Fundamentals of Communication Engg - May 2015

Electronics Engineering (Semester 4)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer the following (any four):

1 (a) Classify and explain the various noise that effect communication.(5 marks) 1 (b) DSB-FC (AM) is a wastage of power and bandwidth. Justify.(5 marks) 1 (c) Derive the expression for frequency modulated wave.(5 marks) 1 (d) What are pre-emphasis and de-emphasis.(5 marks) 1 (e) Explain companding and its need is communication.(5 marks) 2 (a) Explain basic block diagram of communication system in detail.(6 marks) 2 (b) Explain the following terms
i) Signal to noise ratio
ii) Noise factor
iii) Noise figure
iv) Equivalent noise temperature(8 marks) 2 (c) Write short note on vestigial side-band transmission.(6 marks) 3 (a) Explain with the help of circuit diagram and waveform any one method of FM-generation.(10 marks) 3 (b) Comment on bandwidth of FM wave.(4 marks) 3 (c) An AM broadcast transmitter has a carrier power output of 100 kw. Find the total power and side-band power with 75% modulation.(6 marks) 4 (a) The maximum deviation allowed in an FM broadcast system is 75KHz. If the modulating signal is a single tone sinusoidal signal of 20 KHz, find the bandwidth of FM signal using Carson's rule. What will be the change in band width if modulating signal frequency is doubled? Determine the bandwidth when modulating signal amplitude is doubled.(10 marks) 4 (b) Draw the block diagram of Adaptive delta modulation system and explain its operation. What are the advantages of this over delta modulation.(10 marks) 5 (a) Explain frequency demodulation system using phase discriminator. Draw the circuit diagram and phasor diagram.(10 marks) 5 (b) Explain in detail generation and detection of PPM.(10 marks)

Write short notes on any four of the following:

6 (a) Electromagnetic frequency spectrum.(5 marks) 6 (b) Frequency division multiplexing.(5 marks) 6 (c) Sampling theorem.(5 marks) 6 (d) Automatic Gain Control(5 marks) 6 (e) Image Frequency Rejection.(5 marks)