WorksheetsExperiment No.1: Generation of Discrete Time Signals
Total questions: 20
Worksheet time: 10mins
Which statement best describes a discrete-time signal?
It is defined at every instant of time without gaps.
It is defined only at specific, separate time points like every minute or hour.
It is a picture that never changes over time.
It is a sound that is always continuous.
In the unit step sequence u(n−n0), what value does the signal take when n ≥ n0?
0
−1
1
n0
A MATLAB script creates an exponential sequence using n=0:1:20; y=exp(-.3*n); What trend will y show as n increases?
It stays constant at 1.
It increases without limit.
It decreases as n gets larger.
It switches between 1 and −1.
Which MATLAB function is suggested to draw continuous-time signals according to the instructions?
stem
plot
hold
title
In discrete-time practice, a delayed unit sample sequence with a delay of 15 samples means the impulse occurs at which index relative to n=0?
At n = 0
At n = 15
At n = -15
At n = 1
A unit step sequence advanced by 8 samples will shift the step so it starts at which index?
n = 0
n = -8
n = 8
n = 1
The instruction lists an exponential sequence with a = 1.2. For discrete-time, which statement best describes what happens to the sequence values as n increases?
They stay constant.
They decrease toward zero.
They grow larger (increase).
They alternate between 1 and -1.
A sinusoidal sequence is to be generated with frequencies 0.8, 1.5, and 4. Which choice shows these as increasing from lowest to highest frequency?
4, 1.5, 0.8
0.8, 4, 1.5
1.5, 0.8, 4
0.8, 1.5, 4
The discrete-time sequence x[n] = 2δ[n] + 3δ[n−1] − 5δ[n−3] contains impulses. Which index has the largest positive weight?
n = −3
n = 0
n = 1
n = 3
For the exponential sequence x[n] = (0.8)n u[n], what happens to x[n] as n becomes larger?
It grows without bound.
It stays at 0.8.
It decreases toward zero.
It flips sign every step.
Which statement best describes a continuous-time signal?
A signal that changes only at separate steps in time
A signal x(t) defined for every moment of time as a continuous variable
A list of numbers stored in a computer
A picture drawn on graph paper
A continuous-time signal x(t) is periodic if there is a positive nonzero value T such that:
x(t + T) = 0 for all t
x(t + T) = x(t) for all t
x(t) = T for all t
x(T) = t for all T
In the MATLAB examples, which command is used to generate a sine wave y from time t?
y = cos(2*pi*t)
y = square(t)
y = sinc(t)
y = sin(2*pi*t)
Which choice best describes a delayed sine wave with a delay of 5 seconds?
The sine wave starts 5 seconds later along the time axis.
The sine wave gets taller by 5 units.
The sine wave becomes a straight line after 5 seconds.
The sine wave speeds up and completes more cycles in 5 seconds.
When the time duration shown for a waveform is increased, what is the most likely effect on what you see in the plot?
You can see more cycles of the wave across the screen.
The frequency of the wave must always increase.
The amplitude of the wave doubles automatically.
The wave disappears after a short time.
Which operation combines two signals by adding their values at each time n?
Signal multiplication
Signal addition
Signal shifting
Signal folding
In signal processing, what does shifting by k do to a signal x(n)?
Flips the signal around n = 0
Multiplies each sample by k
Moves each sample to become x(n − k)
Adds k to each sample value
Which sequence represents a single spike only at n = 0?
Unit step sequence u(n)
Unit impulse sequence δ(n)
Gaussian random sequence w(n)
Cosine sequence cos(0.04πn)
Which statement correctly describes an even signal xe(n)?
xe(−n) = −xe(n)
xe(−n) = xe(n)
xe(n) = 0 for all n
xe(n) + xo(n) = 0
A real sequence x(n) can be split into two parts. Which option shows the correct formulas for these parts?
xe(n) = 1/2[x(n) − x(−n)] and xo(n) = 1/2[x(n) + x(−n)]
xe(n) = x(n) and xo(n) = −x(n)
xe(n) = 1/2[x(n) + x(−n)] and xo(n) = 1/2[x(n) − x(−n)]
xe(n) = x(−n) and xo(n) = x(n)
