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Subject: Re: mfilt.iirinterp( )
Date: Tue, 18 Sep 2007 12:19:48 +0000 (UTC)
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Thanks Honglei,

Your example helped and with some further experimentation I 
was able to get things working.

Good idea regarding the documention enhancement request.
 
Thanks again,
Stephen 


"Honglei Chen" <hchen@mathworks.com> wrote in message 
<fbkicu$pg8$1@fred.mathworks.com>...
> Hi Stephen,
> 
> 
> 
> If you already have the desired coefficients, then you 
can use them to 
> directly construct an mfilt.iirinterp object.
> 
> 
> 
> For example, if you know your filter's coefficients are
> 
> 
> 
> [0.6 0.5] for the first phase in the first stage, 0.7 for 
the second phase 
> in the first stage and 0.8 for the third phase in the 
first stage;
> 
> 
> 
> as well as
> 
> 
> 
> 0.5 for the first phase in the second stage and 0.4 for 
the second phase in 
> the second stage.
> 
> 
> 
> You can just construct the filter as
> 
> 
> 
> Hm = mfilt.iirinterp({[0.6 0.5] 0.7 0.8},{0.5 0.4})
> 
> 
> 
> and you'll get
> 
> 
> 
> Hm =
> 
> 
> 
>         FilterStructure: 'IIR Polyphase Interpolator'
> 
>               Polyphase:   Phase1: Section1: [0.6 0.5]
> 
>                                               Section2: 
0.7
> 
>                                               Section3: 
0.8
> 
>                                  Phase2: Section1: 0.5
> 
>                                               Section2: 
0.4
> 
>     InterpolationFactor: 2
> 
>        PersistentMemory: false
> 
> 
> 
> The documentation and m-file help example focus on a 
design approach when 
> the coefficients are not known. I have submitted a 
documentation enhancement 
> request to explain this better. Another good reference 
regarding the design 
> of a quasi linear phase IIR halfband filter can be found 
in the following 
> demo:
> 
> 
> 
> http://www.mathworks.com/products/filterdesign/demos.html?
file=/products/demos/shipping/filterdesign/iirallpassdemo.ht
ml#16
> 
> 
> 
> HTH,
> 
> 
> 
> Honglei
> 
> 
> 
> 
> 
> "Stephen Burgess" <Stephen.Burgess@edu.fh-kaernten.ac.at> 
wrote in message 
> news:fbh4sj$1a4$1@fred.mathworks.com...
> > How do I specify a quassi linear phase iir halfband 
filter
> > using the mfilt.iirinterp( ) function, given a set of
> > coefficients.
> >
> > The available documention/examples in the help was 
rather
> > vague and incomplete.
> >
> > Could anyone provide a simple example?
> >
> > Stephen 
> 
>