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Unformatted text preview: Virginia Tech The Bradley Department of Electrical and Computer Engineering ECE 5605 – Stochastic Signals and Systems – Fall 08 Problem Set 7 Problem 1. Let θ be a random variable uniformly distributed on [0 , 2 π ). Consider the process X ( t ) = cos 2 ( ωt + θ ) . Find the mean value of X ( t ). Problem 2. Let Y ( t ) = X ( t ) aX ( t + d ), where X ( t ) is a Gaussian random process. a. Find the mean and autocovariance of Y ( t ). b. Find the pdf of Y ( t ). c. Find the joint pdf of Y ( t 1 ) and Y ( t 2 ). Problem 3. Let X ( t ) be a zeromean Gaussian random process with autocovariance function given by C X ( t 1 ,t 2 ). If X ( t ) is the input to a “square law detector,” then the output is Y ( t ) = X ( t ) 2 . Find the mean and autocovariance of the output Y ( t ). Hint : If X 1 ,X 2 ,X 3 ,X 4 are zeromean jointly Gaussian random variables, E [ X 1 X 2 X 3 X 4 ] = E [ X 1 X 2 ] E [ X 3 X 4 ] + E [ X 1 X 3 ] E [ X 2 X 4 ] + E [ X 1 X 4 ] E [ X 2 X 3 ] ....
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This note was uploaded on 05/05/2010 for the course ECECS 5605 taught by Professor Dasilver during the Fall '08 term at Virginia Tech.
 Fall '08
 DASILVER

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