closeall;fs=1000;t=0:1/fs:1;x=0.99*sin(2*pi*t);plot(t,x);holdon;M=8;delta=2/M;y_level=floor(abs(x/delta));signal=sign(x);fork=1:1000;实训二信源编码和信道编码一、实验内容1、对抽样信号进行均匀量化，改变量化级数和信号大小，根据MATLAB仿真获得量化误差和量化信噪比。2、对抽样信号进行A律压缩、均匀量化，改变量化级数和信号大小，根据MATLAB仿真获得量化误差和量化信噪比。3、限失真信源编码：米用A律13折线编码二、程序和仿真图1.fori=0:7;ifx(1,k)>=-1+i*delta&x(1,k)<=-1+(i+1)*delta;Q=signal.*(y_level*delta+delta/2);end;end;end;plot(t,Q,'r');gridon;title('原信号与均匀量化信号');2.closeall;fs=32;t=0:1/fs:1;x=sin(2*pi*t);subplot(2,1,1);plot(t,x);holdon;stem(t,x,'filled','r');title('采样样值和8级均匀量化后的样值');gridon;M=8;deta=2/M;y_level=fix(abs(x/deta));signal=sign(x);Q=signal.*(y_level*deta+deta/2);Q_error=x-Q;S=mean(x.A2);N=mean(Q_error42);stem(t,Q,'filled','b');legend('输入信号','采样量值','量化后量值');subplot(2,1,2);stem(t,Q_error,'filled','r');title('量化误差图');gridon;“采样样值和呂级均匀量化后的样值2iiiiii~~I-——输入需Iiiiiiiii_00_10.20_30.40_50.60.70.80.91量化i吴差團133.clearall;fs=2000;t=0:1/fs:1;x=sin(2*pi*t);c=[00000000];fork=2:1:8;[a,b,c(k)]=PCM(x,k);end;n=2:1:8;plot(n,c(2:8),'b');title('均匀量化信噪比编码位数变化');xlabel('编码位数');ylabel('量化信噪比');gridon;holdon;SNR_T=n*6.02+1.76;n=2:1:8;plot(n,SNR_T,'r-o');legend('仿真值','理论值');均匀量化信噪比编码位数变化——仿真值A理论值456编码位数4.clearall;fs=2000;t=0:1/fs:1;x=sin(2*pi*t);M=0:5:50;c=[0000000000];fork=1:1:11;y=x/(10"M(k)/20));[a,b,c(k)]=PCM(y,8);end;plot(M,c);c=[0000000000];fork=1:1:11;y=x/(10A(M(k)/20));[a,b,c(k)]=PCM(y,12);end;holdon;plot(M,c,'-ro');title('量化信噪比随信号衰减的变化情况');xlabel('信号衰减(dB)');ylabel('量化信噪比(dB)');gridon;legend('均匀量化(8bits)','均匀量化(12bits)');5.clearall;A=87.6;tc=1/32000;t=0:tc:1;%%x=0.99*sin(2*pi*t);V=max(x);figure(1);subplot(3,1,1);plot(t,x);title('压缩前信号');holdon;gridon;%%x1=compand(x,A,V,'A/compressor');plot(t,x1,'r');title('A律压缩后信号');legend('压缩前信号','A律压缩后信号');%%f=1/32;t1=0:f:1;y1=downsample(x1,f/tc);subplot(3,1,2);OooO643OO6.stem(t1,y1,'b');title('A律压缩信号样值');holdon;gridon;%%[index,y2]=quantiz(y1,-6/8:2/8:6/8,-7/8:2/8:7/8);stem(t1,y2,'r','filled');title('A律压缩信号样值和8级均匀量化的样值');xlabel('t(s)');ylabel('幅值');legend('A律压缩信号样值','8级均匀量化样值');%%%%%%%%%subplot(3,1,3);stem(t1,y2-y1,'r','filled');xlabel('t(s)');title('量化误差');gridon;closeall;A=1;L1=[8,12];tc=1/200000;t=0:tc:1;x0=sin(2*pi*t);r=0:5:50;sqnr=zeros(1,length(r));forj=1:2L=L1(j);fori=1:length(r)A1=1/(10"r(i)/20));x=A1*x0;f=1/2000;t1=0:f:1;y1=downsample(x,f/tc);M=2AL;[index,y2]=quantiz(y1,-(M-1)/M:2/M:(M-1)/M,-1:2/M:1);sqnr(i)=10*log10(mean(y1.A2)./mean((y1-y2).A2));endifj==1plot(r,sqnr,'ro--');holdon;elseplot(r,sqnr,'ro-');title('量化信噪比随信号衰减变化的曲线');holdon;endend%%%%%%%%snr1=6.02*8+1.76;snr2=6.02*12+1.76;fori=1:11s1(i)=snr1-5*(i-1);endfori=1:11s2(i)=snr2-5*(i-1);endplot(r,s1,'k:');gridon;holdon;plot(r,s2,'k--');gridon;%%%%%%%%%%%%L=L1(1);A1=87.6;fori=1:length(r)x=x0/(10A(r(i)/20));xmax=max(abs(x));x1=zeros(1,200001);forj=1:200001ifabs(x(j))<=1/A1x1(j)=A1*x(j)/(1+log(A1));elsex1(j)=sign(x(j))*(1+log(A1*abs(x(j))))/(1+log(A1));endendf=1/2000;t1=0:f:1;y1=downsample(x1,f/tc);yy=downsample(x,f/tc);M=2AL;[index,y2]=quantiz(y1,-(M-1)/M:2/M:(M-1)/M,-1:2/M:1);x2=zeros(1,2001);fork=1:2001ifabs(y2(k))<=1/(1+log(A1))x2(k)=y2(k)*(1+log(A1))/A1;elsex2(k)=sign(y2(k))/A1*exp(abs(y2(k))*(1+log(A1))-1);endendsqnr(i)=10*log10(mean(yy.A2)./mean((yy-x2).A2));endplot(r,sqnr,'b*-');gridon;title('量化信噪比随信号衰减变化的曲线');xlabel('信号的衰减dB');ylabel(量化信噪比');axis([0,50,0,80]);legend('均匀量化(8bits)','均匀量化(12bits)','均匀量化理论值(8bits)','均匀量化理论值(8bits)','A律压缩量化(8bits)');量化信噪比随信号衰减变化的曲线OOOOOOOOO87654321I-—O—均匀里化但bits）均匀量化门的⑸均匀量化理论值困血）均匀量化理论值（盹曲）T^A律压缩量化（曲⑸IIIIIII-IIIIlli■jjn-.IIIiiiiW"IIIIIIII1015202530354046信号的衰减归
