DipIETE – ET (OLD SCHEME)

 

Code: DE17                                Subject: ELEMENTS OF SATELLITE COMMUNICATION

Flowchart: Alternate Process: JUNE 2010Time: 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.       Satellite transponders _______________.

 

                   (A) use a single frequency for reception and retransmission of                 information to and from earth

                   (B) use a lower frequency for reception and a higher frequency for         retransmission     

(C)    use a higher frequency for reception and a lower frequency for   retransmission

(D)  use S band for reception and X band frequency for transmission                               

 

b.      The orbital velocity of the satellite

 

(A)    is directly proportional to its distance from earth’s surface

(B)    is inversely proportional to square root of its distance from earth’s center.

(C)    depends upon the thrust with which it is launched

(D)    is continuously changing as the satellite moves                                                           

            

             c.   The angular velocity () of a satellite at a height (H) from the surface of the earth with a mean radius of R is given by 

                  

(A)                         (B) 

(C)                        (D) 

 

             d.   Satellite S1 and S2 are orbiting in two different equatorial circular orbits. The radius of S1 orbit is four times the radius of S2 orbit. The orbital period of S1 orbit will therefore be 

 

                   (A)  Four times the orbital period of S2                                                                            

                   (B)  Eight times the orbital period of S2

                   (C) Two times the orbital period of S2

                   (D) Same as the orbital period of S2

       


 

             e.   The satellite tracking stations are placed in remote areas in order to minimize the effect of

                  

(A)     Solar noise                                   (B)  Man made noise

(C)  Cosmic noise                                (D) Thermal noise

 

             f.    The range of Ku Band is 

 

(A)     24 – 36 GHz                                (B)  12 – 18 GHz

(C)  16 – 24 GHz                                (D   24 – 40 GHz

 

             g.   In broadcast satellites, the high power transmitters are based on

 

(A)     TWT                                           (B)  LASERS

(C)  MASERS                                    (D) MOSFETS

       

             h.   SCPC essentially is a 

 

(A)    Non-multiplexed low capacity TDMA

(B)    Non-multiplexed low capacity FDMA

(C)    Multiplexed low capacity TDMA

(D)    Multiplexed low capacity FDMA 

 

             i.    Digital DBS-TV transmission uses a transmitted symbol rate of 

 

(A)  10 Mbits/sec using QPSK            (B) 20 Mbits/sec using QPSK

(C) 10 Mbits/sec using  PSK               (D) 20 Mbits/sec using  PSK

 

             j.    Each INSAT – I satellites has 

 

(A) Three TV broadcast transponders operating in S-band uplink and C-band                                                                                                                                                                                                                                                                                                                                                                                                      downlink                                           

(B) Three TV broadcast transponders operating in C-band uplink and S-band        downlink

(C) Two TV broadcast transponders operating in S-band uplink and C-band        downlink

(D) Two TV broadcast transponders operating in C-band uplink and S-band        downlink          

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   Derive the expressions for C/N and G/T ratios and explain their significance.           .           (8)       

       

             b.   In a satellite link, the antenna of the earth station used to receive a signal at 4150 MHz, has diameter of 30 m and an overall efficiency of 68%.The system noise temperature is 79 K when the antenna points at the satellite at an elevation angle of . Find the earth station G/T ratio.                   (8)

 

  Q.3     a.   Explain analog base band signal & explain SCPC system.                                   (8)

 

             b.   Explain Quadrature Phase Shift Keying system.                                                  (8)

 

  Q.4     a.   Explain simple Direct Sequence Spread Spectrum Modulation and PN

                   sequences.                                                                                                       (10)          

 

b.   Explain Demand Assignment Control.                                                                (6)

 

  Q.5     a.   Discuss the Satellite location with respect to earth.                                              (8)

 

             b.   Explain the terms                                                                                                (8)

                   (i)  Look angles and

                   (ii) Station Keeping                              .                                                                 

 

  Q.6     a.   Explain, with a block diagram the operation of Repeater/Transponder.                (8)

       

             b.   Explain how altitude and orbital control is carried in a satellite system.                 (8)

 

  Q.7     a.   Explain, with neat block diagrams the satellite earth station’s

                   (i)  Transmitter and

                   (ii)  Receiver                                        .                                                          (10)   

 

             b.   Determine the orbital velocity of a satellite moving in a circular orbit at a height of 150 km above the surface of earth given that gravitation constant, G = 6.67 1011 N-m2/kg2, mass of earth M = 5.98 1024 kg, and radius of earth R = 6370 km                .                                                             (6)

                  

  Q.8     a.   Explain basic DBS-TV system and mention the features and specifications of a Typical DBS-TV satellite system.                                                (9)

 

             b.   Explain Network Architecture of a Cable TV system                                          (7)

 

  Q.9           Explain the following;                                                                                  (2  8)

 

(i)         Weather Forecasting with Satellite.

(ii)       INSAT-I Satellite Series