if LTI → ω=ΩT\omega = \Omega Tω=ΩTtotal LTI DT system is H(jΩ)H(j\Omega)H(jΩ) with samplingcenter discrete system is h[n]h[n]h[n] H(ejω)=Hc(jΩ)H(e^{j\omega}) = H_c(j\Omega)H(ejω)=Hc(jΩ)