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fir2

PURPOSE ^

% error: b = fir2(n, f, m [, grid_n [, ramp_n]] [, window])

SYNOPSIS ^

function b = fir2(n, f, m, grid_n, ramp_n, window)

DESCRIPTION ^

% error: b = fir2(n, f, m [, grid_n [, ramp_n]] [, window])
%
% Produce an FIR filter of order n with arbitrary frequency response, 
% returning the n+1 filter coefficients in b.  
%
% n: order of the filter (1 less than the length of the filter)
% f: frequency at band edges
%    f is a vector of nondecreasing elements in [0,1]
%    the first element must be 0 and the last element must be 1
%    if elements are identical, it indicates a jump in freq. response
% m: magnitude at band edges
%    m is a vector of length(f)
% grid_n: length of ideal frequency response function
%    defaults to 512, should be a power of 2 bigger than n
% ramp_n: transition width for jumps in filter response
%    defaults to grid_n/20; a wider ramp gives wider transitions
%    but has better stopband characteristics.
% window: smoothing window
%    defaults to hamming(n+1) row vector
%    returned filter is the same shape as the smoothing window
%
% To apply the filter, use the return vector b:
%       y=filter(b,1,x);
% Note that plot(f,m) shows target response.
%
% Example:
%   f=[0, 0.3, 0.3, 0.6, 0.6, 1]; m=[0, 0, 1, 1/2, 0, 0];
%   [h, w] = freqz(fir2(100,f,m));
%   plot(f,m,';target response;',w/pi,abs(h),';filter response;');

CROSS-REFERENCE INFORMATION ^

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