Microwave & Radar Engineering - May 2014

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) A waveguide termination having VSWR of 1.1 is used to dissipate 100 watts of power. Find reflected power.(5 marks) 1 (b) Explain different mode of Gunn diodes .(5 marks) 1 (c) Design a circular using Magic Tees(5 marks) 1 (d) justify why rectangular wareguide does not support TEM propagation.(5 marks) 2 (a) With the help of suitable diagram explain mechanism of operation of magnetron? How are various modes separated? Explain the terms frequency pushing and frequency pulling with reference to magnetron(10 marks) 2 (b) Antenna with impedance 50+j30? is to be matched to 100? losslessline with a shorted stub.
Determine: (i) Required stub admittance
(ii) Distance between stub and Antenna
(iii) Stub length
(iv) Standing wave retion between stub and load, stub and source, along the stub (Use smith chart)(10 marks) 3 (a) Describe operation of the following devices using faraday's rortaion principle.
(i) Isolatar
(ii) Cyrator(10 marks) 3 (b) Discuss design procedure for filters using image parameter method.(10 marks) 4 (a) A helix travelling wave tube operates at 4GHz under a beam voltage 10 KV and beam current 500 mA. If the helix impedance is 25 ? and the interaction length is 20 cm. find the output power gain in decibels(10 marks) 4 (b) Explain the working of anegative resistance parametric amplifier and explain its application(10 marks) 5 (a) A slotted line with a short circuit termination measures two successive minimum at 25.3cm apart, when an unknown load is connected, the VSWR is 3.1 and the minimum occures at 16.5 cm position. Find
(i) Voltage reflection coefficient at load
(ii) The load impedance when the characteristics impedance of the line is 50 ?(10 marks) 5 (b) Derive expression for phase velocity, cutoff frequency, cutoff wavelength and field equation for rectangle waveguide.(10 marks) 6 (a) Explain how avalanche devices operate. Name three devices that use the avalanche mode for their operation(10 marks) 6 (b) Explain the working and derive S matrix for a two hole directional coupler.(10 marks) 7 (a) Lorentz Reciprocity theorum(7 marks) 7 (b) Microstrip transmission lines.(7 marks) 7 (c) Periodic Structure(7 marks)