习题一 绘制典型信及其频谱图

1、习题一绘制典型信号及其频谱图(1)绘制单边指数信号及其频谱图的MATLAB程序如下：closeall;E=1;a=1;t=0:0.01:4;w=-30:0.01:30;f=E*exp(-a*t);F=E./(a+j*w);plot(t,f);xlabel('t');ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('|F(omega)|');figure;plot(w,20*log10(abs(F);xlabel('omega');ylabel(&

2、#39;|F(omega)|indB');figure;plot(w,angle(F);xlabel('omega');ylabel('phi(omega)');请更改参数，调试此程序，绘制单边指数信号的波形图和频谱图。观察参数a对信号波形及其频谱的影响。现改变参数再绘制图形：E=1;a=2;图形如下所示：图形如下所示：由图可知，a越大，单边指数信号的波形图f(t)-t下降越快，其频谱图|F(s)|-3、|F(s)|indB-3在3=0处的峰值越小，©(3)-3的初始近似水平段的值也越小。(2)绘制矩形脉冲信号、升余弦脉冲信号和三角脉冲信号的波

3、形图和频谱图，观察并对比各信号的频带宽度和旁瓣的大小。矩形脉冲代码如下：closeall;E=1;tau=1;t=-4:0.1:4;w=-30:0.1:30;f=E*(t>-tau/2&t<tau/2)+0*(t<=-tau/2&t>=tau/2);F=(2*E./w).*sin(w*tau/2);plot(t,f);xlabel('t');ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('|F(omega)|');fig

4、ure;plot(w,20*log10(abs(F);xlabel('omega');ylabel('|F(omega)|indB');figure;plot(w,angle(F);xlabel('omega');ylabel('phi(omega)');图形如下所示：18/16-101020升余弦脉冲代码如下：clearall;E=1;tau=1;t=-3:0.1:3;w=-30:0.1:30;f=(E/2*(1+cos(2*pi*t/tau).*(t>-tau/2&t<tau/2)+0*(t>=tau

5、/2|t<=-tau/2);Sa=sin(w*tau/2)./(w*tau/2);F=E*tau/2*Sa./(1-(w*tau/2/pi).A2);plot(t,f);xlabel('t');ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('|F(omega)|');figure;plot(w,20*log10(abs(F);xlabel('omega');ylabel('|F(omega)|indB');figure;p

6、lot(w,angle(F);xlabel('omega');ylabel('phi(omega)');图形如下所示：三角脉冲代码如下：closeall;E=1;tau=1;t=-3:0.1:3;w=-30:0.1:30;f=E*(1-2*abs(t)/tau).*(t<tau/2&t>-tau/2)+0*(t>=tau/2|t<=-tau/2);Sa=sin(w*tau/4)./(w*tau/4);F=E*tau/2*Sa/2;plot(t,f);xlabel('t');ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('|F(omega)|');figure;plot(w,20*log10(abs(F);xlabel('omega');ylabel('|F(omega)|indB');figure;plot(w,angle(F);xlabel('omega');ylabel('phi(omega)');图形绘制如下：0.8