30-10-2012, 12:57 PM
IV B.Tech I Semester Regular Examinations - SATELLITE COMMUNICATIONS
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1. Explain in detail about India?s participation in other International communications
satellite systems. [16]
2. (a) What is transfer orbit and how is the orbit correction for the launch of satellite
at latitude other than equator is obtained? [6]
(b) Explain as to how satellite is placed into geostationary orbit from earth. [10]
3. (a) What is spin stabilization? Why is it necessary? Explain various effects that
is to be avoided and its remedial solution. [8]
(b) What is station keeping? Explain various methods of station keeping. [8]
4. Why lens antennas are preferred for satellite communication, explain in detail.
Explain the function of lens antenna. [16]
5. (a) What is the necessity of keeping front end of the satellite receiver at the
earth station in a helium-coolent: what is the range of temperature of the
preamplifier. [6]
(b) A transponder using the global beam, a typical output back off level of 3dB
with one access to that transponder so the radiated power from the transpon-
der is 5dBW giving EIRP of 21dBW. at 40,000kM. The threshold of C/N
is 11dB. Allowing a 7dB system margin. Calculate the diameter of the disk
antenna assuming an antenna efficiency of 65% . Assume any data missing.
[10]
6. (a) A 36 MHz satellite transponder is accessed by sequence-synchronous CDMA
users with bit rate 9.6 kbps. Gold sequences with a length of m=10 are used.
The link carrier-to-noise plus interference ratio is C/N = - 8 dB. Assume PSK
is used as carrier modulation. Find the number of users the transponder can
accommodate at Pe= 10−5
. [8]
(b) Consider a fast-hop FSK-FH-CDMA satellite channel where M hops are per-
formed per bit. The number of frequency slots in the channel is n. Find the
probability of intercepting k users in one bit interval. [8]
7. (a) What is Faraday rotation? How is it avoided in Satellite communication?
Explain which type of antenna is preferred to avoid it. [8]
(b) How do you select the site for earth station? Explain in detail.