you also know of some technique for implementing sharp transition FIR`s
> with low number of coeff`s let me know. Also if you know some
material/book
> that might help me with this point it to me.
Sharp transition FIRs and low number of coeffs don't go together. You might
be able to get *sharper* transitions given a certain number of coeffs using
some creative filter design but if you are looking for an order of magnitude
improvement, you are out of luck.
Multi-rate techniques help achieve a fairly sharp cutoff using oversampling
without putting too much of a computing burden (caused by a high number of
coeffs) but this involves designing multiple filters. There are several
references that you can use to learn about multi-rate filters - I'd start
with http://dspguru.com/info/faqs/mrfaq.htm
Cheers
Bhaskar
.
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