第二章测试1.A discrete-time signal is represented as a sequence of numbers called samples.（ ）
A:对 B:错
答案:A
2.Shift sequence x(n) to the right by m samples, for m>0, resulting in a new sequence （ ）.
A:x(n-m) B:x(-n-m) C:x(-n+m) D:x(n+m) 3.Real-Valued Exponential Sequence anu(n) must decay exponentially as n increases.（ ）
A:对 B:错 4.A sinusoidal sequence is expressed by
, thus its period is （ ）.A:6 B:11 C:12 D:12/11 5.Frequencies in the neighborhood of
are called low frequencies, whereas, frequencies in the neighborhood of 
are called high frequencies.（ ）A:错 B:对 6.For the following system, which one is linear system? （ ）
A:
B:
C:
D:
7.The impulse response h(n) is the output of a LTI system with zero state when the input is the unit sample sequence δ(n). （ ）A:错 B:对 8.To compute the output of LTI system described by difference equation, the main methods involve in （ ）.
A:computation using MATLAB B:classical solution from time domain C:solution from transform domain D:recursive solution from time domain 9.A discrete time sequence x(n) is developed by periodically sampling an analog signal xa(t) at uniform time intervals, thus the spectrum of discrete time signal x(n) should be periodic extension of the spectrum of the original analog signal.（ ）
A:错 B:对 10.In the process of converting analog signals to digital signals, the higher the sampling frequency is, the better the processing performance of the system will be.（ ）
A:对 B:错 11.To recover the original continuous signal from the sampled signal without distortion, Which conditions should be satisfied?（ ）
Ⅰ. The original continuous signal should be bandlimited；
Ⅱ. The sampling rate of signals should be greater than twice the signal bandwidth；
Ⅲ. The ideal lowpass filter should be used to process the sampled signal.
A:Ⅰ、Ⅱ、Ⅲ B:Ⅱ、Ⅲ C:Ⅰ、Ⅱ D:Ⅰ、Ⅲ
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