Microwave & Radar Engineering - Dec 2011

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) Give reasons Why GaAs MESFET perform better than Si MESFET(5 marks) 1 (b) Explain microwave propagation in Ferrites(5 marks) 1 (c) State and explain Lorentz Reciprocity Theorem(5 marks) 1 (d) An IMPATT diode has a drift length of 2 ?m and drift velocity is of the order of 10⁵ m/s. Determine-
(i) the drift time of the carriers
(ii) the operating frequency of the IMPATT diode.(5 marks) 2 (a) Mention different types of electron flow. Explain Brillouin flow and derive an expression for Brillouin magnetic field Br.(10 marks) 2 (b) Describe the mechanism of velocity modulation in a two cavity klystron and hence obtain an expression for the bunched beam current. Also find out condition for maximum power output.(10 marks) 3 (a) A microstrip transmission line uses a subtrate with dielectric constant ?_r=9.7 and thickness 0.5 mm. the stripwidth is also 0.5 mm. find the effective dielectric constant, the characteristics impedance and the microstrip wavelength at a frequency of 2 GHz.(8 marks) 3 (b) Discuss the differences between transferred electron devices and avalanche transit time devices. Give example(6 marks) 3 (c) Discuss the factors that limit the high frequency response of a microwave BJT.(6 marks) 4 (a) Design a double stub matching system to match a normalized load admittance y_L=0.4+j1. the stubs ae spaced ?/8 apart(10 marks) 4 (b) Discuss the operation of backward wave devices(10 marks) 5 (a) What are different microwave band classification? Give applications of various microwave bands. What is the band rectangle waveguide with dimensions 2.3 cm and 1 cm(10 marks) 5 (b) Calculate -(i) generated power (ii) the total r.f. power output (iii) the power gain in dB for a CFA operating with the following parameters:-
Ancode dc current l_a0 = 1.30 Amp
Anode dc voltage -V_a0 = 1.80 KV
Electronic effciency= ?_e = 22%
Input r.f. power P_in =70 Watts(10 marks) 6 (a) Explain the working of Magic Tee. Design a circulator using Magic Tees.(10 marks) 6 (b) Design a low pass composite filter with cutoff frequency of 2 MHz and impedance of 75 ?. Place the infinite attenuation pole at 2.05 MHz(10 marks) 7 (a) Explain the working of a negative resistance parameteric amplifier(10 marks) 7 (b) Explain the procedure of measurement of Dielectric constant at microwave frequency.(10 marks)