19-01-2016, 04:36 PM
B.Tech. (EC) Finat Year, VII Semester, Session 2013-14
First mid Term Exam
Time -1&1/2 hrs Satellite Communication (ECE-407) Max Marks:20
Notes
l. Answer four questions from Section A, any two from Section B and any two from Section C.
2. All parts of a question (a, b, etc.) should be answered at one place.
3. Answer should be brief and to-the-point and be supplemented with neat sketches.
4. Any missing or wrong data may be assumed suitably giving proper justificatiou.
5. Figures on th. right-hand sitle margin indicate the marks.
6. Asiume the average radius of the earth is 6378.137 km and Kepler's constant has the value 3.986004418 x
los kmr/s2.
SECTION- A
Note: Answer anY FOUR questions. 4xl=4
I. Write the frequency range in GHz for uplink & downlink for C & Ku bands for satellite communication'
II. Write the expressions for lirrear velocity & average areal velocity of a satellite giving the meaning of each term.
llt. A satellite system has uplink CNR as 20 dB and downlink CNR as 30 dB then overall CNR is
IV: If the power output of the TWTA of a satellite is 9 dBW operating with an output backoff of 5 dB, then the
power output ir; W of tlte 'l'WTn rccluircd fbr lirll saturated EIRP is
V. Wr-ite tfte FltlSS lbrrnula irrcor'1tt-u'itl.rttg :iystcnl losscs givittg tltc tttcrtttitrll ol u.tcir lct tri.
VI. If an eafth station is in the nofthern hemisphere with satellite to the SW of the earth station, then the azimutlt
angle is given by
SECTION- B
Note: Answer any TWO Questions
l. Define the following terms.
(a) Declination (b) Right Ascension
(d) Argument of pei'igce west (e) Elevation Angle
3+3:6
© Inclination
.(l) Azimuth'Angle
ll.
III.
Write the conditions for a satellite to be a Geostationary. Calculate the altitude & linear velocity of a GEO -
stationary satellite.
Explain the technique of placing the satellite in GEO orbit with the help of AKM with neat sketch
Page 1 of 2
SECTION- C
Note: Answer any TWO questions. 5+5:10
I. What do you mean by ,the transponder' as applied to a communications satellite? Differentiate between base
band & bent pipe transponders.Draw the block diagram of singte conversion type transponder at C band
mentioning the value of fiequency at the input & output of each block.
Il. A C-band earth station has an antenna with a transmit gain of 54 dB. The transmitter otltput power is set to
100 W at a frequency of 6.100 GHz. The signal is received by a satellite at a distance of 37,500 km by an
unt.nnu with a gain of 26 dB. The signal is then routed to a transponder with a noise tempemture of 500 K, a
bandwidth of 36 MHz; and a gairr of I l0 dB' Calculate
a) The path loss at 6.1 GHz
b) Calculate the power at the output port (sornetimes called the output waveguide flange) of the satellite
antenna, in dBW.
c) calculate tlre noisc power at tlre transponder input. in dBW, irr a bandwidth of 36 Ml-lz'
d) ('alcttllttc tltc C/N t'ittio, ilt dl]' irt llrc trartspottclcr
c) calculatc thc carricr powcf, ill dllw attd irt watts, at the tratrspondcr output'
f ll. A 4 Gtlzreceiver has the fbllowing gains and noise temperatures:
'l',,, 25 l(, l'ru'"50 K' 'l',"'6(X)K' 'l'rt" l l(X)K' (ix1'=25 dB' Grr':30 dl]
,,1 ('lrlctrlrrtc tlrc systerrr rrtrist'lcrrrpclirttc lvltcrt tltc ttrixcr ltas a gain ol'0 dl]'
t,) ltccalcslatq thc systcrn rroisc tcrrrl'rcralut'c wltct'l thc tttixcr has a loss ol' l0 dB'
c) How cap t5e terlpclattrrc ol-ttrc rcceiver be nrinimized wltett the mixer has a loss of l0 dB ?