Microwave & Radar Engineering - Dec 2013

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) Explain the relationship between work and energy at microwave frequency.(5 marks) 1 (b) Justify why waveguide does not support TEM propagation.(5 marks) 1 (c) How can circulator be implemented using 2 Magic TEE's and phase shifter of 180^o(5 marks) 1 (d) Differentiate between Transit time devices and Transferred Electron devices.(5 marks) 2 (a) How matched impedance is achieved in transmission line? Explain any one method in detail.(10 marks) 2 (b) Explain the construction and working of Microwave FET in detail.(10 marks) 3 (a) Why phase focussing is required in magnetron? What is back heating? How it can be controlled? (10 marks) 3 (b) Explain the significance of RWH model and two valley model in GUNN diode .(10 marks) 4 (a) Explain wave propagation in circular waveguide in detail.(10 marks) 4 (b) What are 'O' type tubes? Explain. A TWT operates under following parameters:
Beam voltage : 2.5 KV
Beam current : 50 mA
Characteristic impedance of helix : 6.75Ω
Circuit Length : 45
Frequency : 8 GHz
Determine gain parameter, power gain and all four propagation constants.
(10 marks) 5 (a) A waveguide has internal length of 3cm and carries the dominant mode of a signal of unknown frequency. If Z_TE is 500Ω, what is this frequency?(10 marks) 5 (b) What are periodic structures? Why are they termed as filters.(10 marks) 6 (a) Why are detectors used at microwave frequency ? Explain its application in detail.(10 marks) 6(b) Design a Butterworth low pass filter with microwave components of order 4 with R₀=50 Ω operating at a frequency of 3 GHz . (10 marks) 7 (b) Resonating Re-entrant cavities .(5 marks) 7 (c) Microstrip transmission lines.(5 marks) 7 (d) Diode used in Parametric Devices.(5 marks)

Write short notes on:

7(a) Measurement of VSWR.(5 marks)