c4_5_1.m

dsp入门与实践一书的源代码

function [des,wt] = taperedresp(order, ff, grid, wtx, aa)
	nbands = length(ff)/2;					
	des=grid;
	wt=grid;
	for i=1:nbands
		k = find(grid >= ff(2*i-1) & grid <= ff(2*i));
		npoints = length(k); 
		t = 0:npoints-1;
		des(k) = linspace(aa(2*i-1), aa(2*i), npoints);
			if i = = 1
				wt(k) = wtx(i) * (1.5 + cos((t)*pi/(npoints-1)));
				elseif i = = nbands
					wt(k) = wtx(i) * (1.5 + cos(pi+(t)*pi/(npoints-1)));
				else
					wt(k) = wtx(i) * (1.5 - cos((t)*2*pi/(npoints-1)));
				end
			end
 [b,err,res]=gremez(53, [0 0.3 0.33 0.77 0.8 1],{'taperedresp',[0 0 1 1 0 0]}, [2 2 1]);
 [H,W,S]=freqz(b,1,1024);
 S.plot = 'mag'; S.yunits = 'linear';
 freqzplot(H,W,S);