The stationary random process X(t) has a power spectral density denoted by Sx(f).
1. What is the power spectral density of Y(t) = X(t) - X(t-T)?
2. What is the power spectral density of Z(t) = X'(t) - X(t)?
2. What is the power spectral density of W(t) = Y(t) - Z(t)?