Microwave Engg

B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2007 Seventh Semester Electronics and Communication Engineering EC 432 — MICROWAVE ENGINEERING Time : Three hours Maximum : 100 marks Answer ALL questions. PART -A 1. Give the ‘K’ band frequency range. 2. List the mode properties of a propagating waveguide. 3. Give the S —— matrix of H — plane Tee. 4. Define coupling co-efficient and directivity. I 5. What is the purpose of slow wave structures used in TWT? 6. Why Magnetron is called as crossed field device? 7. What is transferred electron effect? 8. State any two applications of parametric amplifier. 9. What is Bolometer? Give two examples. " 10. Name two methods to measure impedance. PART -B 11. (a) Discuss the following properties of ‘S’ matrix. (16) (i) Symmetry property (ii) Unitary property (iii) Phase shift property. OR (b) (i) What is scattering matrix? Derive scattering matrix formulation for ‘n’ port network. (10) (ii) Relate Z,Y and ABCD parameters with ‘S’ parameters. (6) 12. (a) (i)Derive the ‘S’ matrix for Magic Tee. (10) (ii) Explain with diagrams Waveguide corners, bends and twists. (6)

OR (b) (i) What is an isolator? Write down its ‘S’ parameters. (4) (ii) From the first principle derive the scattering matrix parameters of a directional coupler. (12) 13. (a) (i) Draw a neat sketch showing ahelix type traveling wave tube and describe the mechanism of electron bunching. (11) (ii) How does a TWT differ from a Klystron amplifier? (3) (iii) How are the oscillations that are spontaneously generated in a TWT suppressed? (2) OR (b) (i) What is meant by velocity modulation? (2) (ii) Explain the operation of a two cavity klystron amplifier. Derive expressions for bunched beam current and efficiency. (14) 14. (a) Derive the Manley Rowe power relation. Show how it can be applied to find the gain of up converter and down converter. (16) OR (b) Write short notes on (i) GUNN Diode (8 ) (ii) IMPATT device (8 ) 15. (a) With neat block diagram explain how a Network Analyser can be used to measure the amplitude and phase of a signal over a wide frequency range. Also explain the measurement of reflection and transmission parameters and ‘S’ parameters. (16) OR (b) Explain the following : (i) Impedance measurement by reflectometer. (8 ) (ii) Measurement of ‘Q’ by Reflectometer method. (8 )