On Feb 8, 5:18=A0am, "nasim ." <nasim...@yahoo.com> wrote:
> yuva...@gmail.com wrote in message <aacacfe681244e499700
>
> 02dbbbcea...@l32g2000hse.googlegroups.com>...
>
> > On Feb 8, 11:09 am, "nasim ." <nasim...@yahoo.com> wrote:
> > > I have a signal
> > > d(2*pi*t)=3Dactran(2*cost(2*pi*t)4)+.89
> > > Can some one advise how/if =A0I can do a numerical
> > > calculation for Fourier Transform of this signal in
> Matlab?
>
> > > Thank you
>
> > in order to do that numerically define a large vector
> of "t" (with
> > your desired resolution), create the vector of "d", and
> perform fft on
> > "d". Note that you should supply the window size
> according to the
> > desired accuracy.
> > But, if you have the d(t) analytically, why use a
> numerical
> > calculation.
>
> actually i know the transform is going to be in the form of
> d(wt+phi)=3Ds*cos(wt+phi)+d2(wt+phi)
NO!
The complex transform X WILL NOT be a function of t.
The complex transform X will be a function of f.
The original signal x(t) can be expressed as a sum
of sinusoids with amplitudes, frequencies and phases determined by the
amplitudes and phases of the vector
X at the discrete frequencies in f.
doc fft
help fft
> I am trying to find a numerical value for the fourier
> series coefficient s.
Look at plot(f,abs(X)). The peaks will indicate the
dominant frequencies. However is not obvious to me
that one frequency will be so dominant that the others
can be neglected.
What dominant frequencies and peaks are you getting
when N =3D 128 and T =3D 2*pi?
Hope this helps.
Greg
