【转载】利用matlab绘制傅里叶分解三维图-装备攻略-剑霸云城武侠游戏活动站

目的：理解傅里叶变换分析及其他方法的分析。理解傅里叶变换频域与时域的关系。利用MATLAB绘制傅里叶变换图形三维图。内容和原理：本次主要使用的函数及其说明如下（此处只取采用用法的意义说明）：1.abs：abs(X) is the absolute value of the elements of X. WhenX is complex, abs(X) is the complex modulus (magnitude) ofthe elements of X.2.figure: figure, by itself, creates a new figure window, and returnsits handle.3.square: square(T) generates a square wave with period 2*Pi for theelements of time vector T. square(T) is like SIN(T), onlyit creates a square wave with peaks of +1 to -1 instead ofa sine wave.4. Fft: fft(X,N) is the N-point fft, padded with zeros if X has lessthan N points and truncated if it has more.5. plot3：plot3(x,y,z), where x, y and z are three vectors of the same length,plots a line in 3-space through the points whose coordinates are theelements of x, y and z.

结果与分析：根据要求需要首先产生具有足够采样频率的方波，我采用了square函数生成方波，频率设置为1Hz，采样频率则为100Hz。接着进行傅里叶变换，利用fft函数，生成N个分解波形，N越大，分解次数越多，频谱越精密，实验中采用N=512进行实验。利用plot3函数进行绘图并投影。产生的方波图如下：

产生频谱图如下：

绘制三维图像如图：

程序代码如下：

N=512;

fs=100;

t=-2:1/fs:2;

m=square(2*pi*t);

plot(t,m);

axis([-1 1 -2 2]);

figure();

title('方波');

b=fft(m,N);

mag=abs(b);

plot(mag);

figure();

x=-5:0.01:5;

for i=1:length(b)

for k=1:length(x)

z(k)=abs(b(i))*sin((i-1)*x(k)+angle(b(i)));

y(k)=i;

end

figure(3);

grid on;

plot3(x,y,z);

hold on;

x_z=zeros(1,length(x))+6;

plot3(x_z,y,abs(z));

hold on;

end