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Posted By: Sra1 Member Level: Diamond Posted Date: 28 May 2008
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2007 Jawaharlal Nehru Technological University B.Tech Electronics COMMUNICATION ENGINEERING (Supplimentary Examinations, November 2007) Question paper
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Set No 2
---------------------
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
1. (a) An AM transmitter has antenna current of 2A with modulation index of 60 percent. What will be the total antenna current if one more identical antenna is connected in parallel with the previous one, keeping the transmitter output same? Will it affect the modulation index?
(b) An audio frequency signal 10 sin(2p × 500t) is used to amplitude modulate a carrier of 50 sin 2p105t. Calculate
i. Modulation index
ii. Side band frequencies
iii. Amplitude of each side band frequencies
iv. Bandwidth required
v. Total power delivered to the load of 600 ohms
vi. Transmission efficiency. [8+8]
2. (a) Explain Balanced slope detector for detecting FM signal.
(b) The maximum deviation allowed in an FM broadcast system is 75 KHz. If the modulating signal is a single-tone sinusoid of 10 KHz, find the bandwidth of the FM signal. [12+4]
3. (a) Explain the operation of ISB transmitter with block diagram. Where it is used?
(b) What is the function of crystal filters in SSB transmitter?
(c) State and explain with respect to ‘Q’, various types of filters used to separate side bands? [4+6+6]
4. (a) What are the drawbacks of Tuned Radio frequency receivers and explain how they are overcome in superheterodyne receivers?
(b) Discuss the criteria for the choice of local oscillator frequency and Intermediate Frequency (IF) in a superheterodyne receiver. [8+8]
5. (a) Derive Noise figure formula for cascaded network
(b) A mixer circuits has a noise figure of 12 dB. It is preceded by an amplifier that has an equivalent noise temperature of 200 K and a power gain of 30 dB. Calculate the equivalent noise temperature of the combination referred to the amplifier input. [8+8]
6. (a) Discuss the principle behind the Frequency Division Multiplexing.
(b) Compare and contrast PAM, PWM, PPM methods. [6+10]
7. (a) Draw the block diagram of a Delta Modulation and explain its operation with waveform.
(b) What is meant by Slope-overload error in Delta modulation? Explain. [8+8]
8. (a) Write the comparisons of communication switching techniques?
(b) Draw the event timing for circuit switching and packet switching and explain? [8+8]
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