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Previous Year Exam Questions for Communication Engineering - CE of 2018 - CEC by Bput Toppers

  • Communication Engineering - CE
  • 2018
  • PYQ
  • Biju Patnaik University of Technology Rourkela Odisha - BPUT
  • Information Technology Engineering
  • B.Tech
  • 1172 Views
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Registration No : Total Number of Pages : 02 B.Tech. PCEE4304 6th Semester Back Examination 2017-18 COMMUNICATION ENGINEERING BRANCH : IT Time : 3 Hours Max Marks : 70 Q.CODE : C420 Answer Question No.1 which is compulsory and any five from the rest. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) g) h) i) j) Q2 a) b) Q3 a) b) Answer the following questions : Write the frequency range of shortwave radio and at least four of its applications. Illustrates the signal attenuation in dB/mile due to precipitation for frequencies in the range of 10–100GHz and derive at least one conclusion. Express the relation between x(t),V(t) and Θ(t) to draw the envelopeandphaseofa bandpass signal. Show that Rayleigh’s relation for periodic signals is a special case of the Parseval’s relation for Fourier series. Which modulation techniques are used for transmission of picture and speech signals in commercial TV broadcasting in India and why? A 3 GHz carrier is DSB-SC modulated by a low-pass message signal with maximum frequency of 2 MHz. The resultant signal is to be ideally sampled. What will be the minimum frequency of the sampling impulse train? A super heterodyne radio receiver with an intermediate frequency of 455 KHz is tuned to a station operating at 1100 KHz. Calculate the image frequency. The messages band limited to W, 2W, 3W and 4W respectively are to be multiplexed using TDM. What is the minimum bandwidth required to transmit this TDM signal. Consider a linear DM system designed to accommodate analog message signals limited to bandwidth of 3.2 kHz. A sinusoidal test signal of amplitude Am = 1 V and frequency fm = 800 Hz is applied to system. The sampling rate of the system is 64 kHz. Find the granular noise power for the system A binary channel with capacity 46 k bits/sec is available for PCM voice transmission. If signal is band limited to 4.2 kHz, then find the appropriate values of quantizing level and the sampling frequency. (2 x 10) Discuss the mathematical models for communication channels by referring appropriate block diagrams. Show that for all periodic physical signals that havefinite power, the coefficientsof the Fourier series expansion extend to zero asn→∞ (5) Let X(f) ≡0 for|f|≥W. Let x(t)be sampled at multiples of some basic sampling intervalTs, where Ts≤ , to get the sequence { ( )} ∞ ∞ Then reconstruct the original signalx(t)from the sampled values by using the reconstruction formula. Determine the Fourier transform of the following signals (αis positive). (5) ∝ (5) (5)

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Q4 a) b) Q5 a) b) Q6 a) b) Q7 Q8 a) b) c) d) Derive the power content for SSB and VSB signal. Write their significance with respect to real life broadcasting scenario. Why a balance discriminator used in FM demodulation? Explain the balanced discriminator with it’s corresponding frequency response using suitable diagram. (5) Using suitable diagram / reasons answer the following questions:i) What is interlaced scanning pattern? ii) What is the maximum bandwidth of the video signal and why it is as such? iii) What is the total channel bandwidthrequired to transmit the video and audio signals and why? A SSB AM signal is generated by modulating an 500-kHz carrier by the signal m(t)=cos 1000πt +2 sin 1000πt. The amplitude of the carrier is Ac =50. i) Determine the signal ( ). ii) Determine the (time domain) expression for the lower sideband of the SSB AM signal. iii) Determine the magnitude spectrum of the lower sideband SSB signal.. (5) What is cross talk? Why it is appeared in PAM? Explain cross talk in PAM due to HF and LF limitation of the channels? Which of this affects more than one channel and why? Find the transmission rates of T1, T2, T3, T4 & T5 carrier systems. (5) In a single integration DM system, the voice signal is sampled at a rate of 64 kHz.The maximum signal amplitude is 1. i) Determine the minimum value of the step size of the modulator to avoid slope overload. ii) Determine the granular noise power, if the voice signal has bandwidth of 4 kHz. iii) Determine the SNR of the system, assuming the voice signal to be sinusoidal, with rms bandwidth of1.3 kHz. iv) Determinehow many similar voice channels can be transmitted over the same communication link for maximum utilization of the link under an acceptable level of SNR. (10) Write short answer on any TWO : Performance comparison of binary and S-ary system. Line codes. Super-heterodyne FM radio receiver. Properties of Fourier transform. (5) (5) (5) (5 x 2)

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