# How to Calculate the Period of the Discrete Time Sequence from Taking Its DFT

This is my discrete time periodic signal, the time resolution of the samples is 0.2ms.

And it's periodic after each 11 samples. So the fundamental period of the signal is 2ms or the fundamental frequency of this sequence is 500Hz. The amplitude of each pulse increases from -5V with unit step to +5V.

But I want to find its frequency (which is 500 Hz) by calculating its FFT and plot of FFT spectrum. Please help me. Thank you.

Sample the signal into MATLAB.
Apply the fft function on it.

Plot the absolute value of the DFT signal (Its first half of samples).
Look for its peak, the index number of the peak multiplied by the sampling frequency divided by the number of samples will give the frequency.