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沒有 【段考】高二英文 權限，請先開通．

沒有 【段考】高二英文 權限，請先開通．

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1.Given a continuous-time periodic signal Let ak and ω0, be the coefficients and fundamental frequency of the Fourier series of f(t) respectively. Then which of the following statements is correct? (A)(B)(C)(D)a0＜5,ω0＜2,a5＞0. (E) None of the above statements are correct.

2.Consider a discrete signal x(n) = cos(2nr / N), where integer N is the fundamental period. Let a be the coefficients of the discrete-time Fourier series of x(n). Then which of the following statements is correct? (A) a1=-1/2,a2=1/2. (B) a1=a2=j/2 (C) (D) (E) None of the above statements are correct.

3.Consider an LTI system whose impulse response is G(jω)=1/(a+ jω), a ＞ 0. Suppose that there is an input signal X(jω)=1/(a+ jω). Assume that the output signal is y(t)= , where u(t) is a unit-step signal. Then which of the following statements is correct? (A)β+y=-a (B) βy=-a (C) β-y=t+a (D) βy=at (E) None of the above statements are correct.

4.Consider the following three systems, where [n] or x(t) is the system input, y[n] or y(t) denotes the system output, and I.Which of the following statements is correct? (A) I is time-invariant, II is linear, Ill is causal. (B) I is memoryless, II is causal, III is nonlincar. (C) I is stable, II is linear, III is memoryless. (D) I is causal, II is memoryless, III is linear. (E) None of the above statements are correct.