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Code No: N0406
Set No. 1
IV B.Tech I Semester Regular Examinations, November 2009
SATELLITE COMMUNICATIONS
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. What is Van Allen Belt? Mention its relation with Satellite
Communication. [16]
2. Discuss in detail the effects of Earth Gravitational Force on
Satellite.[16]
3. (a) Discuss the orbit control system in brief.
(b) Draw the simplified block diagram of a satellite subsystem for 6/4
GHz band.
[
8
+
8
]
4. (a) A Satellite receiving system consists of an aerial waveguide runs
from the aerial
to the input of the first amplifier, low noise first amplifier and
succeeding
stages. Derive an expression for the system noise temperature in
terms of
standard parameters.
(b) In a satellite link the propagation loss is 200dB, Other losses are
3dB. The
receiver G/T is 11dB/K and the EIRP is 45dBW. Calculate the
received C/N
for an FDM base band consisting of 96 voice channels.
[8+8]
5. What is meant by TDMA frame acquisition and frame synchronization?
What is
frame delay? How does it help in carrying out TDMA frame acquisition
and frame
synchronization techniques?[16]
6. Explain to why it is necessary to have frequency coordination among
earth stations
themselves and earth station-terrestrial microwave link? Discuss the
techniques to
achieve them?[16]
7. Explain the main elements of the GSM network.[16]
8. (a) What is the need of timing accuracy in GPS?
(b) How accuracy is provided in GPS receiver?[8+8]
Code No: N0406
Set No. 2
IV B.Tech I Semester Regular Examinations, November 2009
SATELLITE COMMUNICATIONS
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) Write a detailed summary of European expandable launch vehicles.
(b) Discuss in detail the various operational centers of ISRO and their
Responsibilities.[8+8]
2. (a) Compare the three types of Satellite Orbits.
(b) State Kepler’s Laws and prove that the Satellite Orbit is an
ellipse.[8+8]
3. (a) List the various satellite subsystems and state their purpose and
principal
parameter that characterize them quantatively.
(b) Explain the following:
i. Telemetry
ii. Tracking and Command.[8+4+4]
4. (a) Explain down link design objectives of a satellite communication
system and
hence give the down link design of Intel Sat IV-A Satellite.
(b) A Satellite carrying an 11.7 GHz signal transmitter is located at
40,000Km
from an earth station. The transmitting antenna with gain 17dB
radiates a
power of 200mW towards earth station. The diameter of the
receiving antenna
is 10 meters and the aperture efficiency is 50 percent:
i. Calculate the receiving antenna gain.
ii. The earth station G/T
iii. The C/N in a 100 Hz noise bandwidth. If the overall system
noise temperature is 12500 K.[8+8]
5. (a) Explain structure of an Intelsat traffic data burst?
(b) A TDMA network of five earth stations shares a single transponder
equally.
The frame duration is 2.0ms, the preamble time per station is
20microsec,
and guard band of 5microsec are used between bursts.
Transmission bursts
are QPSK at 30Mbaud.[6+10]
6. What are the main considerations in the design of the earth station?
With the
help of block diagram, discuss the operation of atypical large earth
Station. How
this configuration is is different from that of very small aperture
techniques? State
reasons for this difference?[16]
7. Explain the frequency band for LEO satellite systems.[16]
8. Explain in details about GPS position location principles.[16]
Code No: N0406
Set No. 3
IV B.Tech I Semester Regular Examinations, November 2009
SATELLITE COMMUNICATIONS
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. Discuss in detail the Design Consideration of a Satellite Communication
Systems.
2. (a) Explain about Expendable launch vehicle(ELVs)
(b) An Low earth orbit satellite is in circular polar orbit with an altitude
of 1000
km. A Transmitter on the satellite has a frequency of 2.65 G Hz.
Find:
i. The velocity of the satellite in orbit
ii. The component of velocity toward an observer at an earth
station as the
satellite appears over the horizon, for an observer who is in
the plane of
[
1
6
]
the satellite orbit.
iii. The Doppler Shift of the received signal at an earth station.
iv. Find also the Doppler shift for a satellite signal (transmitted by
Ka band
transmitter at 20.0 GHz). When it is received by the same
observer.[8+8]
3. Write in detail about Altitude and orbit control systems (AOCS).[16]
4. Explain in detail the losses that occur during propagation of EM wave
from earth
station to satellite and vice versa. In what way they help in satellite
communication
link design.[16]
5. (a) Define Bits, Symbols and channels in TDMA.
(b) Explain TDMA frame structure.[3+13]
6. Explain what is meant by single-entry interference. Explain why it is the
radiation
pattern if the earth station antenna, not the satellite antennas, which
governs the
level of interference?[16]
7. Explain the coverage of an equatorial and Inclined orbit of LEO.[16]
8. Write about the satellite signal Acquisition?[16]
Code No: N0406
Set No. 4
IV B.Tech I Semester Regular Examinations, November 2009
SATELLITE COMMUNICATIONS
( Common to Electronics & Communication Engineering and Electronics &
Telematics)
Time: 3 hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) Prove that three Communication Satellites would be sufficient for
covering the
globe.
(b) Write a summary of US expandable launch services.[8+8]
2. (a) The Semi major and Semi minor axis of an Elliptical Satellite Orbit
are 20,000
Km and 16,000Km respectively. Determine the apogee and
perigee distances.
(b) A Geosynchronous Satellite moving in an equatorial circular orbit
at a height
of 35000 Km above the surface of the Earth gets inclined at an
angle of 20.
Calculate the maximum deviation in latitude and also maximum
deviation in
longitude. Determine the maximum displacements in Km caused
by latitude
and longitude displacements..[8+8]
3. Describe the equipment sections making up a Transponder
Channel[16]
4. (a) Discuss the uplink design.
(b) A Transponder of a Ku band satellite has linear gain of 127 dB and
a nominal
output power at saturation of 5W. The satellite’s 14GHz receiving
antenna
has a gain of 26 dB on axis and the beam covers western Europe.
Calculate
the power output of an uplink transmitter that gives an output
power of 1W
from the satellite transponder at frequency of 14.45GHz. when
the earth station antenna has a gain of 50 dB and there is a 1.5 dB loss in the
waveguide
run between the transmitter and antenna.
Assume that the atmosphere introduces a loss of 0.5dB under
clear sky conditions and that the earth station is located on the -2dB contour of
the satellite?s
receiving antenna. If the rain in the path causes attenuation of 7
dB for 0.01%
of the year. What output power rating is required for the
transmitter to guarantee that a 1 W output can be obtained from the satellite
transponder for
99.9% of the year if the uplink power control is used.
[8+8]
5. (a) Write the differences between TDM and TDMA?
(b) Illustrate the TDMA with three earth stations.[4+12]
6. (a) Discuss the receiver working in Earth station with suitable
diagrams?
(b) Explain various LNA’s used?[8+8]
7. (a) What are the two approaches used to provide real-time connection
between
LEO satellite and MCS?
(b) Define dwell time? What are elliptical orbits?
(c) Explain the store and forward concept.[4+6+6]
8. Explain how GPS satellite use direct sequence spread spectrum?