华工DSP实验考试报告.docx

DSP考试实验报告 姓名学号专业班级电信提交日期2014年12月18日 一、频分复用1 选择3个不用频段的信号，画出其频谱%1.150Hz,300Hz450Hz t=0:0.001:1;x1=cos(2*pi*150*t);x2=cos(2*pi*300*t);x3=cos(2*pi*450*t);y1=fft(x1,256);y2=fft(x2,256);y3=fft(x3,256);f=1000*(0:128)/256;figure(1);subplot(3,1,1);plot(f,abs(y1(1:129);xlabel(频率);ylabel(幅度);subplot(3,1,2);plot(f,abs(y2(1:129);xlabel(频率);ylabel(幅度);subplot(3,1,3);plot(f,abs(y3(1:129);2 将三路信号合成一路信号，画出合成信号的时域和频域波形%2.3路信号合成1路信号figure(2);x=x1+x2+x3;stem(t,x);subplot(2,1,1);stem(t,x);plot(x(1:128);xlabel(t);ylabel(y);title(时域);subplot(2,1,2);y=fft(x,256);plot(f,abs(y(1:129);xlabel(频率);ylabel(幅度);title(频域);3将合成信号分别通过设计好的数字滤波器，分离出原来的三路信号，分析得到的三路信号的时域波形和频谱，与原始的三路信号进行比较说明频分复用的特点4将所用滤波器的频谱画出来%低通t=0:0.001:1;x1=cos(2*pi*150*t);x2=cos(2*pi*300*t);x3=cos(2*pi*450*t);x=x1+x2+x3;y1=fft(x,256);fp=200;fs=1200;ft=4000;rp=1;rs=40; T=1/ft; wp=2*pi*fp/ft; ws=2*pi*fs/ft; omegap=(2/T)*tan(wp/2); omegas=(2/T)*tan(ws/2); N,wn=buttord(omegap,omegas,rp,rs,s); num,den=butter(N,wn,low,s); numz,denz=bilinear(num,den,ft); figure(3) freqz(numz,denz) y=filter(numz,denz,x);y2=fft(y,256);f=1000*(0:128)/256;subplot(4,1,3);plot(f,abs(y1(1:129);xlabel(频率);ylabel(幅度);title(原始信号频域);subplot(4,1,4);plot(f,abs(y2(1:129);xlabel(频率);ylabel(幅度);title(滤波后频域);%带通 t=0:0.001:1;x1=cos(2*pi*150*t);x2=cos(2*pi*300*t);x3=cos(2*pi*450*t);x=x1+x2+x3;y1=fft(x,256);fp1=900;fp2=1300;fs1=600;fs2=1500;ft=4000;rp=1;rs=40; T=1/ft; wp=2*pi*fp1 fp2/ft; ws=2*pi*fs1 fs2/ft; omegap=(2/T)*tan(wp/2); omegas=(2/T)*tan(ws/2); N,wn=buttord(omegap,omegas,rp,rs,s); num,den=butter(N,wn,bandpass,s); numz,denz=bilinear(num,den,ft); figure(5) freqz(numz,denz)y=filter(numz,denz,x);y2=fft(y,256);f=1000*(0:128)/256;subplot(4,1,3);plot(f,abs(y1(1:129);xlabel(频率);ylabel(幅度);title(原始信号频域);subplot(4,1,4);plot(f,abs(y2(1:129);xlabel(频率);ylabel(幅度);title(滤波后频域);%高通t=0:0.001:1;x1=cos(2*pi*150*t);x2=cos(2*pi*300*t);x3=cos(2*pi*450*t);x=x1+x2+x3;y1=fft(x,256);fp=1400;fs=1500;ft=4000;rp=1;rs=40; T=1/ft; wp=2*pi*fp/ft; ws=2*pi*fs/ft; omegap=(2/T)*tan(wp/2); omegas=(2/T)*tan(ws/2); N,wn=buttord(omegap,omegas,rp,rs,s); num,den=butter(N,wn,high,s); numz,denz=bilinear(num,den,ft); figure(4) freqz(numz,denz) y=filter(numz,denz,x);y2=fft(y,256);f=1000*(0:128)/256;subplot(4,1,3);plot(f,abs(y1(1:129);xlabel(频率);ylabel(幅度);title(原始信号频域);subplot(4,1,4);plot(f,abs(y2(1:129);xlabel(频率);ylabel(幅度);title(滤波后频域);频率复用系统的优点：信道复用率高，允许复用的路数多，同时它的分路也很方便。二、音频信号分析1读出所给音频信号，确定该音频信号的采样率=44100Hz和量化比特数=16.画出该音频信号的时域波形和频谱图2对该音频信号以间隔M=2进行采样，回放音频信号，感觉和原来有什么不同?N1=100000;N2=600000;x,fs,bits=wavread(C:UserslcDesktoplaughing.wav,N1,N2);wavwrite(x,44100,C:UserslcDesktoplaughingnew.wav);Nx=N1:N2;figure;subplot(2,1,1);plot(Nx,x(:,1);title(C 1);subplot(2,1,2);plot(Nx,x(:,2);title(C 2);figure;subplot(2,1,1);X1=fft(x(:,1);plot(Nx,fftshift(X1);title(C 1);subplot(2,1,2);X2=fft(x(:,2);plot(Nx,fftshift(X2);title(C 2);x1c=x(1:2:length(x),1);x2c=x(1:2:length(x),2);for i=1:length(x)/2xnew(i,1)=x1c(i);xnew(i,2)=x2c(i);endwavwrite(xnew,40000,C:UserslcDesktoplaughingnewoo.wav);采样后的音频信号比原来的速度更快，而且音调更尖锐。3你想怎么解决？为什么？在采样后的每个点中间插入相邻两点的平均值以恢复原信号。4画出解决前后音频信号的波形及频谱for i=1:2:length(x)-10xori(i,1)=x1c (i+1)/2);xori(i,2)=x2c (i+1)/2);xori(i+1,1)=0.5*(x1c (i+1)/2)+x1c (i+3)/2);xori(i+1,2)=0.5*(x2c (i+1)/2)+x2c (i+3)/2);endwavwrite(xori,40000,laughing_ori.wav);%4figure;subplot(3,1,1);plot(1:length(x)-1,x(1:length(x)-1,:);title(origin);subplot(3,1,2);plot(1:2:length(x)-1,xnew);title(Down Sampling);subplot(3,1,3);plot(1:length(x)-9,xori);title(Regain);figure;subplot(3,1,1);plot(1:length(x)-1,abs(fftshift(fft(x(1:length(x)-1,:);title(origi