用Matlab绘制波形

N=1024;

fs=1024;

t=0:1/fs:(N-1)/fs;

x=sin(200*pi*t);

%原始波形

figure

plot(t,x)%%%波形

set(gca,'xlim',[0,0.2],'ylim',[-1.3,1.3])

title('原始波形图')

%频谱分析

a=fft(x);

a=abs(a)*2/N;

f=0:fs/N:(N-1)*fs/N;

figure

plot(f,a)

title('幅频谱图')

%逆变换后时域图

b=ifft(a)*N/2;

figure

plot(t,b)

set(gca,'xlim',[0,0.2],'ylim',[-1.3,1.3])

title('反变换后波形')

%首先可以拟合一个函数：x=(heaviside(n)-heaviside(n-4))+
%(heaviside(n+4)-heaviside(n+1))*(2*n+5);
clear
syms n
x=(heaviside(n)-heaviside(n-4))*6+(heaviside(n+4)-heaviside(n+1))*(2*n+5);
n=-10:0.1:10;
xn=subs(x,n);
plot(n,xn)