noise reduction in fir filter

i want to design a bandpass fir filter with Bartlett or hamming window,and want to reduce the pass and stop band ripple.is there any math function to describe it. plz suggest.

Answer 1

[Wayne King]

Hi Debalina, If you want to use the window method for a bandpass filter, you can do the following (of course you need to modify the specifications to match your needs)

    % I'll assume a 10-kHz sampling frequency and pass 1000-1500 Hz
    d = fdesign.bandpass('N,Fc1,Fc2',10,1000,1500,10000);
    % Use a Hamming window
    Hd = window(d,'window',@hamming);
    fvtool(Hd);

However, if you really want to control the passband and stopband ripple, then I think a different FIR design is warranted, like a constrained equiripple design. See firceqrip() for example.

Answer 2

[debalina ghosh]

sir, i have tried following your specification firceqrip(). below is my code :

         clear all

Fs = 100000;

Fn = Fs/2;

N = 200;

B = 16;

fc1 = 4911/Fn; %lower cutoff
fc2 = 5645/Fn;

Fc = [ fc1 fc2];

w = bartlett(N+1);

w = w/max(w);

w = round(w.*((2^(B-1))-1));
b = firceqrip(N,Fc,'bandpass',w);

Hd = dfilt.dffir(b);

    Hd.arithmetic = 'fixed'; % Requires the Fixed-Point Toolbox

    coewrite(Hd,16,'nrduce_bfcoefile');
Error in ==> firceqrip at 394
    rs = [fo*(0:n1-1)/n1, fo, fo+(1-fo)*(1:n2)/n2]';

Error in ==> nooiserbar at 12
b = firceqrip(N,Fc,'bandpass',w);

please help

[Walter Roberson]

You seem to have trimmed out the basic message about what error it thinks is occurring ?

Answer 3

[debalina ghosh]

sir,

my error is Error in ==> firceqrip at 394 rs = [fo*(0:n1-1)/n1, fo, fo+(1-fo)*(1:n2)/n2]'; Error in ==> nooiserbar at 12 b = firceqrip(N,Fc,'bandpass',w); sir, i could not understood how would i rectify it.please help

[Walter Roberson]

MATLAB never simply says that there is an error: it says what kind of error there is. For example, it might be displaying an error "vertcat error"