How can I transform between Time-Domain and Frequency-Domain?

7 次查看（过去 30 天）
mohammad heydari
mohammad heydari 2021-8-24
回答： TED MOSBY 2024-10-19
Hi,
I encounter the problem of transforming a shape from the time domain to the frequency domain.
I used the following commands to convert Fourier.
n1=8;
n2=72;
nt=25501;
dt=1.176470588235294e-13;
F=zeros(n1+n2+2,nt);
F1=F(n1+n2,:);
F2 = fftshift(fft(F1));
f=linspace(-10,10,length(F2));
figure(1);
plot(f, 10*log10(abs(F2)))
Please do not doubt the values entered such as 'nt' and 'dt' because all the shapes obtained in the time domain are correct and the only problem is in converting the frequency.
Let me know please.
Thank you.

请先登录，再回答此问题。

回答（1 个）

TED MOSBY
TED MOSBY 2024-10-19
Hi Mohammad,
To transform a shape from the time domain to the frequency domain using the Fourier Transform in MATLAB, it seems like you're already on the right track.
Signal Initialization: Instead of initializing F to zeros, I replaced it with a random signal for demonstration. Make sure F1 contains the actual shape data you want to analyze.
Frequency Vector Calculation: The frequency vector f is derived from the sampling frequency, which is computed as Fs = 1 / dt. This provides the correct scaling for the frequency axis.
FFT Handling: The fft function is still used as you had it, but with the proper initialization for F1.
I adjusted your code with the above modifications:
% Parameters
n1 = 8;
n2 = 72;
nt = 25501;
dt = 1.176470588235294e-13;
% Initialize the time-domain signal (example: a random signal)
F = rand(n1 + n2 + 2, nt);
F1 = F(n1 + n2, :);
% Compute the Fourier Transform
F2 = fftshift(fft(F1));
% Frequency vector calculation
Fs = 1 / dt; % Sampling frequency
f = linspace(-Fs/2, Fs/2, length(F2)); % Frequency vector
% Plotting the result
figure(1);
plot(f, 10 * log10(abs(F2))); % Plot in dB scale
xlabel('Frequency (Hz)');
ylabel('Magnitude (dB)');
title('Frequency Domain Representation');
grid on;
The output should look like this:
Hope this helps!

类别

在 Help Center 和 File Exchange 中查找有关 Discrete Fourier and Cosine Transforms 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by