習(xí)題一繪制典型信號(hào)及其頻譜圖

1、標(biāo)準(zhǔn)習(xí)題一繪制典型信號(hào)及其頻譜圖(1)繪制單邊指數(shù)信號(hào)及其頻譜圖的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)');請(qǐng)更改參數(shù)，調(diào)試此程序, 其頻譜的影響。繪制單邊指數(shù)信號(hào)的波形圖和頻譜圖。觀察參數(shù)a對(duì)信波形及上述代碼(E=1 ； a=1 )的圖形如下所示:現(xiàn)改變參數(shù)再繪制圖形: E=1;a=2;圖形如下所示： E=2;a=1;圖形如下所示: E=2;a=2;圖形如下所示:由圖可知，a越大，單邊指數(shù)信號(hào)的波形圖f(t)-t下降越快，其頻譜圖F( )|- 3、F( )| in dB- 在 =O處的峰

3、值越小， ( )- 的初始近似水平段的值也越小。(2)繪制矩形脈沖信號(hào)、升余弦脈沖信號(hào)和三角脈沖信號(hào)的波形圖和頻譜圖，觀察并對(duì)比 各信號(hào)的頻帶寬度和旁瓣的大小。 矩形脈沖代碼如下：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');圖形如下所示:0.90.80.70.G050.4 3Q.2D.12101232陽>40-cp 匸二34-O20G.5-20 -10O102030-30 升余弦脈沖 代

5、碼如下： 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)');圖形如下所示: 三角脈沖代碼如下: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)');圖形繪制如下: