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Department of Electrical and Computer Engineering Introductions O Communication Systems

This document is a quiz for a communications systems course covering topics in amplitude modulation (AM). It contains 10 multiple choice questions testing students' understanding of key AM concepts like modulation index, carrier power, sideband frequencies, and bandwidth calculations. The quiz asks students to identify the carrier frequency, modulation indices, bandwidth, and power distributions for various AM signals described in the questions.

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87 views2 pages

Department of Electrical and Computer Engineering Introductions O Communication Systems

This document is a quiz for a communications systems course covering topics in amplitude modulation (AM). It contains 10 multiple choice questions testing students' understanding of key AM concepts like modulation index, carrier power, sideband frequencies, and bandwidth calculations. The quiz asks students to identify the carrier frequency, modulation indices, bandwidth, and power distributions for various AM signals described in the questions.

Uploaded by

RoopaNarsi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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WOLAITA SODO UNIVERSITY

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING


III YEAR ELECTRICAL AND COMPUTER ENGINEERING
INTRODUCTIONS O COMMUNICATION SYSTEMS
QUIZ-2-EXAMINATION - 2017

Name Of the Student : ID No : Section:

Max Marks : 1/2 x10 = 5Marks Time : 30 Mins Date : 11-4-2017


Choose the Correct Answer from the given Options 1/2X1 = 5 Marks
1. Amplitude modulation is [ ]
A. Change in amplitude of the carrier according to modulating signal
B. Change in frequency of the carrier according to modulating signal
C. Change in amplitude of the modulating signal according to carrier signal
D. Change in amplitude of the carrier according to modulating signal frequency [ ]
2. The AM spectrum consists of
A. Carrier frequency B. Upper side band frequency
C. Lower side band frequency D. All of the above
3. With AM which of the following conveys no information? [ ]
A. lower side band B. upper sideband
C. both sidebands D. carrier
4. What is the carrier frequency in an AM wave when its highest frequency component is 850Hz and the bandwidth of the signal is
50Hz? [ ]
A. 80 Hz B. 695 Hz
C. 625 Hz D. 825 Hz
5. In amplitude modulation, how much of the transmitted power is in the carrier? [ ]
A.one-half B. three-quarters
C.one-third D. two-thirds
6. An AM transmitter has an antenna current changing from 5 A un modulated to 5.8 A. What is the percentage of modulation?
[ ]
A. 38.8% B. 83.14%
C. 46.8% D. 25.2%
7. An AM signal has a total power of 48 Watts with 45% modulation. Calculate the power in the carrier and the sidebands.
[ ]
A. 39.59 W, 4.505 W B. 40.59 W, 4.205 W
C. 43.59 W, 2.205 W D. 31.59 W, 8.205 W
8. If an AM signal is represented by s(t) = (10 + 2cos( 2 * 8 * 103 t) ) * cos (2 * 1.6 * 106 t) volts [ ]
i) Calculate the values of the frequencies of carrier and modulating signals.
ii) Calculate the value of modulation index.
iii) Calculate the value of bandwidth of this signal.
A. 1.6 MHz and 8 KHz, 0.6, 16 MHz B. 1.9 MHz and 18 KHz, 0.2, 16 KHz
C. 2.4 MHz and 18 KHz, 0.2, 16 KHz D. 1.6 MHz and 8 KHz, 0.2, 16 KHz
9. Calculate the total modulation Index when a carrier wave is being modulated by two modulating signals with modulation indices
0.8 and 0.3. [ ]
A. 0.8544 B. 0.6788
C. 0.9999 D. 0.5545
10. An AM broadcast station transmits modulating frequencies up to 6 kHz. If the AM station is transmitting on a frequency of

894 kHz, the values for maximum and minimum upper and lower sidebands and the total bandwidth occupied by the AM station
are: [ ]
A. 900 KHz, 888 KHz, 12 KHz B. 894 KHz, 884 KHz, 12 KHz
C. 894 KHz, 888 KHz, 6 KHz D. 900 KHz, 888 KHz, 6 KHz

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