Hi, use plot(FFTSHIFT(FFT(Y))); You have N samples which corresponds to One Fs(Smapling frequncy) with fftshift you are displaying Spectrum from -Fs/2 to Fs/2 so your x axis would be samples=N/2-1:N/2; X=samples*Fs/N ; plot(x , FFTSHIFT(FFT(Y))); Hope this will work Regards Chalamala Srinivasa Rao Tata Consultancy Services Limited Mailto: chalamala.srao@chal... Website: http://www.tcs.com Jorge Enrique Prada Rojas <pradajorge@prad...> 04/07/2005 09:13 AM To matlab@matl... cc Subject [matlab] Fourier Transform hi everybody I just apply a FFT with 1024 samples (k24), to function (i.e): y=sin(2*pi*2.48e9*x+0.1*rand(1,1025))+1 After calculating those 1024 values, how can I draw its power spectrum? How define frequency axis? Thanks.

hi everybody I just apply a FFT with 1024 samples (k24), to function (i.e): y=sin(2*pi*2.48e9*x+0.1*rand(1,1025))+1 After calculating those 1024 values, how can I draw its power spectrum? How define frequency axis? Thanks.