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SPPU Electronics and Telecom Engineering (Semester 7)
Microwave Engineering
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q1 and Q2
1 (a) The TE10 mode is propagated in a rectangular waveguide of dimensions a = 6cm and b = 4 cm, by means of a travelling detector. The distance between a maximum and minimum is found to be 4.55 cm. Find the frequency of the wave.
7 M
1 (b) State different types of stripline and distinguish between Stripline and Microstrip line in detail.
7 M
1 (c) What is the significance of scattering matrix? Write the properties of S-matrix.
6 M

2 (a) Explain the terms with respect to waveguide:
i) Dominant Mode.
ii) Cut-off Frequency.
iii) Guide Wavelength.
7 M
2 (b) Explain any two applications of circulator.
7 M
2 (c) The collinear ports 1 and 2 of a Magic Tee are terminated by impedances of reflection coefficients ρ1=0.5 and ρ2=0.6. The difference port 4 is terminated by an impedance with reflection coefficient of 0.8. If 1W power is fed at sum port 3, calculate the power reflected at port 3 and the power divisions at the other ports.
6 M

Solve any one question from Q3 and Q4
3 (a) What are the limitations of conventional tubes at microwave frequencies and how to overcome these limitations?
9 M
3 (b) How the oscillations are sustained in Cavity Magnetron? Explain the process of phase focusing effect.
9 M

4 (a) Explain the operation of Travelling Wave Tube with its slow wave Structure.
9 M
4 (b) A two cavity Klystron amplifier has the following specifications:
Beam Voltage : V0 = 900 V
Beam Current : I0 = 30 mA
Frequency : f = 8GHz
Gap spacing in either cavity : d = 1mm
Spacing between centers of cavities : L = 4cm
Effective shunt impedance : Rsh: 40kΩ
Determine:
i) The electron velocity.
ii) The dc transit time of electron.
iii) The input voltage for maximum output voltage.
iv) The voltage gain in decibels.
9 M

Solve any one question from Q5 and Q6
5 (a) Draw equivalent circuit of Varactor diode. Explain in detail its construction and operation.
8 M
5 (b) Explain principle of operation, IV characteristics and equivalent circuit of microwave Tunnel diode.
8 M

6 (a) Explain Gunn effect using two valley model. Mention its typical characteristic and applications of Gunn diode.
8 M
6 (b) With suitable expression explain power frequency limitations of microwave transistor.
4 M
6 (c) In a Gunn diode with active length 20&mulm, the drift velocity of electrons is 2*107 cm/s. Calculate natural frequency of the diode and its critical Voltage.
4 M

Solve any one question from Q7 and Q8
7 (a) Explain any two methods of measuring impedance of a terminating load in a microwave system.
8 M
7 (b) Enlist methods of measuring the Q of a cavity resonator. Explain any one method in detail.
8 M

8 (a) Explain with neat block diagram power measurement of microwave generator using
i) Bolometer.
ii) Calorimeter.
8 M
8 (b) Describe in detail the techniques used for VSWR measurement.
8 M

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