IGNOU PHE-16 - Communication Physics

1. State with reasons whether the following statements are True or False. i) Wireless communication need not be serial. ii) Modulator is an inherent part of any communication system. iii) It is advantageous to have a transmission line with reflection coefficient = 1. iv) Modulation can be used to reduce noise present in the input signal. v) Numbering plan is unique world-wide. vi) Mixer can be designed using passive components, viz. L, C and R. vii) Bayer Mask has larger blue component. viii) Splicing involves soldering. ix) Star topology is most rugged. x) Blue tooth works only for mobile devices. 2. a) Explain the physical significance of all four parameters/characteristics of any receiver. b) Explain the role of temperature in the noise observed in communication systems. c) Why are hollow waveguides preferred over metallic conductors at microwave frequencies? 3. a) A plane wave is described by an electric field What is its (i) frequency in Hz, (ii) wave number, (iii) phase velocity, and (iv) wavelength? b) What is the physical significance of standing wave ratio? c) What is the characteristic impedance of a transmission line with distributed inductance of 400 mH m-1 and distributed capacitance of 4. a) Why is frequency stabilization required in FM generator? b) What is the advantage of dual slope detector over single slope detector? c) Draw the bipolar RZ and Manchester code waveforms of 1011001101. Show appropriate clock waveform also. 5. a) Trace the journey of the signal from the moment you dial a number till the called party picks up the call in a mobile telephone system. b) Design and draw the circuit diagram of a TDM system to handle 3 PAM channels of video signals. Specify the sampling frequency per channel and idle time between samples. 6. a) What are the advantages of superheterodyne receiver over TRF receiver? b) Explain the working of CCD camera. c) What are the advantages of LCD/Plasma TV over vacuum tube TV? 7. a) Two microwave receivers are situated at 2 km and 20 km distance from a transmitter. If the total attenuation of the signal is 40 dB, what is the power attenuation of the absorbing medium? b) In an optical fibre, the refractive index of core is 1.5 and that of cladding is 1.48. Calculate its critical angle. What is its numerical aperture and acceptance angle if immersed in water? (Assume the refractive index of water to be 1.33) 8. a) Why is network security necessary? Explain, how it can be implemented. b) Explain the techniques generally used to provide firewall protection. 9. a) Explain the configuration in place for accessing global Internet from a PC. b) Compare the OSI and TCP/IP reference models.