1、习题一 绘制典型信号及其频谱图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(|F(omega)| in dB);figure;plot(w,angle
2、(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。上述代码(E=1;a=1)的图形如下所示:现改变参数再绘制图形:E=1;a=2;图形如下所示:E=2;a=1;图形如下所示:E=2;a=2;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()|-、|F()| in dB-在=0处的峰值越小,()-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
3、码如下:closeall;E=1;tau=1;t=-4:0.1:4;w=-30:0.1:30;f=E*(t-tau/2&ttau/2)+0*(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)|);figure;plot(w,20*log10(abs(F);xlabel(omega);ylabel(|F(omega)| in dB);figure;plot(w,angle(F);xlabel(omega);yla
4、bel(phi(omega);图形如下所示: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|t=-tau/2);Sa=sin(w*tau/2)./(w*tau/2);F=E*tau/2*Sa./(1-(w*tau/2/pi).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)| in dB);figure;plot(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)+0*(t=tau/2|t三角脉冲升余弦脉冲。