Microwave Devices & Circuits - Dec 2012

Electronics Engineering (Semester 6)

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) List and explain the advantage and disadvantage of microwave along with applications.(5 marks) 1 (b) Differentiate between TWTA and Klystron.(5 marks) 1 (c) Why TM₀₁ or TM₁₀ mode is not possible in rectangular waveguide? (5 marks) 1 (d) Describe the importance of 'S' parameter used in microwave.(5 marks) 2 (a) Obtain an expression for the modulated velocity of the electron beam in Klystron amplifier in terms of beam coupling coefficient β_i and the average gap transit angle θ_g.(12 marks) 2 (b) A Reflex Klystron operates at the peak mode of n = 2 having the beam voltage and beam current of 350V and 15mA respectively. If the signal voltage is 45V. Calculate
(i) Input power
(ii) Output power
(iii) Efficiency(8 marks) 3 (a) Can TEM modes exist in hollow waveguide? Justify your answer.(5 marks) 3 (b) Derive wave equation for TE wave and obtain all the field components in a rectangular waveguide.(10 marks) 3 (c) An air-filled rectangular waveguide of inside dimension 7 x 3.5cm operates in the dominant TE₁₀ mode. Find:
(i) Cut-off frequency.
(ii) Phase velocity of the wave at frequency 3.5GHz.
(iii) Guided wavelength at same frequency.(5 marks) 4 (a) Derive the S-matrix of the E-H plane Tee.(5 marks) 4 (b) Explain microwave propagation in ferrite devices.(5 marks) 4 (c) Explain with neat diagram working of Gyrator.(5 marks) 4 (d) Explain the working of 2-hole directional coupler. (5 marks) 5 (a) Explain in brief construction, principle and working of two valley model of Gunn oscillator.(10 marks) 5 (b) How TRAPATT generates Oscillations?(5 marks) 5 (c) Describe the types of strip lines in details. (5 marks) 6 (a) What are slow wave structures? Explain any one device that uses slow wave structure in detail.(10 marks) 6 (b) Measurement of VSWR.(6 marks) 6 (c) Explain the terms:
Cut-off frequency.
Dominant mode.
Phase velocity.
Wave impedance. (4 marks)

Write short notes on any four:-

7 (a) Magnetron.(5 marks) 7 (b) Cavity resonators.(5 marks) 7 (c) Microwave transistors.(5 marks) 7 (d) Microwave Passive Devices.(5 marks) 7 (e) Measurement of Microwave Power.(5 marks)