电子科技大学 学年第 学期信号与系统期 末 考试 A 卷.doc

电子科技大学2014-2015 学年第 1 学期期 末 考试 A 卷 课程名称： 信号与系统 考试形式： 一页纸开卷 考试日期： 20 15 年 1 月 15 日 考试时长： 120 分钟 课程成绩构成：平时 10 %， 半期考试 20 %， 实验 10 %， 期末 60 % 本试卷试题由 二 部分构成，共 5 页。 题号 一 二 合计 得分 1 2 3 4 一、选择填空题（共30分，共 6问，每问5分） 1. Consider two signals and , as shown in Figure 1. The Fourier transform of is . Then the Fourier transform ofshould be（ ）(a) (b) (c) (d) Figure 1 The waveforms of and 2. The convolution sum ( ). (a) (b) (c) (d) not existed 3. Consider a stable discrete-time system, whose system function is a rational function and has only two poles：. The positions of zeros are unknown. The of the system must be ( ). (a) finite duration (b) right-sided (c) left-sided (d) two sided 4.The relation between the input and the output of a causal continuous-time LTI system is described by the differential equation . The system is （ ）(a) Low-pass filter (b) Band-pass filter (c) High-pass filter (d) Band-stop filter 5.The Fourier transform of the signal is shown in Figure 2.The signal may be (a) real and even (b) real and odd (c) pure imaginary and odd (d) pure imaginary and even 6. The Laplace Transform of is （ ）.(a) ， (b) ， (c) ， (d) ， 二、计算题（ 共70分） 1.（1 points）Suppose and are both band-limited signal, where , .Impulse-train sampling is performed on to obtain , as shown in Figure 3 where .Deduce the value of so that for .Specify the range of values for the sampling period T which ensures that =. Figure 3  2.( 18 points ) Consider an LTI system with unit impulse response .The input signal ，where is the unit step function. (a) Sketch. (b) Determine the magnitude and phase response of this system. (c) Determine the output .  3（1分）A causal continuous-time LTI system is given in Figure . (a)Determine the range of the constant K to ensure that the