How to convert the x an y axis to frequency in plotting 2D FFT?

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Poorva Limaye 2017-1-4

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编辑： David Goodmanson 2017-1-6

In case of 1D FFT,plot (abs(fft(X)) displays the frequency bin number on x axis and can be converted into frequency by multiplying by (fs/N). How can I convert the x and y axes values to frequency in case of 2D FFT? I have raw data in a matrix form (1024 rows *8 columns).I am plotting 2D FFT using the fft2 function.How can I convert the x and y axes to frequency?

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Answer 1

David Goodmanson 2017-1-5

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编辑：David Goodmanson 2017-1-5

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Hi Poorva, If what you are ffting is truly a 2d time array, then there will be a sampling frequency for each direction. In that case calculation for each independent frequency axis is the same as what you did before:

fy = ny*fsy/Ny fx = nx*fsx/Nx

where ny,nx are bin numbers. If this were not exactly a 2d time-by-time array, there are other possibilities.

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Poorva Limaye 2017-1-5

编辑：Poorva Limaye 2017-1-5

@David : The array represents the values of FMCW wave in radar where each column represents 1 sweep and has 1024 rows that gives the data in each sweep. x axis=number of sweeps=8

David Goodmanson 2017-1-6

编辑：David Goodmanson 2017-1-6

Hi Poorva, I am not sure what doing an fft of the sweeps will achieve, but having no background in any of that there is probably nothing I could say that would be useful. Good luck in your task.

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