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

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alfredo

Posts: 11
Registered: 5/27/09
Re: FIR Filter
Posted: Sep 20, 2009 12:38 PM
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"Wayne King" <wmkingty@gmail.com> wrote in message <h92lvl$866$1@fred.mathworks.com>...
> "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


thank you for this information, I try immediately these function but I can select if I want a high pass or a lowpass filter?
the freq 0,03 and 0.043 ara the inverse of the period of cicles 22.5 and 33.48 ( I want to cutoff the 33.48 period cycle ), I'm not sure of f sampling becouse I work with time series .

Alfredo



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