Spectrum graph from sinusoidal signal in wavelength

조회 수: 1 (최근 30일)
Joel Ruiz
Joel Ruiz 2020년 9월 23일
답변: Ameer Hamza 2020년 9월 24일
Hello everybody:
I need to plot in Matlab an intensity modulation from and optical source. First, I need to calculate FFT of the sinusoidal signal of the source but instead of using an x-frequency axis I need to use and x-wavelength axis.
How can I do that?
  댓글 수: 2
Ameer Hamza
Ameer Hamza 2020년 9월 24일
But frequency in fft() starts from 0. That will translates to a wavelength of infinity. Which range do you want to use?
Joel Ruiz
Joel Ruiz 2020년 9월 24일
From 700 nm to 1560 nm

댓글을 달려면 로그인하십시오.

채택된 답변

Ameer Hamza
Ameer Hamza 2020년 9월 24일
This is a modified version of the example on MATLAB fft() documentation page. For this example, I assume wavelength = 1/f. And I restrict the wavelength in range 0.003 to 1.
Fs = 1000; % Sampling frequency
T = 1/Fs; % Sampling period
L = 1500; % Length of signal
t = (0:L-1)*T; % Time vector
S = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t);
X = S + 2*randn(size(t));
Y = fft(X);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
lambda = 1./f;
idx = (lambda > 0.003) & (lambda < 0.1);
lambda = lambda(idx);
P1 = P1(idx);
plot(lambda, P1);
xlabel('wavelength');
ylabel('amplitude')

추가 답변 (0개)

카테고리

Help CenterFile Exchange에서 Fourier Analysis and Filtering에 대해 자세히 알아보기

Community Treasure Hunt

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

Start Hunting!

Translated by