数字滤波器程序问题，麻烦大家帮看看

jumboee

clear all
0 r- b" i% @! A%-------------------------------------------------------------
N=500;
4 l* p" r4 x% qp=0.05;
7 o" H# w1 B: e! I0 ]f=1/50;
n=1:N;
u=rand(1,N);
1 b1 ]" R$ o4 m4 Y0 u, k" U8 }s=sin(2*pi*f*0:N-1);
x=u(1:N)+s;
8 E0 P7 O! ^, A+ {, hsubplot(311)
plot(x(1:500));grid on;
ylabel('x(n)')
0 e$ [) Z% {" [/ k2 a( _" |1 P%---------------------------------------------------------------
1 J. b$ `3 z5 G! W  zfp=200;
fs=400;Fs=1200;
rp=3;  %通带衰减不大于3dB
- v9 ]2 Q  ?9 ]/ H& L% L( krs=35;  %阻带衰减不大于35dB
- |: ]$ F9 _8 Zwp=2*fp/Fs;
3 S2 I/ r6 z9 p3 D) gws=2*fs/Fs;
2 d% f: `  j; z( d* S" U+ _/ Zsyms a w real
[nz,wn]=buttord(wp,ws,rp,rs);
- E" S+ T4 V. c- g5 }# j6 h: V2 D- ^[bz,az]=butter(nz,wp,'low');
# I4 G( r: P1 Z' Z. |* a2 u[h,w]=freqz(bz,az,1024,Fs);
ih=ifourier(h);
subplot(312)
) q' T# h) A: \plot(x,h);grid;
/ v8 ]' k5 y3 w5 n" Wylabel('Low-pass DF')
1 ~+ U2 |$ p8 e# t$ K%--------------------------------------------------------
( O8 d5 d' H3 }" E6 H7 Gy=fftfilt(h,x);
subplot(313)
plot(y);
# y0 ^) a0 _* m. t. S) {, T' L
; T1 v. |- k7 G1 C画出的图不对，好像是逆傅里叶变换用的不太对似的。