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} = e^{-j\omega 2\pi} \sum_{n=-\infty}^{\infty}x[n]e^{-j\omega n} = (1)\chi(\omega) = \chi(\omega) <math>= $ |
| Linearity | $ ax_{1}[n] + bx_{2}[n] \rightarrow a\chi_{1}(\omega) + b\chi_{2}(\omega) $ | Example |
| 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}] $ |
Example |
| 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) $ |
