> "Suodatin Pussi" <Suodatin_Pussi@kokonaisuutena.hotmail.com> wrote in message
> news:40e47e2a$0$65124$e4fe514c@news.xs4all.nl...
>> philblack wrote:
>> >
>> > What is the best method to convert a analog filter design to a FIR
>> > filter design? Lets say I have the tranfer function in the S domain
>> > of a analog filter and I want to design a FIR filter with the same
>> > freq response. I know there are many ways to do this for IIR filters
>> > but I would like a more predictable phase response.
>>
>> Probably not the best but if you get the impulse response of the filter
>> you could fft it, alter the phase and ifft it.
>
> Why would you want/need to alter the phase?
>
For me an s-filter has an predictable phase response (but 'tied' to the
amplitude response) so I read it as philblack would like to keep the
ampitude response as is but change the phase response. but maybe he's
got other reasons to use a fir.
Reply by Jon Harris●July 1, 20042004-07-01
"Suodatin Pussi" <Suodatin_Pussi@kokonaisuutena.hotmail.com> wrote in message
news:40e47e2a$0$65124$e4fe514c@news.xs4all.nl...
> philblack wrote:
> >
> > What is the best method to convert a analog filter design to a FIR
> > filter design? Lets say I have the tranfer function in the S domain
> > of a analog filter and I want to design a FIR filter with the same
> > freq response. I know there are many ways to do this for IIR filters
> > but I would like a more predictable phase response.
>
> Probably not the best but if you get the impulse response of the filter
> you could fft it, alter the phase and ifft it.
Why would you want/need to alter the phase?
Reply by Tim Wescott●July 1, 20042004-07-01
philblack wrote:
> Anyone,
>
> What is the best method to convert a analog filter design to a FIR
> filter design? Lets say I have the tranfer function in the S domain
> of a analog filter and I want to design a FIR filter with the same
> freq response. I know there are many ways to do this for IIR filters
> but I would like a more predictable phase response.
>
> Phil Black
Do an ifft on the magnitude of the frequency response -- you'll get back
the coefficients for your FIR. It'll be long, though -- you may be
better off just designing a new one from the requirements for the
original, if you can reverse-engineer them from the current response.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply by Suodatin Pussi●July 1, 20042004-07-01
philblack wrote:
> Anyone,
>
> What is the best method to convert a analog filter design to a FIR
> filter design? Lets say I have the tranfer function in the S domain
> of a analog filter and I want to design a FIR filter with the same
> freq response. I know there are many ways to do this for IIR filters
> but I would like a more predictable phase response.
>
> Phil Black
Probably not the best but if you get the impulse response of the filter
you could fft it, alter the phase and ifft it.
Reply by philblack●July 1, 20042004-07-01
Anyone,
What is the best method to convert a analog filter design to a FIR
filter design? Lets say I have the tranfer function in the S domain
of a analog filter and I want to design a FIR filter with the same
freq response. I know there are many ways to do this for IIR filters
but I would like a more predictable phase response.
Phil Black