Microwave & Radar Engineering - Dec 2015

Electronics & Telecomm. (Semester 7)

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. 1 (a) Design circulator using magic tees.(5 marks) 1 (b) Explain travelling wave tube as an amplifier.(5 marks) 1 (c) Explain the operation of 2-holes Directional coupler with s-matrix.(5 marks) 1 (d) Explain Doppler shift and its role in pulsed and CW radar.(5 marks) 2 (a) The terminating impedance Z_L is 100+j100Ω and the characteristics impedance Z₀ of the line and stub is 50Ω. The first stub is placed at 0.40λ away from the load. The spacing between the two stubs is 3λ/8. Determine the length of the short circuited stubs when the match is achieved.(10 marks) 2 (b) Explain instrument landing system for aircraft navigation.(10 marks) 3 (a) Derive the wave equation for a TE wave and obtain all the field components in a circular waveguide.(10 marks) 3 (b) What is the importance of beam coupling coefficient? Derive the equation of velocity modulation in klystrom.(10 marks) 4 (a) Explain the significance of RWH model and two valley model in Gunn diode.(10 marks) 4 (b) With a suitable diagram, explain the working on conical scan tracking radar. Explain the various factors that need to be considered in determining the optimum squint angle.(10 marks) 5 (a) Draw and explain with block diagram of MTI radar system. What are its limitations.(10 marks) 5 (b) Discuss the power frequency. Current frequency and power gain frequency limitations with reference to a microwave transistor.(10 marks) 6 (a) Design two lumped element L section matching network at 500 MHz to transform Z_L=200 - j100Ω to a 100Ω transmission line. Use Smith Chart.(10 marks) 6 (b) Write a short note one backword wave oscilator.(5 marks) 6 (c) A radar operating at 1.5 GHz uses a peak pulse power of 2.5 MW and have a range of 100 nmi for objects whose radar cross section is 1m². If the minimum receivable power of the receiver is 2×10^-13 Watt. What is the smallest diameter of the antenna reflector could have, assuming it to be a full paraboloid with η=0.65.(5 marks)