Fundamentals of Communication Engg - May 2014
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.
Give brief answers to any four of the following :-
1 (a) Explain ground wave propagation of electromagnetic radiations.(5 marks) 1 (b) Draw the spectrum of an amplitude modulated wave and explain its components.(5 marks) 1 (c) Give advantages and disadvantages of SSB over full carrier DSB amplitude modulated wave.(5 marks) 1 (d) Discuss the factors that influence the modulation index of an FM wave.(5 marks) 1 (e) How is adaptive delta modulation superior to delta modulation?(5 marks) 2 (a) What is a DSBSC wave? Explain its generation using balanced modulator.(10 marks) 2 (b) Discuss the factors that influence the choice of IF in superheterodyne receivers.(5 marks) 2 (c) The maximum deviation allowed in a FM broadcast system is 75 kHz. If the modulation signal is a single tone sinusoidal of frequency 15kHz, find the bandwidth of the FM signal. How does the bandwidth change if the modulating frequency is doubled?(5 marks) 3 (a) How can you use a varactor diode in the generator of FM wave? Explain in detail.(10 marks) 3 (b) List out the advantages and disadvantages of FM over AM.(5 marks) 3 (c) Calculate the thermal noise power available from any resistor at a temperature of 290 K for a bandwidth of 1 Mhz. Calculate also the corresponding noise voltage if the resistance, R=100 Ω(5 marks) 4 (a) Draw the PAM, PWM and PPM waveforms in time domain assuming a sinusoidal modulating signal. Explain them in brief.(10 marks) 4 (b) What do you understand by signal multiplexing? Explain in TDM and FDM with suitable examples.(10 marks) 5 (a) Explain the working of superheterodyne receiver with the help of a neat block diagram. Show the waveforms at the output of each block.(10 marks) 5 (b) Compare analog and digital transmission systems.(5 marks) 5 (c) What is VSB? Mention its application.(5 marks) 6 (a) Pre-emphasis and De-emphasis(5 marks) 6 (b) Automatic gain control(5 marks) 6 (c) Ratio detector(5 marks) 6 (d) Electromagnetic spectrum(5 marks) 6 (e) Noise figure.(5 marks)