Translations:Frequency response of a digital system/51/en

${\begin{aligned}\sum _{k=0}^{\infty }{y_{k}^{2}}={\frac {\Delta t}{2\pi }}\int \limits _{-\pi /\Delta t}^{\pi /\Delta t}{|}P\left(e^{i\omega \Delta t}\right)U\left(e^{i\omega \Delta t}\right){|}^{2}d\omega .\end{aligned}}$

(87)