实验四连续系统的频域分析

1(1)方波的合成实验。用5项谐波合成一个频率为50Hz，幅值为3 的方波，写出MATLAB程序，给出实验的结果。clear all;fs=10000;t=0:1/fs:0.1;f0=50;sum=0;subplot(211)for n=1:2:9;plot(t,3/pi*1/n*sin(2*pi*n*f0*t), k);hold on;endtitle( 信号叠加前)；subplot(212)for n=1:2:9;sum=sum+3/pi*1/n*sin(2*pi*n*f0*t);endplot(t,sum,k)；title( 信号叠加后)；0.50 -0.5 -100.010.020.030.040.050.060.070.080.090.110.50 -0.5-100.010.020.030.040.050.060.070.080.090.12(2)编写程序，画出信号f (t) = e-3代(t), f (t-4)以及信号f (t)e-j4的频谱图。r=0.02;t=-5:r:5;N=200;W=2*pi;k=-N:N;w=k*W/N;f1=1火exp(-3火t).*stepfun(t,0);F=r*f1*exp(-j*t*w);F1=abs(F);p1=angle(F);subplot(3,1,1);plot(t,f1);gridxlabel(t);ylabel(f(t);title(f(t);subplot(3,1,2);plot(w,F1);xlabel(w);grid;ylabel(F(jw);subplot(3,1,3);plot(w,p1*18 0/pi);grid;xlabel(w);ylabel( 相位(度) )；1M)0.50-5-4-3-2-1012345r=0.02;t=-5:r:5;N=200;W=2*pi;k=-N:N;w=k*W/N;f1=1*exp(-3*(t-1).*stepfun(t,0);F=r*f1*exp(-j*t*w);F1=abs(F);p1=angle(F);subplot(3,1,1);plot(t,f1);gridxlabel(t);ylabel(f(t);title(f(t-1);subplot(3,1,2);plot(w,F1);xlabel(w);grid;ylabel(F(jw)的模);subplot(3,1,3);plot(w,p1*180/pi);grid;xlabel(w);ylabel(相位(度);0 -50.5f(t-1)-4-3-2-1012345200-200-80-6-4-202461 WF 0频谱F1(jw)-11111111-40-30-20-10010203040R=0.02;t=-5:R:5;f=stepfun(t,-1)-stepfun(t,1);f1=f.*exp(-j*4*t);W1=2*pi*5;N=500;k=-N :N ;W=k*W1/N;F1=f1*exp(-j*t*W)*R;F1=real(F1);subplot(2,1,1);plot(W,F1);xlabel(W);ylabel(F1(W);title(频谱 F1(jw);