Chapter+2+Review_Answer有详细的答案.pdfVIP

Chapter 2 1. Determine which one of the following four discrete-time systems is linear and shifting-invariant. (C) (A) y (n ) x (n =−2) (B) y (n ) nx (n −3) (C) y (n) x(n =−1)cos w0 (D) y (n) ex (n ) 2. Determine which one of the following four discrete-time systems is linear and stable. (C) (A) y (n ) ln[x (n =−2)] (B) y (n ) nx (n −3) (C) y (n) x(n =−1)cos w0 (D) y (n) 3ex (n ) 3. Determine which one of the following four discrete-time systems is shift-invariant and casual. (C) (A) y (n ) x (n =+1) ⋅x (n ) (B) y (n ) x (n ) / n π (C) y (n ) tan( )x (n −1) (D) y (n ) x (2n ) −x (n −1) 4 4. Determine which one of the following sequences is not a periodic sequence. ：( D) π (A) x (n) cos(50πn) (B) x (n ) cos(1.3πn + ) +4 4 5 (C) x n 2 πn (D) x (n) ejn /5 ( ) sin ( ) 3 3π π 5. A digital signal x (n ) cos( n − ) , then its period is： C 7 8 (A) 7 (B) 14/3 (C) 14 (D) ∞ 11 π 6. The period of digital signal x (n ) sin( n =− ) is: D 3 4 (A) 3 (B) 6 (C) 11 (D) ∞ 7. There is a LTI system, when the input signal is x (n) δ(n) , the output is y (n ) R (n ) , then when the input is U ( n) −U ( n −2) , the output will be： C (A) R (n) (B) R (n −1)