Forums

linear phase iir filters

Started by shamganth August 26, 2003
sir,
iam doing my postgraduation in communication in south india at Anna
University. Iam doing my project in Linear phase IIR filters. I have
the base materials for Linear phase iir filters. I wish to implement
the Linear phase IIR filter system in Matlab. so yet i haven't get an
idea how to implement the system. If anyone came across those websites
and have the materials relates to the codings of Linear phase IIR
filters please reply.
thanks in advance.
shamganth@rediffmail.com (shamganth) writes:

> iam doing my postgraduation in communication in south india at Anna > University. Iam doing my project in Linear phase IIR filters. I have > the base materials for Linear phase iir filters.
Do the base materials include some philosopher's stone?
> I wish to implement > the Linear phase IIR filter system in Matlab. so yet i haven't get an > idea how to implement the system. If anyone came across those websites > and have the materials relates to the codings of Linear phase IIR > filters please reply.
On causal linear phase IIR digital filters Clements, M.A. Pease, J.W. Sch. of Electr. Eng., Georgia Inst. of Technol., Atlanta, GA; This paper appears in: Acoustics, Speech, and Signal Processing [see also IEEE Transactions on Signal Processing], IEEE Transactions on Publication Date: Apr 1989 On page(s): 479-484 Volume: 37, Issue: 4 More stuff from rb-j: http://aulos.calarts.edu/pipermail/music-dsp/1998-November/021137.html Ciao, Peter K. -- Peter J. Kootsookos "Na, na na na na na na, na na na na" - 'Hey Jude', Lennon/McCartney
shamganth wrote:
> sir, > iam doing my postgraduation in communication in south india at Anna > University. Iam doing my project in Linear phase IIR filters. I have > the base materials for Linear phase iir filters. I wish to implement > the Linear phase IIR filter system in Matlab. so yet i haven't get an > idea how to implement the system.
I've got a good idea: use the filtfilt() function. Regards, Andor
p.kootsookos@remove.ieee.org (Peter J. Kootsookos) wrote in message news:<s68vfsl113n.fsf@mango.itee.uq.edu.au>...
> shamganth@rediffmail.com (shamganth) writes: > > > iam doing my postgraduation in communication in south india at Anna > > University. Iam doing my project in Linear phase IIR filters. I have > > the base materials for Linear phase iir filters. > > Do the base materials include some philosopher's stone?
That's a succint formulation of my immediate reaction... I always thought that "[causal] IIR filter" and "linear phase" were contradicions in terms?
> > I wish to implement > > the Linear phase IIR filter system in Matlab. so yet i haven't get an > > idea how to implement the system. If anyone came across those websites > > and have the materials relates to the codings of Linear phase IIR > > filters please reply. > > On causal linear phase IIR digital filters > Clements, M.A. Pease, J.W. > Sch. of Electr. Eng., Georgia Inst. of Technol., Atlanta, GA; > > This paper appears in: Acoustics, Speech, and Signal Processing [see > also IEEE Transactions on Signal Processing], IEEE Transactions on > Publication Date: Apr 1989 > On page(s): 479-484 > Volume: 37, Issue: 4 > > More stuff from rb-j: > > http://aulos.calarts.edu/pipermail/music-dsp/1998-November/021137.html
While I haven't checked out the Clements & Pease paper, I don't understand what RBJ is talking about in the mentioned link, when he says "Truncated IIR". Isn't that, by definition, a FIR structure? For that matter, why would anyone want to make a linear phase IIR? Isn't it way easier to stick with the good ol' FIR? Or am I missing something? Rune
allnor@tele.ntnu.no (Rune Allnor) writes:

> p.kootsookos@remove.ieee.org (Peter J. Kootsookos) wrote in message news:<s68vfsl113n.fsf@mango.itee.uq.edu.au>... > > shamganth@rediffmail.com (shamganth) writes: > > > > > iam doing my postgraduation in communication in south india at Anna > > > University. Iam doing my project in Linear phase IIR filters. I have > > > the base materials for Linear phase iir filters. > > > > Do the base materials include some philosopher's stone? > > That's a succint formulation of my immediate reaction... I always thought > that "[causal] IIR filter" and "linear phase" were contradicions in terms?
Yes, that's always my immediate reaction.
> While I haven't checked out the Clements & Pease paper, I don't understand > what RBJ is talking about in the mentioned link, when he says "Truncated > IIR". Isn't that, by definition, a FIR structure? For that matter, why > would anyone want to make a linear phase IIR? Isn't it way easier to stick > with the good ol' FIR? > > Or am I missing something?
Effectively, you are correct, except that the implementation is IIR and you just stop the IIR after a certain time. Julius O. Smith has some stuff on his web-site: http://ccrma-www.stanford.edu/~jos/HornModeling/Truncated_Infinite_Impulse_Response.html Ciao, Peter K. -- Peter J. Kootsookos "Na, na na na na na na, na na na na" - 'Hey Jude', Lennon/McCartney
In article s68d6eshvmp.fsf@mango.itee.uq.edu.au, Peter J. Kootsookos at
p.kootsookos@remove.ieee.org wrote on 08/26/2003 19:00:

> allnor@tele.ntnu.no (Rune Allnor) writes: > >> p.kootsookos@remove.ieee.org (Peter J. Kootsookos) wrote in message >> news:<s68vfsl113n.fsf@mango.itee.uq.edu.au>... >>> shamganth@rediffmail.com (shamganth) writes: >>> >>>> iam doing my postgraduation in communication in south india at Anna >>>> University. Iam doing my project in Linear phase IIR filters. I have >>>> the base materials for Linear phase iir filters. >>> >>> Do the base materials include some philosopher's stone? >> >> That's a succint formulation of my immediate reaction... I always thought >> that "[causal] IIR filter" and "linear phase" were contradicions in terms? > > Yes, that's always my immediate reaction. > >> While I haven't checked out the Clements & Pease paper, I don't understand >> what RBJ is talking about in the mentioned link, when he says "Truncated >> IIR". Isn't that, by definition, a FIR structure?
well, it *is* an FIR. what you mean be "structure" might affect my answer. the term "Truncated IIR" is from Julius Smith as referened by Peter below. a TIIR is an FIR that has some structure that would remind one of an IIR. the simplest example of a TIIR is the one of a moving average filter. there are two ways of implementing it. one is with the straight forward FIR structure in which all coefs are 1/N (N is the number of samples getting averaged). the other structure is with a digital integrator but where the input has a delay line and adder that will subtract x[n-N] from the integrator input. not every TIIR is linear phase. some of them require cascading with one that has the opposite sense of decay or it requires segmentation, time-reversing the segment, TIIRing with an identical filter, flipping the result back around in time, and overlap-adding the result. it's a mess, but it's how you make a nearly IIR filter act with linear phase in a real-time app.
>> For that matter, why would anyone want to make a linear phase IIR?
i guess so that all frequencies are delayed equally.
>> Isn't it way easier to stick with the good ol' FIR?
usually it is. but if the number of taps are large, it's not always cheaper than the Truncated IIR approach.
>> Or am I missing something? > > Effectively, you are correct, except that the implementation is IIR > and you just stop the IIR after a certain time. > > Julius O. Smith has some stuff on his web-site: > > http://ccrma-www.stanford.edu/~jos/HornModeling/Truncated_Infinite_Impulse_Res > ponse.html > > Ciao,
can you guys down-under see Mars as well as us guys? it's even a little cloudy and i can see it really well. r b-j
robert bristow-johnson <rbj@surfglobal.net> writes:

> can you guys down-under see Mars as well as us guys? it's even a little > cloudy and i can see it really well.
Yup! It's pretty impressive. :-) Ciao, Peter K. -- Peter J. Kootsookos "Na, na na na na na na, na na na na" - 'Hey Jude', Lennon/McCartney
"Peter J. Kootsookos" wrote:
> > robert bristow-johnson <rbj@surfglobal.net> writes: > > > can you guys down-under see Mars as well as us guys? it's even a little > > cloudy and i can see it really well. > > Yup! It's pretty impressive. :-) > > Ciao, > > Peter K. > > -- > Peter J. Kootsookos > > "Na, na na na na na na, na na na na" > - 'Hey Jude', Lennon/McCartney
It's obviously a disk with binoculars, but the seeing hasn't beem good enough for me to see the polar caps with my 5" scope. Not likely tonight, either, but maybe tomorrow. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
On 26 Aug 2003 08:14:00 -0700, allnor@tele.ntnu.no (Rune Allnor)
wrote:

>p.kootsookos@remove.ieee.org (Peter J. Kootsookos) wrote in message news:<s68vfsl113n.fsf@mango.itee.uq.edu.au>... >> shamganth@rediffmail.com (shamganth) writes: >> >> > iam doing my postgraduation in communication in south india at Anna >> > University. Iam doing my project in Linear phase IIR filters. I have >> > the base materials for Linear phase iir filters. >> >> Do the base materials include some philosopher's stone? > >That's a succint formulation of my immediate reaction... I always thought >that "[causal] IIR filter" and "linear phase" were contradicions in terms? > >> > I wish to implement >> > the Linear phase IIR filter system in Matlab. so yet i haven't get an >> > idea how to implement the system. If anyone came across those websites >> > and have the materials relates to the codings of Linear phase IIR >> > filters please reply. >> >> On causal linear phase IIR digital filters >> Clements, M.A. Pease, J.W. >> Sch. of Electr. Eng., Georgia Inst. of Technol., Atlanta, GA; >> >> This paper appears in: Acoustics, Speech, and Signal Processing [see >> also IEEE Transactions on Signal Processing], IEEE Transactions on >> Publication Date: Apr 1989 >> On page(s): 479-484 >> Volume: 37, Issue: 4 >> >> More stuff from rb-j: >> >> http://aulos.calarts.edu/pipermail/music-dsp/1998-November/021137.html > >While I haven't checked out the Clements & Pease paper, I don't understand >what RBJ is talking about in the mentioned link, when he says "Truncated >IIR". Isn't that, by definition, a FIR structure? For that matter, why >would anyone want to make a linear phase IIR? Isn't it way easier to stick >with the good ol' FIR? > >Or am I missing something? > >Rune
Hi Rune, No, I don't think you're missing anything. I wonder if shamganth used the term "IIR" but really meant "recursive". There *ARE* linear-phase FIR recursive filters. They're called "frequency sampling filters", and I spent months studying those beasts. As it turns out, in some applications those freq sampling filters are more efficient than the standard Parks McClellan-designed filters! As for linear-phase IIR filters,... doesn't the filter's impulse response have to be symmetrical (or anti- symmetrical) to be linear phase? I'm wondering how you get an infinite impulse response to be symmetrical(?). I glanced at the http://ccrma-www.stanford.edu/~jos/HornModeling/Truncated_Infinite_Impulse_Response.html website, and could *not* quickly figure out how he gets the ratio of polynomials to collapse down to a single (FIR) polynomial. Shame on the author for not providing any filter block diagrams. He should have shown an example of a real-world impulse response before and after 'truncation', along with freq-domain plots. [-Rick-]
Rick,

you should meet Julius sometime.  he's a pretty cool dude with enough
knowledge of computer music and audio to scare the pants offa me.

r b-j

In article 3f4cd201.14205312@news.west.earthlink.net, Rick Lyons at
ricklyon@REMOVE.onemain.com wrote on 08/27/2003 11:54:
... 
> > I glanced at the > > http://ccrma-www.stanford.edu/~jos/HornModeling/Truncated_Infinite_Impulse_Res > ponse.html > > > website, and could *not* quickly figure out how he gets > the ratio of polynomials to collapse down to a single > (FIR) polynomial. Shame on the author for not providing > any filter block diagrams. He should have shown an > example of a real-world impulse response before and > after 'truncation', along with freq-domain plots. > > [-Rick-] > >