I have a discrete periodic as in figure http://www​.sp4comm.o​rg/webvers​ion/livre2​8x.png , I want to calculate the period of the sequence from taking its fft(x,N). Can any one help

Hello, http://www.sp4comm.org/webversion/livre28x.png , 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 periodic time of the signal is 2ms or the 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 fequency by calculating its FFT and plot of FFT spectrum. Please help me. Thank you.