通信系统综合设计实训1..docx

通信系统综合设计实训1--连续信号的频谱分析班级：0141202姓名：李得钊学号：2012210204一、实验目的1、掌握连续周期信号的各次谐波的分解，周期 T 趋于无穷大时频谱的变化；2、掌握连续非周期信号频谱的 MATLAB 实现；3、对连续信号的频谱有一定感性认识。二、实验内容及步骤1、连续周期信号的傅里叶级数、各次谐波及叠加用 MATLAB 绘制周期方波信号，并绘制其傅里叶级数展开式中基波及 3 次谐波、5 次谐波并进行叠加，与原方波进行对比。实现方波程序：f=sym((Heaviside)(t)-Heaviside(t-0.5)+Heaviside(t-1.5)-Heaviside(t-2.5))),ezplot(f,[0,3]),title(f(t)),xlabel(‘t’),axis([0,3,-0.5,1.5]);grid运行如下绘制基波f=sym(‘(Heaviside)(t)-Heaviside(t-0.5)+Heaviside(t-1.5)-Heaviside(t-2.5))’),ezplot(f,[0,3]),title(‘f(t)’),xlabel(‘t’),axis([0,3,-0.5,1.5]);grid;hold on;t=0:0.001:3;x0=0.5+2/pi*cos(pi*t);plot(t,x0);结果如下加入三次谐波f=sym(‘(Heaviside)(t)-Heaviside(t-0.5)+Heaviside(t-1.5)-Heaviside(t-2.5))’),ezplot(f,[0,3]),title(‘f(t)’),xlabel(‘t’),axis([0,3,-0.5,1.5]);grid;hold on;t=0:0.001:3;x0=0.5+2/pi*cos(pi*t);plot(t,x0);x3=0.5+2/pi*cos(3*pi*t);plot(t,x3);subplot(2,1,2);f=sym(‘(Heaviside(t)-Heaviside(t-0.5)+Heaviside(t-1.5))-Heaviside(t-2.5))’);ezplot(f,[0,3],title(‘合成波形’)，xlabel(‘t’),axis([0,3,-0.5,1.5]));grid;hold on;x03=0.5+2/pi*cos(pi*t)-2/(3*pi)*cos(3*pi*t);polt(t,x03);2、连续周期信号的周期 T 的变化对频谱的影响n=-40:40; A=1; tao=1;T=2; w1=2*pi/T;x=n*tao/T;Fn=A*tao/T*sinc(x);subplot(3,1,1),stem(n,Fn,’.’),title(’tao=1,T-2’),axis([-40,40,-0,11,0.51]),grid;结果如下3、连续非周期信号的频谱用 MATLAB 实现矩形脉冲 f(t)=g1(t)的傅里叶变换。f=sym(Heaviside(t+1)-Heaviside(t-1));F=fourier(f),subplot(2,2,1);ezplot(f,[-2,2]),title(f(t)),xlabel(t),grid;subplot(2.2,2);ezplot(abs(F),[-10,10]),title(|F(w)|),xlabel(w),axis([-9.43,9.43,-0.1,2.2]),grid;subplot(2,2,3);ezplot(F,[-10,10]),title(F(w)),xlabel(w),axis([-9.43,9.43,-0.5,2.2]),grid;w=-10:0.01:10;phase=3.142*rectpuls(w-4.713,3.142)-3.142*rectpuls(w+4.713,3.142);subplot(2,2,4);plot(w,phase),axis([-9,43,9.43,-4,4]),title(φ(w)),xlabel(w),grid;运行结果如下