how to find out the period of a signal based on its autocorrelation

Question

I'm wondering how the autocorrelation result of a periodic sinal, which period is unkown, reveals information about this perdio, I know how to calcule the autocorrelation, but I just don't understand how can read the period ! from the result! can anyone explain how to do it !

Answer 1

Typically the first peak in the autocorrelation corresponds to the period of the waveform. So for example a 50 Hz sine wave will have a peak in its autocorrelation at t = 1/50 = 0.02s.