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1、步骤一中的程序和出来的图采样率为1Hz，高通滤波器f=1hz;fp=0.3hz;fs=0.2;Rp=ap=0.8db;Rs=as=20db>>fp=0.3;fs=0.2;Rp=0.8;Rs=20;>>[n,Wn]=cheb1ord(0.3,0.2,0.8,20);>>[b,a]=cheby1(n,0.8,Wn,'high');>>freqz(b,a,512,1)>>subplot(2,1,1);title('幅度谱')>>subplot(2,1,2);title('相位谱')根据程序算出n=4a=1.0000-1.14461.083
2、5-0.28620.1599b=0.2094-0.83771.2566-0.83770.2094数字高通滤波器的传递函数为H(z)=(0.2094-0.8377z-1+1.2566z-2-0.8377z-3+0.2094z-4)/(1-1.1446z-1+1.0835z-2-0.2862z-3+0.1599z-4)步骤二中的程序和出来的图采样频率为1hz，低通滤波器f=1hz;fp=0.2hz;fs=0.3hz;ap=1db;as=25db;>>fp=0.2;fs=0.3;Rp=1;Rs=25;>>[n,Wn]=cheb1ord(0
3、.2,0.3,1,25);>>[b,a]=cheby1(n,1,Wn);>>freqz(b,a,512,1)>>subplot(2,1,1);title('幅度谱')>>subplot(2,1,2);title('相位谱')根据程序算出n=5a=1.0000-3.96346.6990-5.98152.8111-0.5558b=0.00030.00150.00290.00290.00150.0003数字滤波器的传递函数为H(z)=(0.0003+0.0015z-1+0.0029z-2+0.0029z-3+0.0015z-4+0.000
4、3z-5)/(1-3.9634z-1+6.6990z-2-5.9815z-3+2.8111z-4-0.5558z-5)步骤二中的程序和出来的图butterword带通数字滤波器T=10us;fp1=20khz;fp2=30khz;fs1=15khz;fs2=35khz;ap=1db;as=40db;所以有:Wp1=fp1*T=0.2；Wp2=fp2*T=0.3；Ws1=fs1*T=0.15；Ws2=fs2*T=0.35；fp=[0.2,0.3];fs=[0.15,0.35]>>fp=[0.2,0.3];fs=[0.15,0.35];
5、>>[n,Wn]=buttord(fp,fs,1,40);>>[b,a]=butter(n,Wn);>>freqz(b,a,512,1)>>subplot(2,1,1);title('幅度谱')>>subplot(2,1,2);title('相位谱')根据程序算出：n=9a=1.0e+003*[0.0010-0.01140.0653-0.24510.6745-1.44112.4723-3.47724.0607-3.96463.2432-2.21811.2595-0.58640.2192-0.06360.0135-0.00190.00
6、01]b=1.0e-005*[0.00600-0.053700.21470-0.501000.75150-0.751500.50100-0.214700.05370-0.0060]
