Analog Communications B.Tech Question Paper : vardhaman.org
College : Vardhaman College Of Engineering
Degree : B.Tech
Department : Electronics & Communication Engineering
Semester : V
Subject : Analog Communications
Document type : Question Paper
Website : vardhaman.org
Download Previous / Old Question Papers :
June – 2014 :https://www.pdfquestion.in/uploads/vardhaman.org/6376-BT5S%20JUNE14.pdf
December – 2013 : https://www.pdfquestion.in/uploads/vardhaman.org/6376-B.%20Tech%20V%20Semester%20Regular%20Examinations%20December%20-%202013.pdf
Analog Communications Question Paper :
Four Year B. Tech V Semester Supplementary Examinations June – 2014
(Regulations: VCE-R11)
(Electronics and Communication Engineering)
Date: 19 June, 2014 FN
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Related / Similar Question Paper :
Vardhaman College B.Tech Digital Design Through Verilog Hdl Question Paper
All parts of the question must be answered in one place only :
Unit – I :
1. a) Explain with circuit diagram, the generation of AM wave using switching modulator with analysis and spectrum? 8M
b) Consider the message signal m(t)=20 Cos 2pt Volts and the carrier wave c(t)=50 Cos(100pt) volts. Give the time time-domain expression for the resulting conventional AM wave for 75% modulation. Find the power developed across a load of 100O due to this AM wave. 7M
2. a) Explain in brief, the block diagram representation of Coastas receiver suitable for demodulating DSBSC waves? 8M
b) The output current of 60 percent modulated AM generator is 1.5A. To what value will this current rise if the generator is modulated additionally by another audio sine wave, whose modulation index is 0.7? What will be the percentage power saving if the carrier and one of the sidebands are now suppressed. 7M
Unit – II :
3. a) Explain coherent detection of SSBSC wave? 8M
b) Find the Hilbert transform of the pulse given in below Fig.1. Fig.1 7M
4. a) Explain generation of VSBSC using filtering technique? 8M
b) Explain envelope detection of VSBSC wave? 7M
Unit – III :
5. a) Derive an expression for wideband FM wave with sinusoidal modulation. 8M
b) In an FM system, when the audio frequency is 500Hz and modulating voltage is 2.5V, the deviation produced is 5K Hz. Calculate the new value of frequency deviation produced if the AF voltage is raised to 10 V while the modulating frequency dropped to 250Hz. Calculate the modulation index in each case. 7M
6. a) Explain the two methods of generating FM waves? 10M
b) Explain the FM demodulation using slope detection method? 5M
Unit – IV :
7. a) Explain De-emphasis and pre-emphasis in FM? 7M
b) Prove the figure of merit of FM is (3/2) ß2. 8M
8. a) Find the figure of merit of DSBSC (Double Sideband Suppressed Carrier)? 8 M
b) Explain how noise effects the performance of analog modulation systems? 7M
Unit – V :
9. a) With neat block diagram explain the working of super heterodyne receiver 8M
b) An AM receiver has an IF 455 kHz and is tuned to 1000kHz, the tuned circuit in RF stage has a Q of 60. Find:
i. Image frequency
ii. Image rejection in db’s 7M
10. a) Find the image frequency range for a receiver which tunes 40 to 10 MHz with an IF of 1.8MHz do any of the image frequencies fall in the receiver pass band if IF circuits have a combined Q of 50 at the top end of the band. Find the image rejection ratio in decibels at that frequency. 8M
b) Explain FM stereo broadcast transmitter? 7M
B. Tech V Semester Regular Examinations, December – 2013 :
(Regulations: VCE-R11)
Analog Communications :
(Electronics and Communication Engineering)
Date : 12 December, 2013
Time : 3 Hours
Max. Marks : 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
All parts of the question must be answered in one place only :
Unit – 1 :
1. a) Explain the demodulation of an AM wave using an envelope detector. 8M
b) When a broadcast AM Transmitter is 50 percent modulated its antenna current is 12A. What will be the current when the modulation depth is increased to 0.9? 7M
2. a) With a neat block diagram explain the synchronous receiving system for receiving DSBSC modulated wave. 8M
b) A 360W carrier is simultaneously modulated by two sin waves with waves with modulation percentage of 55 and 65 respectively what is the total sideband power radiated. 7M
Unit – 2 :
3. a) Explain SSB wave generation using phase shift method with relevant diagrams and equations. 8M
b) In a coherent detection of SSBSC, if the carrier applied is Cos (2pfct+f) prove that there is a phase error in the output i.e output consists not only the message signal but also its Hilbert transform. 7M
4. a) Explain vestigial side band modulation. Represent the VSB modulated wave in time domain. 8M
b) Calculate the percentage power saving when the carrier and one of the side bands are suppressed in an AM wave modulated to a depth of
i) 100% ii) 50% 7M
Unit – 3 :
5. a) Derive the equation for FM wave, derive Modulation Index and Frequency Deviation for single tone. 8M
b) Describe with necessary diagram generation of Narrow Band Frequency Modulation and also compare Narrow Band FM and Single tone AM. 7M
6. a) an angle modulated signal is defined by s(t)=10Cos[2p. 106t +0.2sin 2000pt] volts find the following:
i. The power in the modulated signal
ii. The frequency deviation ?f
iii. Phase deviation ?
iv. Approximate transmission bandwidth 8M
b) Explain with a block diagram the phase locked loop for the demodulation of FM signal.7M