A = 1; mi = 2; [Omega]1 = 10; [Omega]m = 1; [Tau] = 0.5; NL = 99;
R = 1; C1 = 2;
Plot[{(ASin[[Omega]1t + miCos[[Omega]mt]] -
ASin[[Omega]1(t - [Tau]) +
miCos[[Omega]m(t - [Tau])]])^2}, {t, 0, NL},
PlotRange → {{0, 30}, {0, 4}}, AxesLabel → {“Time”, " Amplitude"},
GridLines → Automatic, AxesStyle → Directive[Black, 13],
PlotStyle → Directive[Black, 13]]
data = Table[(ASin[[Omega]1t + miCos[[Omega]mt]] -
ASin[[Omega]1(t - [Tau]) +
miCos[[Omega]m(t - [Tau])]])^2, {t, 0, NL, 0.01}];
ListLinePlot[Abs[Fourier[data]], PlotRange → {{0, 500}, {0, 50}},
GridLines → Automatic, AxesLabel → {“Frequency”, “Amplitude”},
PlotStyle → Directive[Blue, 13], AxesStyle → Directive[Black, 13]]
The problem that I am facing while I run this code is: the frequencies that are calculated using Fourier command shows peak of the spectrum near 17 Hz and some other redundant peaks. Now if I filter this signal using a low pass filter, it is expected that the result will be [Omega]m , i.e., N[1/(2*[Pi])]=0.159155 Hz. So, the spectrum that I obtained is not correct. I am using Mathematica 10.0. Please help me. Thanks.
The code for filtering the signal :
ListLinePlot[Abs[Fourier[LowpassFilter[data, 0.01]]], PlotRange -> {{0, 200}, {0, 20}}, GridLines -> Automatic, AxesLabel -> {"Frequency", "Amplitude"}, PlotStyle -> Directive[Blue, 13], AxesStyle -> Directive[Black, 13]]