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School of Electrical, Computer and Telecommunications Engineering, University of Wollongong
Review Tutorial Questions
:
Sampling & Aliasing  Part 1

41 The term “sequence” may be used to refer to a discretetime signal. What is the
reason(s)? Also, terms such as wave, waveform, signal, and function are used for
referring to CT and DT entities. Make a table listing terms, including sequence, are
used in this context and give very brief explanations for each.
42 Briefly discuss the difference between an ideal continuous to discrete converter
and a practical analogue to digital converter. Include corresponding block diagram
representations for both systems in your explanations.
43 Discretetime frequency is dimensionless. Provide some explanations through
comparing it with angular frequency (circular or radian frequency) and show how an
identical discretetime frequency could be resulted from an infinite number of
continuoustime sinusoid waves.
44 Aliasing is solely due to the fact that trigonometric functions are periodic with
period 2π. Using a numerical example (mathematical formula) show aliases in
discretetime sinusoids are generated because of the simple and well known
trigonometric identity of
cos(
θ
+
2
π
)
=
cos(
θ
)
4 5 Suppose that a discretetime signal x[n] is given by the formula shown
here;
x
[
n
]
=
2.2 cos(0.3
π
.
n
−
π
/ 3)
and that was obtained by sampling a continuoustime
signal of
x
(
t
)
=
A
cos(2
π
.
f
0
t
+
φ
)
at a sampling rate of 6000 samples per second.
Determine three continuoustime signals that could produced x[n]. All these
continuoustime signals should have a frequency less than 8kHz. Write the
mathematical formula for all three.
46 (a) From engineering point of view, an ideal Continuous to Discrete converter is
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