Digital Signal Processing Reference
In-Depth Information
m
(
t
)
5
20
10
0
10
20
t
( s)
5
Figure P6.31
6.32.
The triangular pulse waveform shown in Figure P6.31 is used to modulate a carrier sig-
nal
cos(10
6
pt)
by DSB/WC-AM modulation techniques with
k
a
= 0.05.
(a)
Sketch the resulting modulated signal,
(b)
Derive the frequency spectrum of the modulated signal.
(c)
Sketch the frequency spectrum,
s(t) = m(t)c(t).
S(v).
6.33.
The signal with the frequency spectrum shown in Figure P6.33(a) is used to pulse-
amplitude modulate the signal shown in Figure P6.33(b). Sketch the modulated
signal's magnitude frequency spectrum.
p(t)
M
( )
p
(
t
)
4
1
500
0
500
0
0.1
1.0 1.1
2.0
2.1
3.0 3.1
t
(ms)
(a)
(b)
Figure P6.33
6.34.
The system shown in Figure P6.34 is used, with a sampling rate of 2.4 MHz, to time-
division multiplex a number of pulse-amplitude-modulated signals.
(a)
If the pulses are
8 ms
in duration, how many PAM signals can be multiplexed?
(b)
If the pulses are
8 ms
in duration, what is the first-null bandwidth of the TDM
signal?
PAM signals
s
1
(
t
)
s
2
(
t
)
Time-division
multiplexer
s
3
(
t
)
TDM signal
s
n
(
t
)
Figure P6.34
6.35.
Sketch the frequency spectrum of the flat-topped PAM signal resulting from modulat-
ing the signal
p(t)
shown in Figure P6.33(b) with a signal
m(t)
with the frequency spec-
trum shown in Figure P6.33(a).
