17.5 Power Densitv SDectrii 425 (17.62) er Describing ramloni sigrials with exptctcd vdiscs aiid in particular wit IT correlation firrtc'2 i o r tdirwed ~ that the properties of' rwritloin sigsials can ktc cxpressed by deterrrrinistic ~ ~ i a ~Iristead t ~ ~of ~ a raritiorn ~ s t iinc signal there would f w ~for cximiple thci [ l ( ~ t ~ r ~ i ~attto-rorrclatioi istic function which is tiktwiw r2 tletermiuistic qiinntity In the past chap we saw that describing signals in the freyuertc)r-cloinain is