1、fs=15000;T= 1/fs; rp=1;rs=40;wp1=0.11*pi;wp2=0.81*pi;ws1=0.31*pi;ws2=0.61*pi;%數(shù)字帶阻濾波器技術(shù)指標(biāo)wc1=(2/T)*tan(wp1/2);%頻率預(yù)畸變wc2=(2/T)*tan(wp2/2);wr1=(2/T)*tan(ws1/2);wr2=(2/T)*tan(ws2/2); w0=sqrt(wc1*wc2);B=wc2-wc1;wp=1;%歸一化通帶截止頻率ws=wp*(wr1*B) / (w02-wr12)歸一化阻帶截止頻率N,wc=buttord(wp,ws,rp,rs,s)%3dB 設(shè) 計(jì) 模 擬 低 通

2、 濾 波 器 將零極點(diǎn)形式轉(zhuǎn)換為傳輸函數(shù)形式M,N=lp2bs(Md,Nd,w0,B)%對(duì)低通濾波器進(jìn)行頻率變換，轉(zhuǎn)換為帶阻濾波器h,w=freqs(M,N);%模擬帶阻濾波器的幅頻響應(yīng)plot(w/(2*pi),abs(h);grid;xlabel(頻率 Hz);ylabel(幅度);title(模擬帶阻濾波器); b,a=bilinear(M,N,15000)%對(duì)模擬濾波器雙線性變換figure(1);freqz(b,a);H,W=freqz(b,a);%繪出頻率響應(yīng)；axis(0,1,-100,20);figure(2); plot(W*fs/(2*pi),abs(H);grid on;

3、 xlabel(頻率/Hz);ylabel(幅值);n=0:199;t=n/fs; x=sin(2*pi*400*t)+3*sin(2*pi*3000*t)+2*sin(2*pi*5000*t); figure(3);subplot(311);plot(t,x);axis(0,0.01,-5,5); title(輸入信號(hào));grid on;y=filter(b,a,x);subplot(312);stem(y,.);title(輸出序列);grid on;ya=y*sinc(fs*(ones(length(n),1)*t-(n/fs)*ones(1,length(t);subplot(313)

4、;plot(t,ya);axis(0,0.01,-3,3);title(輸出波形);grid on; t=(0:100)/fs;figure(4) fs=1.5*10000;n=(0:100)/fs; f=sin(2*pi*400*t)+3*sin(2*pi*3000*t)+2*sin(2*pi*5000*t); y=fftfilt(b,x);H1,f1=freqz(f,1);H2,f2=freqz(y,1); f1=f1/pi*fs/2; f2=f2/pi*fs/2;););e)d sue于ut ei rnMatlabg0g ea-50dM (-10000. 01 . 02 . 03 . 0

5、4 . 05 . 06 . 07 . 08 .1 9Normalr iazde/ dsae20200400600800s-amrlqeu-h-P0000. 01 .02 . 03. 04 . 05. 06 . 07 .08 .19Normalr ia zd e/dsa Fmrpelqeu1.41.210.8值幅0.60.40.20010002000300040005000600070008000頻率/Hz輸入信號(hào)50-500.0010.0020.0030.0040.0050.0060.0070.008輸出序列0.0120-2020406080100輸出波形12014016018020020-220015010000.0010.0020.0030.0040.0050.0060.0070.0080.0090.01輸入信號(hào)的頻譜500010002000300040005000600070008000輸出信號(hào)的頻譜3020100010002000300040005000600070008000N =4wc =1.7947b =0.01860.0186a =1.00000.0762-0.