Hello,
The following code fails completely. Instead of producing the requested filter it returns the filter coefficients as all zeros. Here's the code: % design narrowband filter f = [0.444 0.49 0.51 0.556 ]; a = [0 1 0]; dev = [0.0316 0.05 0.0316]; % estimate order using remezord [n,fo,ao,w] = remezord(f,a,dev) % get filter coefficients b = remez(n,fo,ao,w); % ERROR: the b vector is all zeros. % How is this possible? thanks 

strange result for filter design
Started by ●January 6, 2003
Reply by ●January 6, 200320030106
Moshe Malkin What is the order of the filter returned by remezord? Jeff Brower Signalogic > The following code fails completely. > Instead of producing the requested filter > it returns the filter coefficients as all zeros. > > Here's the code: > > % design narrowband filter > f = [0.444 0.49 0.51 0.556 ]; > a = [0 1 0]; > dev = [0.0316 0.05 0.0316]; > % estimate order using remezord > [n,fo,ao,w] = remezord(f,a,dev) > % get filter coefficients > b = remez(n,fo,ao,w); > > % ERROR: the b vector is all zeros. > % How is this possible? > thanks 
Reply by ●January 6, 200320030106
Moshe, what are you design specifications? I think you may have normalized incorrectly, or set up vector dev incorrectly. You might check that, for some stupid reason every filter design program in matlab is different! It annoys me that they did not standardized this aspect of Matlab, it has caused me much headache. Let me know, and I will see what I can do. The following is some sample code I programmed a while ago using the remez exchange algy. You might be able to apply this to help trouble shoot your problem Fs = 48e3 fp1 = 80 fs1 = 70 fp2 = 160 fs2 = 200 fp = [fp1/(Fs) fp2/(Fs)]; %Passband edge frequencies fs = [fs1/Fs fs2/Fs];%Stopband edge frequencies ws = 70; %Stopband attenuation wp = .02; %Passband attenuation %Application of the remez algorithm %Calculate ripple specs in decimal form, see page 725 of Ambardar handout %Eq. 20.9 and 20.10 epb = 10^(wp/20); esb = 10^ (ws/20); dp = (epb  1)/(epb + 1) ds = (1 + dp)*esb D = [ds dp ds]; %Deviation vector for remezord [N,fo,mo,w] = remezord( [fs(1) fp(1) fp(2) fs(2)], [0,1,0],D,1) N = 2*floor(N/2 + 1/2); %This assures that N is an even number hz = remez(N,fo,mo,w); Moshe Malkin <> wrote:Hello, The following code fails completely. Instead of producing the requested filter it returns the filter coefficients as all zeros. Here's the code: % design narrowband filter f = [0.444 0.49 0.51 0.556 ]; a = [0 1 0]; dev = [0.0316 0.05 0.0316]; % estimate order using remezord [n,fo,ao,w] = remezord(f,a,dev) % get filter coefficients b = remez(n,fo,ao,w); % ERROR: the b vector is all zeros. % How is this possible? thanks _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/matlab More DSPRelated Groups: http://www.dsprelated.com/groups.php3  
Reply by ●January 6, 200320030106
Hi, That appears to be a bug in remez. See http://www.mathworks.com/support/solutions/data/31015.shtml Navan  Moshe Malkin <> wrote: > Hello, > The following code fails completely. > Instead of producing the requested filter > it returns the filter coefficients as all zeros. > > Here's the code: > > % design narrowband filter > f = [0.444 0.49 0.51 0.556 ]; > a = [0 1 0]; > dev = [0.0316 0.05 0.0316]; > % estimate order using remezord > [n,fo,ao,w] = remezord(f,a,dev) > % get filter coefficients > b = remez(n,fo,ao,w); > > % ERROR: the b vector is all zeros. > % How is this possible? > thanks __________________________________________________ 

Reply by ●January 7, 200320030107
thats right. I'm using Matlab version 5.2 and the code runs absolutely
fine. the output of the code is attached. priyank  navaneetha krishnan <> wrote: > Hi, > > That appears to be a bug in remez. > > See > http://www.mathworks.com/support/solutions/data/31015.shtml > > Navan > >  Moshe Malkin <> wrote: > > Hello, > > > > > > The following code fails completely. > > Instead of producing the requested filter > > it returns the filter coefficients as all zeros. > > > > Here's the code: > > > > % design narrowband filter > > f = [0.444 0.49 0.51 0.556 ]; > > a = [0 1 0]; > > dev = [0.0316 0.05 0.0316]; > > % estimate order using remezord > > [n,fo,ao,w] = remezord(f,a,dev) > > % get filter coefficients > > b = remez(n,fo,ao,w); > > > > % ERROR: the b vector is all zeros. > > % How is this possible? > > > > > > thanks > __________________________________________________ __________________________________________________  
