MATLAB: Zero padding or not

Question

Hello all,

I want to estimate the spectrum of a part of a signal by using an 1024 point FFT. The length of the excerpt is 640 samples. Should I zero pad the signal to make its length equal to 1024? Or is it automatically done by Matlab?

Answer 1

   fft(x,1024)

Will automatically zero pad your signal to 1024 points and perform FFT