Principles of Analog & Digital Comm. - May 2013
Information Technology (Semester 3)
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.
Attempt any four of the following
1 (a) What are the advantages of SSB transmission over DSB-FC? Why is SSB transmission not generally used for broadcasting applications(5 marks)
1 (b) Define the following terms:
(i) Noise Figure
(ii) Noise Temperature(5 marks) 1 (c) A single tone FM signal is given by VFM=10sin(16?x166t + 20sin2?x103t) volt. Find:
(i) Maximum frequency deviation
(ii) Bandwidth of FM using Carson's Rule.(5 marks) 1 (d) What is aliasing error? How can we prevent it?(5 marks) 1 (e) What is double spotting in a radio receiver?(5 marks) 2 (a) Find the Fourier Transform of the following:
(ii) sin?0t(10 marks) 2 (b) What are the different methods of FM generation? Sketch the circuit and explain the principle of reactance modulator. Why is direct modulation not preferred for FM generation?(10 marks) 3 (a) A sinusoidal carrier has an amplitude of 20V and a frequency of 200KHz. It is amplitude modulation by a sinusoidal voltage of amplitude 6V and frequency 1KHz. Modulated voltage is developed across a 80? resistance.
(i) Write the equation for the modulated wave
(ii) Determine the modulation index
(iii)Draw the spectrum of modulated wave
(iv)Calculate the total average power
(v)Calculate the power carried by side bands(12 marks) 3 (b) (i) Compare : TDM and FDM(4 marks) 3 (b) (ii) Compare : PCM and DM(4 marks) 4 (a) With a block schematic, explain the operation of ISB transmitter with pilot carrier. What is the advantage of transmitting a pilot carrier(10 marks) 4 (b) What is companding? State its advantages.(4 marks) 4 (c) Explain slope overload and hunting error in Delta modulation.(6 marks) 5 (a) What are the limitations of Tuned RF receiver? Draw the block diagram of superheterodyne AM receiver and describe the function of each block.(10 marks) 5 (b) With the help of neat block diagram explain the generation and detection of a PPM signal. Also state the merits and demerits of a PPM transmission.(10 marks) 6 (a) Explain different types of communication channels and their characteristics.(10 marks) 6 (b) Compare AM and FM(5 marks) 6 (c) Explain Pre-emphasis and De-emphasis in FM(5 marks)
Write short notes on:
7 (a) Automatic Frequency Control (AFC)(5 marks) 7 (b) Application of multiplexing technique in wireless communication(5 marks) 7 (c) Frequency shift keying(5 marks) 7 (d) AGC principle in AM receivers.(5 marks)