17 11)escribiiig Rimdoin Signals 432 Figure 17.12: Power density spectrum of t h r cliscrctc random proce8s q L s the mto-correlation srquences ( p i p ( t ) ,the power density spectrum of the discrete random process @zz (eJQ) is sirnply the periodic continuation of the power driisity spectrum a,, (p), in accordance with (11.33) Exercises xereise 17.1 For which of the following ensembles might hold: