Wald Decomposition Theorem Any zero mean covariance stationary processxt can be represented in the form of xt = 1X j =0 dj t j + j ; where d0 = 1 ; 1X j =0 d 2 j < 1 The termt is white noise and represents the prediction error defined to bet = xt P[xt j xt 1;]...
Spectrum Analysis 1 Population Spectrum A random variable Yt, which follows weak stationary process, can be represented as a weighted sum of cos(!t) and sin(!t), letting! be a certain frequency. The form of this represantation is Yt = + Z 0 (!)cos(!t)d! + Z ...