Digital Communication 80 Marks Sample Test Paper

1. Sample Question Paper - I
Course Name : Electronics Engineering Group
Course Code : ET/EN/EX/EJ/IE/IS/IC/DE/EV/MU/IU/ED/EI 9122
Semester : Fifth
Title of Subject : Digital Communication
Marks : 80 Time: 3 hour
Instructions:
1. All questions are compulsory.
2. Illustrate your answers with neat sketches wherever necessary.
3. Figures to the right indicate full marks.
4. Assume suitable data if necessary.
5. Preferably, write the answers in sequential order.
Q.1. Attempt any four of the following 16 Marks
i) Define channel capacity and give the significance of the factors.
ii) State the advantages of pulse modulation over continous wave modulation.
iii) State the Bandwidth for the following and comment-
a) QPSK
b) DPSK
c) QAM
iv) Define Baud rate and Bit rate .Compare both with suitable example.
v) Describe WDM in detail.
vi) State applications of s.s modulation (any four).
Q.2. Attempt any three of the following 12 Marks
i) Draw labelled sketch for PWM and explain with waveforms.
ii) Illustrate how PPM is obtained from PWM ?
iii) Draw the following data format for the given bit stream-1100010
a) Polar NRZ
b) Unipolar RZ
c) Mnchester
d) AMI.
iv) How TDMA system is used in satellite communication?
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2. Q.3. Attempt any three of the following 12 Marks
i) Distinguish between Baseband and Passband transmission.
ii) Describe QAM technique.
iii) Define ASK and FSK with waveforms.
iv) Define channel noise and state its effects.
Q.4. Attempt any two of the following 16 Marks
i) Draw labeled sketch for PPM. Explain it with waveforms.
ii) Describe TDM and FDM techniques.
iii) Describe DSSS system in detail.
Q.5. Attempt any two of the following 12 Marks
i) Draw labeled sketch for PCM and explain with waveforms.
ii) Describe QPSK transmitter and receiver.
iii) Distinguish between DPSK, BPSK and QPSK.
Q.6. Attempt any two of the following 12 Marks
i) Describe with example Baud rate code and EBCDIC code.
ii) Generator matrix for (7,4) is given below-
G= 1000:101
0100:111
0010:110
0001:011
a) Find all code vectors
b) Find polarity check matrix.
iii) Compare between DSSS and FHSS technique.
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