Name of the College : Sphoorthy Engineering College
University : JNTUH
Department : Metallurgy And Material Technology
Subject Code/Name : 09A51701/ANALOG AND DIGITAL COMMUNICATIONS
Year : December 2011
Degree : B.Tech
Year/Sem : III/I
Website : sphoorthyengg.com
Document Type : Model Question Paper
Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/sphoorthyengg.com/4821-09A51701%20-%20ANALOG%20AND%20DIGITAL%20COMMUNICATIONS.pdf
Sphoorthy Analog & Digital Communications Question Paper
B. Tech III Year I Semester Examinations, December-2011
(ELECTRONICS AND TELEMATICS ENGINEERING)
Time: 3 hours
Max. Marks: 75
Related : Sphoorthy Mechanical Metallurgy B.Tech Question Paper : www.pdfquestion.in/4817.html
Model Questions
Answer any five questions :
All questions carry equal marks :
Set – I
1. a) Explain the need for modulation.
b) A lowpass signal x(t) having a bandwidth of 10 KHz is multiplied by coswct to produce xc(t). Find the value of fc so that the bandwidth of xc(t) is 1% of fc.[7+8]
2. a) State briefly the important criteria in the choice of intermediate frequency of a radio receiver.
b) A superhetrodyne receiver has an RF amplifier and an IF of 450 KHz is tuned to 600 KHz. Calculate the Q of the RF and mixer input tuned circuit both being the same, if the receiver’s image rejection is to be 120. [7+8]
3. a) What is meant by the following terms in connection with frequency modulation
i) modulation index ii) frequency deviation, and
iii) practical bandwidth
b) Explain the direct method of generation of FM and compare with indirect generation. [7+8]
4. a) Explain the operation of a PCM decoder. What is quantization noise? Derive the expression for SNR in PCM.
b) Explain the difference between slope overload noise and granular noise is delta modulator. [7+8]
5. a) With the help of block diagram explain baseband binary data transmission system.
b) What is the importance of baseband pulse shaping? [7+8]
6. a) Write the power spectral density of BPSK and QPSK signals and draw the power spectrum of each.
b) Compare the bandwidth of QPSK system with that of BPSK system. [7+8]
7. a) What is the mutual information? State the properties of mutual information.
b) Apply Shannon’s encoding procedure to the following message ensemble
8. a) Write the principle of convolutional codes.
b) Generate the CRC code for the data word of 110010101. The divisor is 10101. [7+8]
Set – II
R09Code No: 09A51701
SET-2
1. a) Compare noise in AM and DSBSC systems .
b) Derive an expression for (S/N)d for an AM System. [7+8]
2. a) Explain the generation of SSB using phase discrimination method.
b) In a broadcast superhetrodyne receiver having no RF amplifier, the loaded Q of the antenna coupling circuit (at the input to the mixer) is 100. If the IF is 455 KHz. Calculate the image frequency and its rejection ratio at 1000 KHz. [7+8]
3. a) Why is an FM system preferred over an AM System? Explain.
b) In a frequency modulating system, the frequency deviation constant is k = 1 KHz|V. A sinusoidal modulating signal of amplitude 15V and frequency 3KHz is applied. Calculate
i) The peak frequency deviation, and (b) the modulating index. [7+8]
4. a) What do you understand by PCM? How quantizing and coding is done?
b) Explain the operation of a delta modulation system. Explain a method of overcoming limitations of delta modulation. [7+8]
5. a) Explain the duobinary baseband PAM system.
b) What is the importance of Eye pattern? Explain. [7+8]
6. a) Explain the difference between different digital carrier modulation schemes.
b) Draw the block diagram of QPSK system and explain its working. [7+8]
7. a) Define joint and conditional entropies. Give an example.
b) Prove that H(X, Y) = H(X) + H(Y/X) = H(Y) +H(X/Y). [7+8]
8. a) Explain the principle and operation of encoder for Hamming code.
b) The generator matrix for a (6, 3) block code is given below. Find all the code vectors of this code. [7+8]
Set – III
Answer any five questions
All questions carry equal marks
1. a) Compare coherent and non-coherent detection methods of an AM signal.
b) The modulating signal x(t)= 2 cos 2000tp + sin 4000tpis applied to a DSB modulator operating with a carrier frequency of 1MHz. Sketch the power spectral density of the modulator output. [7+8]
2. a) Define the terms sensitivity, selectivity and image frequency as applied to the study of radio receivers.
b) What exactly, does a noise limiter do in AM receiver how does it do this? [7+8]
3. a) Derive an expression for an FM signal with carrier frequency fc and a modulating signal tAtA2211coscos??+. Obtain an expression for the spectrum.
b) An angle modulated signal 83()10cos103sin(2)(10)cxttpp?=+? is present across a 50 ohm resistive load. Find the total average power and peak frequency deviation. [7+8]
4. a) Explain the importance of prediction in DPCM.
b) A signal x(t) = 2 cos 400 tp+ 6 cos 640 tpis ideally sampled at fs = 500Hz. If the sampled signal is passed through an ideal lowpass filter with a cutoff frequency 400Hz, what frequency components will appear in the output? [7+8]
5. a) What is Nyquist criterion of zero ISI? Explain
b) Explain the following
i) Intersymbol interference ii) Eye pattern. [7+8]
6. a) Compare the bandwidth of QPSK system with that of BPSK system.
b) Explain the principle of binary phase shift keying. [7+8]
7. a) State the properties of entropy function.
b) Prove that H(Y/X) = H(Y) with equality if and only if X and Y are independent.[7+8]
8. a) Explain role of minimum distance in error correction and detection.
b) What are the types of errors?
c) For a Hamming distance of 5, how many errors can be detected? How many errors can be corrected? [5+5+5]