A stable causal LTI system has the frequency response H$().$ Let C$()=|$H$()|2$ and let

C$($z$)=(1+$ z $2$z$2)(1+$ z$12$z$2)$

$(10\mathrm{.}82$z$1+0\mathrm{.}64$z$2)(10\mathrm{.}82$z $+0\mathrm{.}64$z$2)$