In[]:=
f={120,50};;fs=300;L=1000;dt=1/(fs);​​fnc=Total[Sin[2Pi#ndt]&/@f]​​dsignal=Table[fnc,{n,L}];​​dft=Fourier[dsignal,FourierParameters{1,-1}];​​d=Table
(t-1)
Ldt
,2.
Abs[dft[[t]]]
L
,t,1,
L
2
;​​ListPlot[d,Filling->Axis]​​
Out[]=
Sin
nπ
3
+Sin
4nπ
5

Out[]=
In[]:=
Clear["Global`*"]
In[]:=
fnc
Out[]=
{0,0}