test = cell2mat(testS1);
Y = fft(test);
Fs = 3600000;
T = 1/Fs;
L = 141;
t = (0:L-1)*T;
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
plot(f,P1)