dir2fs.m

matlab写的数字信号处理源代码,里面包括最基本的fft计算

function [C,B,A] = dir2fs(h)
% Direct form to Frequency Sampling form conversion
% -------------------------------------------------
% [C,B,A] = dir2fs(h)
% C = Row vector containing gains for parallel sections
% B = Matrix containing numerator coefficients arranged in rows
% A = Matrix containing denominator coefficients arranged in rows
% h = impulse response vector of an FIR filter
%
M = length(h);
H = fft(h,M);
magH = abs(H); phaH = angle(H)';
% check even or odd M
if (M == 2*floor(M/2))
      L = M/2-1;   % M is even
     A1 = [1,-1,0;1,1,0];
     C1 = [real(H(1)),real(H(L+2))];
else
      L = (M-1)/2; % M is odd
     A1 = [1,-1,0];
     C1 = [real(H(1))];
end
k = [1:L]';
% initialize B and A arrays
B = zeros(L,2); A = ones(L,3);
% compute denominator coefficients
A(1:L,2) = -2*cos(2*pi*k/M); A = [A;A1];
% compute numerator coefficients
B(1:L,1) = cos(phaH(2:L+1));
B(1:L,2) = -cos(phaH(2:L+1)-(2*pi*k/M));
% compute gain coefficients
C = [2*magH(2:L+1),C1]';