1. A signal that is a function of time has the following properties (or the following applies to it).
It may originate from an electrical or a nonelectrical system (e.g., mechanical).
It cannot be periodic.
It must always be periodic.
It must always be discrete and never analog or continuous.
2. A sinusoidal signal, 20 sin(ωt + π/2 ), passing through an LTI system, undergoes a gain of 2 and a 90-degree phase lag. The resulting output signal will be mathematically described as
22 sin(ωt + π/2).
40 sin(ωt ).
10 sin(ωt + π/2).
40 sin(ωt - π/2).
3. Determine which of the following is a linear system by applying the principle of superposition.
y = 0.5 x +0.5
y = 0.5 x -0.5
y = .5 x
y = 0.5 x2
4. A continuous time system has an output, y, which is a function of time and is given by . It is sampled at a frequency of 1 Hz. Determine the expression that correctly represents the discrete signal obtained after sampling and its value for n = 3.
y(n) = 3 n3 , value at n = 3 is 81.
y(n) = 5 n3 , value at n = 3 is 135
y(n) = 6 n2 , value at n = 3 is 54
y(n) = n3 , value at n = 3 is 27
5. A signal given by 5 Cos (20*pi*t) + 20 Sin (40*pi*t) is sampled at a rate of 50 Hz. Is the Nyquist theorem violated?
No, it is not violated.
Yes, it is violated.
Insufficient data to answer the question
Question cannot be answered because sampling time is unknown
6. A sawtooth wave repeats itself every 0.05 seconds. The first three harmonics in this sawtooth wave have a frequency of
0.05, 0.1, 0.15 Hz.
40, 80, 120 Hz.
20, 40, 60 Hz.
50, 100, 150 Hz.
7. A discrete time sequence is shown below in a figure. All values not shown can be assumed to be zero. Describe the sequence as a sum of undelayed (if any) and delayed step functions.
- 2δ(n-1) - 2 δ(n-2) + δ (n-3) +δ (n-4)
δ(n-1) - 2 δ(n-2) - 2 δ (n-3) - δ (n-4)
-2δ(n) - δ(n-1) - δ (n-2) + + δ(n-3)
δ(n-1) + 2 δ(n-2) + δ(n-3) +2 δ (n-4)
8. A discrete time sequence is shown below in a figure. All values not shown can be assumed to be zero. Describe the sequence as a sum of undelayed (if any) and delayed step functions.
2U(n) -3 U(n-1)
2U(n-1) - 3U(n-2)
2U(n-1) -3 U(n-2) + U(n-3)
2U(n) +3 U(n-1) - U(n-3)