freqz的逆變換invfreqz

                                  作者  makethyme

%invfreqz_learn.m
%invfreqz()爲freqz的逆變換
b=fir1(48,0.4);
[h,w]=freqz(b,1,512);
b1=invfreqz(h,w,48,1);
figure;
plot(b,'r'),hold on;
plot(b1,'g'),hold off;