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# Bengal Engineering and Science University 2006 B.E Computer Science and Engineering Satellite Communications - Question Paper

Friday, 18 January 2013 01:15Web

the ques. paper is with the attachment.

Ex/BESUS/ ETC-814/4/ 06

B.E. (CST, IT) Part-IV 8th Semester Examination, 2006

Satellite Communications

(Elective-III) (ETC-814/4)

Time: 3 hours    Full Marks : 100

Use separate answerscript for each half. Answer SIX questions, taking THREE from each half. Two marks are reserved for neatness in each half.

FIRST HALF

1. a) Mention some advantages of satellite communication over terrestrial communication.

Why specifically 6 GHz used for uplink and 4 GHz for downlink.

Explain the basic differences between an active and passive satellite. Whether can a passive satellite be used for communication?

What is Van Allen belt?    [4+4+6+2J

d

2. a b

c

d

3. a

b

c

Name and explain the orbital parameters required to determine a satellite orbit.

What is meant by look angles? Explain them with reference to a geo stationary satellite and the earth station.

Mention the effect of gravitational force due to sun and moon on the orbital motion of a satellite.

What do you mean by the sun-transit outage?    14+6+4+2]

With the help of a block diagram explain telemetry, tracking and command (TT&C) sub-system of a satellite.

What is a transponder? Mention the advantages of a double conversion transponder over its single conversion counterpart.

What do you mean by station keeping of a satellite?    [8+6+2]

Mention the factors that affect the link design of a satellite. How is the uplink design is different from than the downlink design? Why is design of downlink more critical than that of uplink? Under what conditions dose a complete satellite link become downlink limited?

b) A satellite at a distance of 36,000 km from the surface of the earth radiates a power of 4 watts from art antenna of gain 15 dB. Find the flux density and power received by ah antenna of effective area 12m2. If the receiving antenna has a gain of 50 dB, then also calculate the received power. |(2+2+2+4)+6]

5.    a) How many types of earth stations are there? Write down the requirements

for the design of an earth station. Explain with a block diagram the working of receiver part of earth station.

b) With the help of a block diagram, briefly describe the functioning of the indoor receiving unit of a satellite TV receiving system intended for home reception.

|(2+2+6)+6|

SECOND HALF

6.    a) Explain what do you mean by a single access and a multiple access in relation

to satellite communication.

b)    What is burst? Explain the difference between the reference burst and traffic imrst of a IDMArfrarftes---

c)    Mention the differences between a pre assignment and demand assignment multiple access system.    |2+(2+6)+6|

7.    a) How many types of multiplexing are there in analog satellite communication

system? Which type of multiplexing is mostly used and why?

b)    With a neat schematic diagram explain how five 12 channel basic groups are multiplexed to form a supergroup.

c)    What do you mean by frequency reuse? Explain its application in analog satellite communication.    [(2+2)+6+(2+4)|

8.    a) With the help of a block diagram explain the operation of a digital modulator.

b)    What is symbol error rate? How is it different from bit error rate? How does it affect M-ary modulation?

c)    With the help of a block diagram briefly explain the function of a quadrature amplitude modulation (QAM).    |4+(2+2+2)+6|

9. a)    What is cyclic code? Mention its merit and demerits.

b)    What do you mean by automatic repeat request?

c)    How can the error detection technique be implemented over a satellite link?

d)    Write a short note on linear block coding.    |4+2+4+6|

10. Write short notes on any of the two special purpose communication satellite system:

a)    INMARSAT

b)    VSAT

c)    GPS

d)    IRIDIUM.    [8x2]