Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 5th Semester (Fifth Semester) 2017-2018 NEC502 Principles Of Communication Question Paper
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BTECH
(SEM V) THEORY EXAMINATION 2017-18
PRINCIPLES OF COMMUNICATION
Time: 3 Hours T 0tal Marks: 100
Notes: Attempt all Sections. Assume any missing data
M
Q1. Attempt all parts in brief. (2*10=20 )
a) What is baseband signal?
b) Draw block diagram of analog communication System.
c) What VSB Signali How it is used for reduction of Bandwidth.
(1) Draw phasor diagram for AM system along with its application.
e) What is Modulation? Why it is required.
t) Why is Line Coding required in Communication System?
g) What is Quantizer? What role does it play in Digital Transmission?
h) List Comparison between Narrowband & Wideband FMi
i) What is White Noise? Draw its Spectral Density Curve.
j) What is Noise Figure? List Sources of Noise.
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Q2. Attempt any three question .All question carry equal marks (10*3=30)
a) Calculate the percentage saving when the carrier and one of the sideband are suppressed in an AM
wave modulated to a depth of i) 100% ii) 75%.
b) Draw & Explain the block diagram of Phase shift method for generating the SSB Signal.
c) Explain modulation and demodulation of PWM system using suitable waveform?
d) What do you mean by Noise? Show the effect of certain types of filter on the noise What is slope
overload distortion and granular or Idle noise
e) What is Differential Pulse Code Modulation? Explain working of DPCM with a proper block
Diagram.
Q3. Attempt any one question .All question carry equal marks (10*1=10)
a) The ef?ciency 1] of ordinary AM is de?ned as the percentage of the total power carried by the
sidebands, that is
n = P s/ P t
Where P5 is the power carried by the sidebands and Pt is the total power of the AM signal.
i) Find 11 for m3 = 05 (50% modulation)
ii) Show that for a single tone AM 11 max is 33% at ma=1i
b) Assuming sinusoidal modulation prove that AM system with envelop detection the output signal to
noise ratio(SNR) is given by
(S/N) = (m2/2+m2) 7
Where In is modulation index for AM and y=(Si/ nfm)
Q4. Attempt any one question A? question carry equal marks (10*1=10)
a) In an F M system a 7 kHz modulating signal modulates 107.6Mhz carrier wave,so that the frequency
deviation is 50Khz.Determine
i) Carrier Swing in the F M signal and modulation index.
ii) The Highest and lowest frequency attained by the F M Signal
b) Derive the expression for Narrowband F M signal and Wide Band F M. Explain advantage of
Modulation Index
Q5. Attempt any one question A? question carry equal marks (10*1=10)
a) A PCM system uses a uniform Quantizer followed by a 7-bit Binary encoderi The bit rate of the
System is equal to 50 x 106 bits/seci Calculate
i) What is the maximum message signal bandwidth for which the system operates satisfactory?
ii) Calculate the output signal to noise ratio when full load sinusoidal modulating wave
of frequency 1Mhz is applied to the input
b) Explain ?at top sampling in detail?
Q6. Attempt any one question A? question carry equal marks (10*1=10)
a) Explain working of Adaptive Delta modulation with a proper block Diagram
2
b) Show that maximum quantization error in PCM is given by E
Q7. Attempt any one question A? question carry equal marks (10*1=10)
a) For a given sequence 1011001011 construct Unipolar NRZ, Unipolar RZ bipolar NRZ, bipolar RZ,
Alternate Mark Inversion (AMI), and Manchester format?
b) What is pre-emphasis and de-emphasis and how SNR improves by using pre-emphasis and de-
emphasis? F ind out the figure of merit in SSB?SC.
This post was last modified on 29 January 2020