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Unformatted text preview: Name: ______________________________________ Page 1 of 4 Midterm 1 (Fall 2007) of EE421G: 1. This midterm consists of four singlesided pages. The last page is an extra worksheet. You can tear out any page but make sure all the pages you turn in have your name on them. 2. There are three problems in this exam. You have 50 minutes to finish this exam. 3. You are allowed to use one doublesided page of cheat sheet. Good luck! 1. (Outcome 2, 34 points) Consider the signal + + + = 2 5 sin 2 3 cos ) ( t t t f . a. Is the signal ) ( t f periodic? If yes, what is its period? The period of the cosine function is 2 /3 and that of the sine function is 2 /5. If their sum is periodic with period T, T must be an integral multiples of the period of the constituent components, or T=m2 /3 and T=n2 /5. The smallest integers that satisfy these equations are m=3 and n=5. Since such multipliers exist, f(t) is periodic with period T=2 . b. Write ) ( t f in terms of complex exponentials. f(t) = cos(3t + /2) + sin(5t + /2) = 0.5{exp[j(3t+ /2)]+exp[j(3t+ /2)]}  0.5j{exp[j(5t+ /2)]exp[j(5t+ /2)]} = 0.5[jexp(j3t) jexp(j3t)] 0.5j[jexp(j5t) + jexp(j5t)] = 0.5jexp(j3t) 0.5jexp(j3t) + 0.5exp(j5t) + 0.5exp(j5t) = 0....
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This note was uploaded on 01/12/2010 for the course ENGR 421g taught by Professor Mattrobinson during the Fall '07 term at Kentucky.
 Fall '07
 mattrobinson

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