FIR Filter Design（有限冲击响应滤波器设计）

				% ddiff.m - ideal lowpass differentiator FIR filter				%				% h = ddiff(wc, N) = row vector				%				% N = 2M+1 = filter length (odd)				% wc in rads/sample								function h = ddiff(wc, N)								M = (N-1)/2;								for k = -M:M,				  if k == 0,				    h(k+M+1) = 0;				  else				    h(k+M+1) = wc * cos(wc * k) / (pi * k) - sin(wc * k) / (pi * k^2);				  end				end