Interpolation via Zero Padding

Question

Zaref Li 2024-1-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2066091-interpolation-via-zero-padding

评论： Sulaymon Eshkabilov 2024-1-5

Hello everyone,

Below is the interpolation code with zero padding. But I want to make some changes to this code. I want to interpolate by a factor of 5 in the time domain using the following. Which factor component should I change here? Can you help me?

N = 30;   
x = (0:N-1)/N;
Ni = 300; 
xi = (0:Ni-1)/Ni;
f = exp.(sin.(2*pi*x));
ft = fftshift(fft(f))
Npad = floor(Int64, Ni/2 - N/2)
ft_pad = [zeros(Npad); ft; zeros(Npad)];
f_interp = real(ifft( fftshift(ft_pad) )) *Ni/N ;
plot(x,f, label="Original samples",markershape=:circle)
plot!(xi,f_interp,label="Interpolated values")

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Sulaymon Eshkabilov 2024-1-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2066091-interpolation-via-zero-padding#answer_1382691

在 MATLAB Online 中打开

Is this what you are trying to get:

N = 30;

x = (0:N-1)/N;

Ni = 5 * N; % By a factor "5"

xi = (0:Ni-1)/Ni;

f = exp(sin(2*pi*x));

ft = fftshift(fft(f));

Npad = floor((Ni/2 - N/2));

ft_pad = [zeros(1, Npad), ft, zeros(1, Npad)];

f_interp = real(ifft(fftshift(ft_pad))) * Ni / N;

plot(x, f, 'ro', 'MarkerFaceColor', 'y', 'DisplayName',"Original samples"), hold on

plot(xi, f_interp, 'b-', 'LineWidth',2, 'DisplayName',"Interpolated values")

legend('show')

xlabel('x')

ylabel('f(x)')

grid on

2 个评论
显示无隐藏无

Zaref Li 2024-1-5

Thank you for your help. Can I ask a question? If we want to change the signal with cos(2*pi*0.2*n) n:0:1:15. Where do I need to make a change?

Sulaymon Eshkabilov 2024-1-5

在 MATLAB Online 中打开

It would be something like this one:

N = 16;

x = (0:N-1)/N;

Ni = 5*N; % By a factor "5"

xi = (0:Ni-1)/Ni;

f = exp(cos(2*pi*0.2*x));

ft = fftshift(fft(f));

Npad = floor((Ni/2 - N/2));

ft_pad = [zeros(1, Npad), ft, zeros(1, Npad)];

f_interp = real(ifft(fftshift(ft_pad))) * Ni / N;

plot(x, f, 'ro', 'MarkerFaceColor', 'y', 'DisplayName',"Original samples"), hold on

plot(xi, f_interp, 'b-', 'LineWidth',2, 'DisplayName',"Interpolated values")

legend('show', 'Location', 'Best')

xlabel('x')

ylabel('f(x)')

grid on

请先登录，再进行评论。

Answer 2

Balaji 2024-1-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2066091-interpolation-via-zero-padding#answer_1382706

在 MATLAB Online 中打开

Hi Zaref

To interpolate by 'interpolate_size=5' you can assign

Ni = N*interpolate_size

You can modify your code as below:

N = 30;   
x = (0:N-1)/N;
interpolate_size = 5;
Ni = N*interpolate_size; 
xi = (0:Ni-1)/Ni;
f = exp(sin(2*pi*x));
ft = fftshift(fft(f));
Npad = floor(Ni/2 - N/2);
ft_pad = [zeros(1, Npad) ft zeros(1, Npad)];
f_interp = real(ifft( fftshift(ft_pad) ))*Ni/N ;
figure(1)
stem(x,f)
figure(2)
stem(xi,f_interp)