31
Digital Signals
(cont.)
Example
[
approximation of digital signal’s spectrum using 1
st
harmonic
]
Assume our computer generates 6 bps.
Possibilities (periodic combinations) :
000000, 111111, 110011, 101010 etc.
1.
Best case: min # of changes
min freq. of substitute analog signal
2.
Worst case
–
max # of changes
max freq. of substitute analog signal
bit rate: n = 6 [bps]
frequency:
B = 3 [Hz]
2
n
B

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32
Exercise
1.
Before data can be transmitted, they must be transformed to _______________.
(a)
periodic signals
(b)
electromagnetic signals
(c)
aperiodic signals
(d)
low-frequency sinewaves
2.
In a frequency-domain plot, the vertical axis measures the _______________.
3.
In a time-domain plot, the vertical axis measures the _______________.
4.
If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what