quiz3solns09 - EE 230B Quiz 3 Solution Spring 2009 UCLA...

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EE 230B Quiz 3 Solution Spring 2009 UCLA Electrical Engineering Department Prof. G. Pottie Consider the following channel: z -1 2 -1/2 X X 2 -1/2 Σ To this is added AWGN with variance N 0 = 0.01. a) Determine and sketch the folded spectrum. Why would linear equalization be a poor choice for this channel? Form the autocorrelation function X(z): X ( z ) = 1 2 z 1 + 1 + 1 2 z 1 Then substitute for z: Xe j ω T () = 1 + 1 2 e j T + e j T = 1 + cos( T ) The cosine goes to -1 at half the period, that is, at an angular frequency of π. Thus, there is a null at the edge of the Nyquist interval, with the shape looking like a raised cosine filter. Linear equalization works poorly with in-band nulls in the folded spectrum. b) A DFE with two forward filter coefficients c 0 and c -1 will be used, along with a feedback filter with one coefficient c 1 . That is, K 1 = K 2 =1 Determine the minimum mse solution for the coefficient set. Following the formula, obtain 1/2 + N 0 1 + N 0 c 0 c 1 = 1/ 2
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This note was uploaded on 03/29/2011 for the course EECS 100 taught by Professor Dun during the Spring '11 term at CSU Channel Islands.

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quiz3solns09 - EE 230B Quiz 3 Solution Spring 2009 UCLA...

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