practiceexam1

practiceexam1 - (22 pts 1 Let and y(t be the input and the...

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Unformatted text preview: (22 pts) 1. Let and y(t) be the input and the output of a continuous time system, respectively. Answer each of the questions below with either yes or no (no justification needed). Yes No If y(t) : :I:(2t), is the system causal? If y(t) = (if + 2):):(t), is the system causal? If y(t) : 3:(~t2), is the system causal? >5 If y(t) = + t v 1, is the system memoryless? R>< If y(t) : 00(9), is the system memoryless? If y(t) = 113(25/3), is the system stable? l>< If y(t) : 7555(25/3), is the system stable? If y(t) = [:00 513(7‘)d7’, is the system stable? If 3/(25) : sin is the system time invariant? >5 If y(t) 2: u(t) * 513(t), is the system LTI? If y(t) : (tu(t)) * fit), is the system linear? x“? (15 pts) 2. ‘ An LTl system has unit impulse response Mt) : u(t + 2). Compute the system’s response to the input $(t) : e‘tu(t). (Simplify your answer until all 2 signs disappear.) «d , Q ulflu liwde” W0 (15 pts) 3. Compute the energy and the power of the Signal 512(t) : Mm 3*??me Emt 3 MM 3‘: 33%.] gm W «.W «(33% E e w Er-‘M‘V g «L i» Z? :rmim a” " %:eé? :2 A? 22'7"“ e § 3W “T” o W} i" :54??? m g (15 pts) 4. Computethe coefficients ak of the Fourier series of the signal periodic with period T : 4 defined by / _ sinbfl), O§t§2 $(t)_{ 0, 2<t§4' (Simplify your answer as much as possible.) 5. A discrete—time system is such that when the input is one of the signals in the left column, then the output is the corresponding signal in the right column: input output $0 n] = —> yaw] = (5[n m l], :6[n-1] —+ y1[nl:46[n~2], TQM] : 6[n — 2] a yin] : 96in * 3], $3M :6[n~3] —> y3[n] :166[n—4], = (5[n ~ k3] —+ 2 (Is +1)26[n ~ (k: + 1)] for any integer k. - “M (10 PtS) 8) Can this system be time—invariant? Explain. _ V m v.1 E r r ’ lmv. ' i , {2W ' if is xiii} ‘ie 53 i its W 13> it let U i» (10 pts) b) Assuming that this system is linear, What input would yield the output y[n] 2 Mn — 1]? Wei» xiii}: my {33%wa in 2 3 Facts and Formulas CT Signal Energy and Power E00 —/ WNW: T P00 : lim T——>oo 2T VT : Z akejk(27fl)t kzioo 1 T W ak : :I:(t)e’fl”(2T Properties of CT Fourier Series |x(t)[2dt Fourier Series of CT Periodic Signals with period T Let 56(25) be a periodic signal with fundamental period T and fundamental frequency wo. Let y(t) be another periodic signal with the same fundamental period T and fundamental frequency we. Denote by ak and bk the Fourier series coflicients of X(t) and y(t) respectively. Linearity: Time Shifting: Conjugation: Parseval’s Relation Signal 019005) + 6W) :z:(t e to) 93W) real and even ‘ Mt) real and odd FT flak: + 53% (5) e—jkwotoak (6) air (7) ak real and even (8) ak pure imaginary and odd (9) (10) 4: DT Signal Energy and Power E0O : Z (11) P ~ 1' 1 i lrrrlnllg <12) 00 ‘ NEEO2N+1WW 5 Fourier Series of DT Periodic Signals with period N V N~1 ‘ 2 : Z akeJMWfl)” (13) TL _ 2W ak : N a:[n]e’]k(W)n (14) 71:0 6 Properties of DT Fourier Series Let be a periodic signal with fundamental period N and fundamental fre— quency we. Let y[n] be another periodic signal with the same fundamental period N and fundamental frequency we. Denote by ak and bk the Fourier series cofficients of X(t) and y(t) respectively. Signal FT Linearity: arm] + fly 04a;C + fibk (15) Time Shifting: ~ no] e_jk‘“0”0ak (16) Conjugation: 56* afik (17) real and even ak real and even (18) real and odd ak pure imaginary and odd (19) 7 . 1 N—l 2 N—1 2 Parseval 8 Relation. N r; dt — 1;) |akl (20) Properties of LTI systems LTI systems commute. The response of an LTI system with unit impulse response h to a signal 36 is the same as the response of an LT i system with unit impulse response 1: to the signal h. An LTI system consisting of a cascade of k LT I systems with unit impulse responses in, fig, . A . , hk respectively, is the same as an LTI system with unit impulse response hl >k hg * . . . * his. The response of a CT LTI system with unit impulse response h(t) to the signal eSt is H(s)e‘9t where H(s) : ff; h(T)e’STdT. The response of a DT LTI system with unit impulse response h[n] to the signal 2“ is Hm" where He) 2 22:.“ hlklzw ...
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practiceexam1 - (22 pts 1 Let and y(t be the input and the...

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