u_buttap.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 [b,a] = u_buttap(N,Omegac);
% Unnormalized Butterworth Analog Lowpass Filter Prototype
% --------------------------------------------------------
% [b,a] = u_buttap(N,Omegac);
%      b = numerator polynomial coefficients of Ha(s)
%      a = denominator polynomial coefficients of Ha(s)
%      N = Order of the Butterworth Filter
% Omegac = Cutoff frequency in radians/sec
%
[z,p,k] = buttap(N);
      p = p*Omegac;
      k = k*Omegac^N;
      B = real(poly(z));
      b0 = k;
      b = k*B;
      a = real(poly(p));