I have a spectrum with flux on the Y-axis and wavelength on the X-axis. What I want to do is take the Fourier transform of this spectrum. Then add a random phase between 0 and 2pi to the phase only. Then take the inverse Fourier Transform of this. The piece of code I wrote in IDL for a simple example is below. I was hoping to scramble up the spectrum by doing this. But I am not sure if I have achieved that goal. I have two questions(adsbygoogle = window.adsbygoogle || []).push({});

1. The final spectrum ( for some random phases) are vertically offset from the original spectrum. Why is that so?

2. The amplitude of the final signal varies a lot from the original spectrum for some phases. I wasnt expecting that either. why is that?

3. All I want is that the components of the original spectrum be jumbled up in the X-direction (ie the wavelength direction). How can it be done?

MY CODE :

n = 257

x = FINDGEN(n)

y = COS(x*!PI/6)*EXP(-((x - n/2)/30)^2/2)+x/50.

tek_color

yfft = fft(y)

magnitude = abs(yfft)

angle = ph(yfft)

for count=0, 300 do begin

rand = randomu(seed, 1)*2*!pi

randph = replicate(rand, 256)

fft_signal = magnitude*exp(complex(0,1)*(angle+randph))

ifft_signal = (fft(fft_signal, /inverse))

wait, 0.2

plot, x, y

oplot, x, (ifft_signal), color=2

endfor

end

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# IDL help with FFT.PRO

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

Loading...

Similar Threads - help | Date |
---|---|

Matlab MATLab: Not enough inputs for nlinfit | Nov 16, 2017 |

Matlab Help needed to fix a matlab code | Nov 8, 2017 |

LaTeX Help with page dimensions in latex | Nov 2, 2017 |

Matlab Octave integral computation help | Apr 20, 2017 |

Matlab 2D plotting error help please | Aug 28, 2016 |

**Physics Forums - The Fusion of Science and Community**