# Properties of the Power Spectral Density of a Generic Random Process

I have a random process Y[t] and associated autocorrelation function $$R_Y[\tau]$$ which is real and symmetric about $$\tau=0$$. $$R_Y[\tau]$$ contains both negative and positive values.

What can be said about the properties of the power spectral density of this random process? You should assume its not wide sense stationary.