DipIETE – ET (OLD SCHEME)

Code: DE17                                Subject: ELEMENTS OF SATELLITE COMMUNICATION

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or the best alternative in the following:                                 (2 10)

a. ITU has divided the world into

(A)  3 regions                                      (B)  4 regions

(C)   2 regions                                     (D)  6 regions                                                       

b. The system which collects data from sensors of space craft and sends to the controlling earth station is called _________

(A) Tracking system                           (B)  Telemetry system

(C)  Power system                               (D)  AOCS system

             c.   The energy per bit for QPSK is  

(A) (B)

(C) (D)

             d.   The farthiest distance that a satellite orbit reaches from the earth surface is called 

                   (A)  Apogee                                        (B)  Perigee

(C)  Prograde                                      (D)  Retrograde

             e.   The height of the geostationary orbit from the earth’s surface is

(A) 900 Kms                                     (B)  1800 Kms

(C)  42500 Kms (D)  35860 Kms

             f.    Long distance communication system via satellite in Ku band uses frequencies in the range of 

(A) 3-6 GHz                                      (B)  11-14 GHz

(C)  100-200 GHz                              (D)  3-6 MHz

             g.   The multiple satellite access system which suffers from the presence of intermodulation products in

(A) TDMA                                        (B)  FDMA

(C)  CDMA                                        (D)  DAMA

             h.   The video carrier frequency (in MHz) usually employed for the T-9 cable TV channel is around 

(A) 7                                                  (B) 25

(C)  19                                                (D) 13

             i.    The satellite orbit is termed as a retrograde orbit when its angle of inclination 

(A)  becomes (B) exceeds

(C) zero                                              (D) becomes

             j.    Multipoint communication capabilities are more in 

(A) Fiber optics                                   (B) Satellite

(C) Ethernet                                        (D) Telephones

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   How many frequency bands have been allocated for use with satellite communications and which are they?  Illustrate in the form of table the frequency allocations for mobile satellite service. (8)

             b.   Draw and explain the switched star topology used in cable TV system.                (8)

Q.3     a.   Explain the importance of G/T ratio in satellite link design.                                   (8)

             b.   What do you mean by TDMA?  Describe TDMA frame structure.                     (8)

Q.4     a.   What is QPSK?  Describe generation of QPSK.                                                (8)

b.   Draw and explain the block diagram of earth station transmitter.                          (8)

Q.5     a.   Explain how a satellite is placed in geostationary orbit.                                        (8)

b.   What are altitude and orbit control sub-system?  Explain how do they perform their functions?                                                                   (8)

  Q.6     a. What is meant by station keeping of a satellite?  Explain its significance and methods to achieve it.                                                              (8)

             b.   Describe the important features of INSAT-I satellite.                                          (8)

Q.7     a.   Explain S/N and C/N in FM.                                                                            (8)

             b.   Explain the following terms:

                   (i)   Look angles                                  (ii)   Synchronous orbit.                           (8)

Q.8     a.   Explain in detail why 6/4 GHz communication is used in satellite communication systems.                 (8)

             b.   Derive the link equation as referred to a geostationary satellites.                          (8)

Q.9           Write short notes on any TWO of following:-                                        (8 2=16)

(i) Direct broadcast satellite.

(ii) Satellite transponder.

(iii) Data broad casting using satellites.