05上半年《信号》半期试卷 信号与系统本科试卷

共 4 页 第 1 页 学院 任课教师 班次 学号 选课号 姓名 密 封 线 内 答 题 无 效 电电 子子 科科 技技 大大 学学 二二 O O 四四 至至 二二 O O 五五 学年学年 第二学期 阶段测试 第二学期 阶段测试 SIGNALS AND SYSTEMS 课程考试试题 120 分钟 考试日期 2005 年 5 月 15 日 一二三四五六七八九十总分评卷教师 Attention there is only one right answer in the following questions justify your answer and write it in the blank 1 A continuous time signal is illustrated in Figure 1 the closed form expression x t for is dx t dt a 1212u tu tu t b 12122u tu tu tt c 1122u tu tu tt d 12122u tu tu tt 2 2 41 tt dt a 3 b 3 c 5 d 5 3 Consider a discrete time system with input and output related by x n y n this system may be 1y nx n x n a Nonlinear time variant not causal stable b Linear time variant not causal unstable c Nonlinear time invariant not causal stable d Linear time variant causal unstable 1 10 1 2 2 t x t Figure 1 共 4 页 第 2 页 学院 任课教师 班次 学号 选课号 姓名 密 封 线 内 答 题 无 效 4 Consider an LTI system whose response to the signal in Figure 2 is the signal tx1 illustrated in Figure 3 The response of the system to the input depicted in ty1 tx2 Figure 4 is a 21133tu ttu ttu t b 31133tu ttu ttu t c 22233tu ttu ttu t d 21133tu ttu ttu t 5 Consider an LTI system whose input and unit impulse response are given x n h n by 212x nnnn 3122h nnnn The output of this system is nhnxny a 6 1 3 1 1 2 1 0 1 2 3 4y nn b 6 1 5 1 1 2 1 0 1 2 3 4y nn c 6 1 3 1 3 2 1 0 1 2 3 4y nn d 6 1 3 1 1 2 0 1 2 3 4 5y nn 1 tx 012 t 1 Figure 2 10 1 2 t 2 xt 1 1 ty 30 12 1 1 t Figure 3 Figure 4 共 4 页 第 3 页 学院 任课教师 班次 学号 选课号 姓名 密 封 线 内 答 题 无 效 6 The convolution integral may be 1 2 2 1y tu tu tu tu t a 1122233tu ttu ttu ttu t b 2112233tu ttu ttu ttu t c 112233tu ttu ttu ttu t d 112233tu ttu ttu ttu t 7 Let be a periodic signal with fundamental frequency and Fourier series x t 0 coefficients The Fourier series coefficients of is k a 1dx t dt a b c d 0 jk k a e 0 0 jk k jka e 0 0 jk k jka e 0 0 jk k jka e 8 Consider an LTI system with unit impulse response illustrated in Figure 5 if the h t input is the output dt x t dt 3 2t y t a b c d 11 3 2 0 9 The convolution integral may be 2 t y te u t a b c d 2 t e u t 2 t e 1 10 The input signal of an LTI system is if the output 1 n n x ttn the unit impulse response of the system may be cos5cos7y ttt a b 1 sin8s