1
GATE ECE 2004
+1
-0.3
An AM signal is detected using an envelope detector. The carrier frequency and modulating signal frequency are 1 MHz and 2 KHz respectively. An appropriate value for the time constant of the envelope detector is
A
500 µsec
B
20 µsec
C
0.2 µsec
D
1 µsec
2
GATE ECE 2004
+1
-0.3
An AM signal and a narrow-band FM signal with identical carriers, modulating signals and modulation indices of 0.1 are added together. The resultant signal can be closely approximated by
A
B
SSB with carrier
C
DSB-SC
D
SSB without carrier
3
GATE ECE 2002
+1
-0.3
A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave of period 100 µsec. Which of the following frequencies will NOT be present in the modulated signal?
A
990 kHz
B
1010 kHz
C
1020 kHz
D
1030 kHz
4
GATE ECE 1999
+1
-0.3
A modulated signal is given by, $$s\left(t\right)=m_1\left(t\right)\cos\left(2{\mathrm{πf}}_\mathrm c\mathrm t\right)\;+m_2\left(t\right)\sin\left(2{\mathrm{πf}}_\mathrm c\mathrm t\right)$$, where the baseband signal m1(t) and m2(t) have bandwidths of 10 kHz and 15 kHz, respectively. The bandwidth of the modulated signal, in kHz, is
A
10 kHz
B
15 kHz
C
25 kHz
D
30 kHz
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