Microwaves & RADAR - Dec 2013

Electronics & Communication (Semester 5)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) What are the applications of smith chart? Explain briefly.(6 marks) 1 (b) Define reflection co-efficient and derive the equation for reflection co-efficient.(10 marks) 1 (c) A transmission line has R=2Ω/m, G=0.5 m℧/m, f=1 GHz, L=8 nH/m, C=0.23 pF. Calculate i) the characteristic impedance ii) the propagation constant.(4 marks) 2 (a) Obtain the expression for wave impedance for TM wave propagation through a rectangular wave guide.(8 marks) 2 (b) An air filled circular waveguide having an inner radius of 1 cm is excited in dominant mode at 10 GHz. Find
(i) the cut off frequency of dominant mode
(ii) guide wave length
(iii) wave impedance(4 marks) 2 (c) Explain the construction, working and application of isolator based on Faraday rotation.(8 marks) 3 (a) Explain construction and operation of Gunn diode in the Gunn mode and LSA mode.(10 marks) 3 (b) With neat diagram, explain the construction operation of IMPATT diode and mechanism of oscillations.(10 marks) 4 (a) State and explain the properties of S-parameters.(8 marks) 4 (b) Explain S-matrix representation of multiport network.(8 marks) 4 (c) Write the relationship of ABCD parameters with Z-parameters.(4 marks) 5 (a) With a neat diagram, explain the operation of microwave attenuator.(6 marks) 5 (b) Explain the characteristics of a magic tee, obtain S-matrix representation.(10 marks) 5 (c) Explain the construction of a co-axial cable.(4 marks) 6 (a) Explain the construction and field patterns for microstrip line.(8 marks) 6 (b) Explain the different losses taking place in microstip line.(6 marks) 6 (c) A shield strip line has dielectric constant of the insulator ?_r=2.5k6, strip width W=25 mils, strip thickness t=14 mils, shield depth d=70 mils. Calculate (i) K factor (ii) the fringe capacitance (iii) the characteristic impedance of the line.(6 marks) 7 (a) Derive the simple radar range equation.(10 marks) 7 (b) A marine radar operating at 10 GHz has a maximum range of 50 kW and a minimum detectable single of 10^-11 W. Determine the cross-section of the target the radar can sight.(4 marks) 7 (c) Explain briefly the application of radars.(6 marks) 8 (a) With a neat block diagram, explain working principles of MTI radar.(10 marks) 8 (b) With a neat block diagram, explain operating of a pulse Doppler radar.(10 marks)