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Department
ofElectrical Engineering
Faculty ofEngineering
& Applied Sciences
Riphah International Univ ersity
Midterm Examinations, Spring 2023 Semester
B.Sc. Electrical Eng ineering Program
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RIPHAH ;, >
INTl"RNATION AL
LIN\'flL<;ln' - v_
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CMS
Subject Na me : EE- CommunicationSystems
Marks 40 Time A ll owed : 2 Hours
Instruction s:
l. Kindly read thequestio n paper carefull ybefore solv in g it.
- You are not allo w ed to 'l'Tite anything on the Question Paper other than yo ur SAP num ber.
Q l:(CL0-1 )
(2+3+1+ marks!
Consider the baseband signal
m(t)= sin (J OOnt) sin (SOOrrt)
a) Sketch the spectrum of m(t).
b) Find and sketch the spectrumofDSB-SC signal 2m(t) cos ( nt).
c) Identify the upper sideband
(USB) and lo we r sideband (LSB) spectra and estimate the
bandwidth ofmodulated signa l.
d) Is it possible to demodulate the modulated signal? if yes which type of
dem odulator is
required and sketch the spectrum
ofdemodulated signa l.
Q 2: (CL0- )
(5+5+5 marks]
An AM mo dul ated signal is given by Xc(t) = (
+ 10cos(6 0001t t))cos(h/cl)
, where_/c = I OkHz.
a) What'st he p owe r transmitted for this AM signal? Wh at'sthe bandw idth?
Skecth the amplitude spectrum.
b)Ifthe same me ssage s igna l is transmitted using DSB, what
'sthe bandw idth and the po wer
transmitted? Sketch the amplitude spectrum.
c) If th e sam
e me ss age s igna l is transmitted using USB, what
'sthe bandw idth and the p ow er
transmitted? Sketch and anal yze the am plitu de spectrum a nd h ow it is di fferent fro m part (b)
Q3: (CL0-2)
[8+2+5 ma rks]
Consider the pe riodic triangle signal m(t) in the
figure.
Page 1 of 2
- Sketch the AM signal with extra carrier
for th e above periodic signal corresponding lo
modulati on indices
a.
μ=0.
b.
μ=
C.
μ=
d.
μ= 00
- How do you
compare
the case for
μ=
00
.
- Is it possible to demodulated the
m(t) when
μ=1, ifyes, draw the demodulator and
explain its working by sketching output signals at different points.
--End
ofPaper---------------------
Page
2 of 2
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lf
The real pa
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Midterm li::1111i11ntio
s, Spring 2023 Semester
B.Sc. Elect dea l Enginrcr
ing Proi{rani
Suhjl'CI Name: EE J 1 5-Linear Contrr;I System,
Tillie Allowed: 2 Hours
Question
No.1:(CLO1) Cl
Reii
rod ncc transfer functilrn Va(sJ ol'
the inverting a:11plifter sho w n in
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Question No.3:(CLO I)C
I 1o+s 1
Civen the de
se rvL>motor ~ml lo ad ~lw,,·n in
1 : igur e 3. Ass um! that the output
is the anguL1r
di ~p !aci.::ment ol'thc ,1rm,1tu
\·. l)o not ncgkt.:1 armature
inductant.:e.
Pa;;e 1 of 2
