生成一段Chirp信号进行分数阶傅里叶变换并画出三维图的MATLAB代码
时间: 2023-12-02 07:02:06 浏览: 50
以下是生成Chirp信号并进行分数阶傅里叶变换的MATLAB代码:
```matlab
% Generate Chirp signal
t = 0:0.001:1;
f0 = 50;
f1 = 100;
T = 1;
K = (f1-f0)/T;
phi = 2*pi*f0*t + pi*K*t.^2;
x = cos(phi);
% Fractional Fourier transform parameters
alpha = 0.5;
beta = 1 - alpha;
% Fractional Fourier transform
y = fracft(x,alpha);
% Fractional Fourier spectrum
w = -pi:0.01:pi;
a = exp(-1i*alpha*pi/2);
b = exp(-1i*beta*pi/2);
s = zeros(length(w),length(w));
for k = 1:length(w)
for l = 1:length(w)
s(k,l) = a*b^(k-1)*(cos(w(l))^alpha*1i*sin(w(l))^beta)*fracft(a*b^(k-1)*x,beta)';
end
end
% Plot results
figure;
subplot(2,2,1);
plot(t,x);
title('Chirp signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(2,2,2);
plot(t,y);
title(['Fractional Fourier transform (\alpha=',num2str(alpha),')']);
xlabel('Time (s)');
ylabel('Amplitude');
subplot(2,2,[3,4]);
surf(w,w,abs(s));
title(['Fractional Fourier spectrum (\alpha=',num2str(alpha),')']);
xlabel('\omega_1');
ylabel('\omega_2');
zlabel('Magnitude');
```
执行代码后,将会生成一个包含Chirp信号、分数阶傅里叶变换结果和分数阶傅里叶谱的图形窗口。其中,分数阶傅里叶谱是一个三维图,横轴和纵轴分别表示两个频域变量 $\omega_1$ 和 $\omega_2$,纵轴表示幅值。
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