# Pune University BE Question Papers Microwave Communication and Radar

B.E. (E & TC) MICROWAVE COMMUNICATION & RADAR (2008 Pattern) (Sem. – I) (Elective – I)

Time :3 Hours]                                                                                              [Max. Marks :100

Instructions to the candidates:-

1)            Answer three questions from section I and three questions from section II.

2)            Answers to the two sections should be written in separate answer books.

3)            Neat diagrams must be drawn wherever necessary.

4)             Figures to the right indicate full marks.

5)            Assume suitable data, if necessary.

SECTION – I

QI) a) Explain the following waveguide parameters.                                                   

i)  off wavelength        ii) Guide wavelength

iii)    Phase velocity    iv) Wave impedance

v) Dominant mode

b)        Explain the different power losses takes place in a rectangular waveguide. 

c)         State the assumptions while calculating power in waveguide.                   

OR

Q2) a) What is re-entrant cavity? Explain where it is used?                                          

b)        Draw different field patterns for TE mode.                                                    

c)        Explain the need of coupling probes 8 loops along with diagrams. 

Q3) a) Determine the scattering parameters for 10dB directional coupler. The directivity D = 30dB. Assume that it is lossless and VSWR at each port is 1.0 under matched conditions. Designate the ports in the main guide as 1 or 2 and ports in the auxillary guide as 3 and 4.                                                                                                                           

b) Explain in brief the following                                                                             

i)             Waveguide transitions

ii)           Matched termination.

OR

Q4) a) State and explain the properties of S parameters.                                                

b) Explain the construction, working and application of isolator based on Faraday’s rotation.                                                                                                                        

Q5) a) i) A reflex klystron operates under the following conditions.  V = 600 v L = I mm f = 9 GHz 0r

e/m = 11.759 x 1011 The tube is operating at fr at the peak of n = 2 mode. Find the value of repeller voltage.

ii)            What is a slow wave structure? What are their types? Which one is most practical?                                                                                                                     

b) Compare two cavity klystron and reflex klystron with relevant sketches. 

OR

Q6) a) What are cross field devices? Explain the n mode of oscillation in magnetron.      

b) i) Explain how mode jumping is avoided in magnetron.                               

i)               What are the limitations of conventional tubes at microwave frequencies.         

SECTION – II

Q7) a) Explain principle of operation, I-V characteristic and equivalent circuit of microwave Tunnel  iode.                                                                             

b) Discuss the amplification mechanism of parametric amplifier with the help of its equivalent  ircuit.                                                                                       

OR

Q8) a) Explain the various modes of operation of Gunn diode.                                    

b) Explain in brief any one of the transit time devices.                                                                                

Q9) a) Explain how VSWR, impedance and frequency can be measured using a slotted waveguide.                                                                                                                               

b) Explain in brief network analyser.                                                                                                       

OR

Write a short note on measurement of noise factor.                                     

Describe the setup for the measurement of Q of a cavity resonator.         

Sketch a general setup of microwave bench.                                                

A marine radar operating at 10 GHz has a maximum range of 50 km with an antenna gain of 4000. If the transmitter has a power of 250kw and minimum 250 kw also minimum detectable signal of 10r11 W. Determine the cross section of the target the radar can sight.      

Explain A scope and PPI displays with reference to radars. What are their limitations.    

Explain the action of