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
Analog to FIR filter design method
Started by ●July 1, 2004
Reply by ●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 BlackProbably 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 ●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 BlackDo 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 ●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 ●July 1, 20042004-07-01
Jon Harris wrote:> "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.
