习题一绘制典型信号及其频谱图

1、标准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:close all ;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);XIabe1('t' );ylabel('f(t)');文案figure;Plot(W,abs(F);XIabe1('omega');ylabel('F(omega)');figure;PlOt(W,20*log10(abs(F);XIabe1('omega');ylab

2、el( 'F(omega) in dB');figure;PlOt(W,angle(F);XIabe1('omega' );ylabel('phi(omega)');请更改参数，调试此程序, 其频谱的影响。绘制单边指数信号的波形图和频谱图。观察参数a对信波形及上述代码(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( )|- 3、F( )| in dB- 在 =O处的峰

3、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。 矩形脉冲代码如下：close all E=1;tau=1; t=-4:0.1:4;w=-30:0.1:30;f=E*(t>-tau2&t<tau 2)+0*(t<=-tau2&t>=tau/2);F=(2*E.w).*si n(w*tau2);plot(t,f);Xlabe1('t')ylabel('f(t)');figure;Plot(W,abs(F);Xlab

4、e1('omega' );ylabel( 'F(omega)');figure;plot(w,20*log10(abs(F);xlabel(figure;plot(w,a ngle(F);xlabel('omega''omega' );ylabel( 'F(omega);ylabel( 'phi(omega)');in dB');图形如下所示:0.90.80.70.G050.4 3Q.2D.12101232阳>40-cp 匸二34-O20G.5-20 -10O102030-30 升余弦脉冲 代

5、码如下： clear all ;E=1;tau=1;t=-3:0.1:3;w=-30:0.1:30;f=(E2*(1+cos(2*pi*ttau).*(t>-tau2&t<tau 2)+0*(t>=tau2t<=-tau2)；Sa=Si n(w*tau2).(w*tau2);plot(t,f);xlabel('t' );ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('F(omega)'F=E*tau2*Sa.(1-(w*tau2

6、pi).2);figure;);Plot(W,20*log10(abs(F);Xlabe1( figure;'omega' );ylabel( 'F(omega) in dB');plot(w,a ngle(F);xlabel('omega' );ylabel('phi(omega)');图形如下所示: 三角脉冲代码如下:close allE=1;tau=1;t=-3:0.1:3;w=-30:0.1:30;f=E*(1-2*abs(t)tau).*(t<tau2&t>-tau 2)+0*(t>=tau2t

7、<=-tau2);Sa=Si n(w*tau4).(w*tau4);plot(t,f);xlabel('t' );ylabel('f(t)');figure;plot(w,abs(F);xlabel('omega');ylabel('F(omega)'F=E*tau2*Sa.2;);figure;PIot(W,20*log10(abs(F);xlabel('omega' );ylabel( 'F(omega)in dB');figure;plot(w,a ngle(F);xlabel('omega' );ylabel('phi(omega)');图形绘制如下: