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

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?

Answer 1

[David Goodmanson]

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.

[Poorva Limaye]

@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]

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.