Fourier Transform

Creator
Creator
Seonglae Cho
Created
Created
2020 Aug 23 10:56
Editor
Edited
Edited
2024 Dec 21 12:53

Linear transformation between time signal vector & frequency vector

The
Wavelet Transform
is a means of moving between
Locality
and
Universality
preserving properties, while
Fourier Transform
’s frequency-based representation is merely one efficient choice.
Unlike
Fourier Series
we do not use
Periodic signal
Tilda function
. By Fourier Transform out purpose is transforming aperiodic signal to periodic signal. We let the infinite long period for representing Fourier transform. and then ω0\omega_0 goes to 0, then w0kww_0k \rightarrow w become a variable.
In the non-periodic case, the set of frequencies becomes continuous, meaning that there are an infinite number of frequencies present. This is because non-periodic signals cannot be represented as a sum of harmonically related sinusoids, which is the case for periodic signals. Instead, non-periodic signals can be represented as a sum of sinusoids with continuously varying frequencies.
Fourier transform
X(jt)=x(t)ejwtdtX(jt) = \int_{-\infty}^\infty x(t)e^{-jwt}dt
Inverse Fourier transform
x(t)=12πX(jω)ejωtdωx(t) = \frac{1}{2\pi}\int_{-\infty}^\infty X(j\omega)e^{j\omega t}d\omega
X(jtω0)=TakX(jt\omega_0) = Ta_k with duration T for any limited signal x(t)x(t) (relation between
Fourier coefficient
)
F{gh}=F{g}F{h}F1{gh}=F1{g}F1{h}F\{g\ast h \} = F\{g\}F\{h\} \rightarrow F^{-1}\{gh\} = F^{-1}\{g\} \ast F^{-1}\{h\}
Fourier Transform Notion
 
 
Fourier Transform Usages
 
 
 
https://www.youtube.com/watch?v=Nupda1rm01Y
 
 

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