- $ y[n] - y[n-1] = x[n]| $
- $ \Rightarrow H(\omega) = \frac {1}{1 - e^{-j \omega}} $
From table in book:
- $ \begin{align} u[n] &\overset {\mathfrak{F}}{\longleftrightarrow} \frac {1}{1 - e^{-j \omega}} + \sum_{k=-\infty}^{\infty} \pi \delta (\omega - 2 \pi k) \\ 1 &\overset {\mathfrak{F}}{\longleftrightarrow} 2 \pi \sum_{l=-\infty}^{\infty} \delta (\omega - 2 \pi l) \end{align} $