Hello Mohammad,
clear all
ts=0.001;
t=0:ts:0.6;
y=5*sin(8*pi*t)+6*sin(16*pi*t);
[p,peaks]=findpeaks(y,'MinPeakProminence',(max(y)-min(y))/4);
Period=mean([diff(peaks(1:2:length(peaks))), diff(peaks(2:2:length(peaks)))])*ts
Or you could work your way arround using autocorrelation
