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| Time Shifting & Frequency Shifting || 1) <math>x[n - n_{o}] \rightarrow e^{-j\omega n_{o}}\chi(\omega)</math><br /> | | Time Shifting & Frequency Shifting || 1) <math>x[n - n_{o}] \rightarrow e^{-j\omega n_{o}}\chi(\omega)</math><br /> | ||
2) <math>e^{-j{\omega}_{o}n}x[n] \rightarrow \chi[\omega - \omega_{o}]</math><br /> | 2) <math>e^{-j{\omega}_{o}n}x[n] \rightarrow \chi[\omega - \omega_{o}]</math><br /> | ||
| − | || | + | || <math>\mathfrak{F}(x[n - n_{o}]) = \sum_{n=-\infty}^{\infty}x[n - n_{o}]e^{-j\omega n}</math><br /> |
| + | let <math> m = n - n_{o} </math><br /> | ||
| + | <math>\sum_{m=-\infty}^{\infty}x[m]e^{-j\omega m + n_{o}} </math><br /> | ||
| + | <math>= e^{-j\omega n_{o}}\sum_{m=-\infty}^{\infty}x[m]</math> | ||
| + | <math>= e^{-j\omega n_{o}}\chi(\omega)</math> <br /> | ||
| + | ________________________________<br /> | ||
|- | |- | ||
| Conjugate & Conjugate Symmetry || <math>x[n] \rightarrow \chi^{*}(-\omega)</math> || <math></math>________________________________<br /> | | Conjugate & Conjugate Symmetry || <math>x[n] \rightarrow \chi^{*}(-\omega)</math> || <math></math>________________________________<br /> | ||
Revision as of 23:07, 18 March 2018
Discrete-Time Fourier Transform Properties with Proofs
| Property Name | Property | Proof |
|---|---|---|
| Periodicity | $ \chi(\omega + 2\pi) = \chi(\omega) $ | $ \chi(\omega+2\pi) = \sum_{n=-\infty}^{\infty}x[n]e^{-j(\omega +2\pi)n} $ $ = \sum_{n=-\infty}^{\infty}x[n]e^{-j\omega n} e^{-j\omega 2\pi} $
|
| Linearity | $ ax_{1}[n] + bx_{2}[n] \rightarrow a\chi_{1}(\omega) + b\chi_{2}(\omega) $ | $ \mathfrak{F}(ax_{1}[n] + bx_{2}[n]) = \sum_{n=-\infty}^{\infty}[ax_{1}[n] + bx_{2}[n]]e^{-j\omega n} $ $ \sum_{n=-\infty}^{\infty}ax_{1}[n]e^{-j\omega n} + \sum_{n=-\infty}^{\infty}bx_{2}[n]e^{-j\omega n} $ |
| Time Shifting & Frequency Shifting | 1) $ x[n - n_{o}] \rightarrow e^{-j\omega n_{o}}\chi(\omega) $ 2) $ e^{-j{\omega}_{o}n}x[n] \rightarrow \chi[\omega - \omega_{o}] $ |
$ \mathfrak{F}(x[n - n_{o}]) = \sum_{n=-\infty}^{\infty}x[n - n_{o}]e^{-j\omega n} $ let $ m = n - n_{o} $ |
| Conjugate & Conjugate Symmetry | $ x[n] \rightarrow \chi^{*}(-\omega) $ | ________________________________ |
| Parversal Relation | $ \sum_{n=-\infty}^{\infty }\left | x[n] \right |^{2} = \frac{1}{2\pi }\int_{0}^{2\pi}\left | \chi (\omega) \right |^{2}d\omega $ | ________________________________ |
| Convolution | $ x[n]*y[n] \rightarrow \chi(\omega)\gamma (\omega) $ | ________________________________ |
| Multiplication | $ x[n]y[n] \rightarrow \frac{1}{2\pi}\chi(\omega)*\gamma (\omega)^{}_{} $ | ________________________________ |
| Duality | NO DUALITY IN DT | NO DUALITY IN DT________________________________ |
| Differentiation in Frequency | $ nx[n] \rightarrow j\frac{\mathrm{d} }{\mathrm{d} \omega}\chi(\omega) $ | ________________________________ |
