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Discrete Fourier Transform
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Discrete Fourier Transform Pairs and Properties (info) | |
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Definition CT Fourier Transform and its Inverse | |
Discrete Fourier Transform | $ X [k] = \sum_{n=0}^{N-1} x[n]e^{-j 2\pi \frac{k n}{N}} \, $ |
Inverse Discrete Fourier Transform | $ \,x [n] = (1/N) \sum_{k=0}^{N-1} X[k] e^{j 2\pi\frac{kn}{N}} \, $ |
Discrete Fourier Transform Pairs (info) | |||
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$ x[n] \ $ | $ \longrightarrow $ | $ X[k] \ $ | |
$ \ \delta[n] $ | $ \ 1 $ | ||
$ \ 1 $ | $ \ N\delta[k] $ | ||
$ \ e^{j2\pi k_0 n} $ | $ \ N\delta[((k - k_0))_N] $ | ||
$ \ \cos(\frac{2\pi}{N}k_0n) $ | $ \ \frac{N}{2}(\delta[((k - k_0))_N] + \delta[((k+k_0))_N]) $ |
Discrete Fourier Transform Properties | |||
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$ x[n] \ $ | $ \longrightarrow $ | $ X[k] \ $ | |
Linearity | $ ax[n]+by[n] \ $ | $ aX[k]+bY[k] \ $ | |
Circular Shift | $ x[((n-m))_N] \ $ | $ X[k]e^{(-j\frac{2 \pi}{N}km)} \ $ | |
Duality | $ X[n] \ $ | $ NX[((-k))_N] \ $ | |
Multiplication | $ x[n]y[n] \ $ | $ \frac{1}{N} X[k]\circledast Y[k], \ \circledast \text{ denotes the circular convolution} $ | |
Convolution | $ x(t) \circledast y(t) \ $ | $ X[k]Y[k] \ $ | |
time reversal | $ \ x(-t) $ | $ \ X(-f) $ |
Other Discrete Fourier Transform Properties | |
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Parseval's Theorem | $ \sum_{n=0}^{N-1}|x[n]|^2 = \frac{1}{N} \sum_{k=0}^{N-1}|X[k]|^2 $ |