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Topic: FIR Filter
Replies: 9   Last Post: Sep 20, 2009 1:25 PM

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Wayne King

Posts: 2,961
Registered: 4/1/09
Re: FIR Filter
Posted: Sep 19, 2009 9:23 AM
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"alfredo " <luka_ice@hotmail.com> wrote in message <h92ku4$2o2$1@fred.mathworks.com>...
> Rune Allnor <allnor@tele.ntnu.no> wrote in message <6d6346f2-e093-4f73-a99b-156b9b675eb0@y42g2000yqb.googlegroups.com>...
> > On 13 Sep, 12:10, "alfredo " <luka_...@hotmail.com> wrote:
> > > I have some problems with FIR filter,someone can help me?
> > >
> > > I write my pseudo code:
> > >
> > > clear all;
> > > Asim=[17, 18]; ?%Definisce le ampiezze
> > > Tsim=[22.5, 33.48]; ?%Definisce i periodi
> > > fase=[1.1, 2.2]; ?%Definisce le fasi
> > > p=1:2048;
> > > value=0; ?%Oscilla attorno la linea dello zero se value=0
> > > Coseno1=0;
> > > Coseno2=0;
> > > Coseno1=Coseno1+Asim(1)*cos(2*pi*1/Tsim(1)*p+fase(1))';
> > > Coseno2=Coseno2+Asim(2)*cos(2*pi*1/Tsim(2)*p+fase(2))';
> > >
> > > serie12=Coseno1+Coseno2;
> > > step =0.01;
> > >
> > > serie= serie12;
> > > step=0.01;
> > > Tmin=8;
> > > Tmax=120;
> > > A=length(serie);
> > >
> > > Y=fourier(serie',Tmax,Tmin,step); ? ? ? ? ? ?%fourier trasform
> > >
> > > Ok , now how can I implement a high pass filter FIR, for cut off ?the frequency 1/ 33.48 ?

> >
> > What has all this to do with designing filters?
> >
> > Rune

>
>
>
> I try with this:
>
> d = fdesign.highpass('Fst,Fp,Ast,Ap',0.03,0.043,60,0.5,10000) ;
> Hd = design(d,'FIR');
> smoothed_data = filter(Hd,Y);
>
> but I have some problems, I thik because I have R2007b version...


Hi Alfredo, the filter specification objects such as fdesign.highpass were introduced in the Signal Processing Toolbox in R2009a, they are part of the Filter Design Toolbox prior to that.
In R2007b, you have a number of non-object-oriented FIR design routines available in the Signal Processing Toolbox. Take a look at firpm() for an equiripple design, fir1() for a window method FIR design, fir2() uses frequency sampling, and firls() for least-squares error minimization as examples. Post back if you have difficulty, I'm not sure you really want the filter design you have above in fdesign.highpass (or I would have given you a comparable example) because you are basically just passing everthing. Your stopband frequency is only 0.03 Hz? (you have a sampling frequency of 10 kHz specified), your passband starts at 0.043 Hz...

Hope that helps,
wayne



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