Question Paper: Microwaves & RADAR : Question Paper Jun 2015 - Electronics & Telecomm (Semester 5) | Visveswaraya Technological University (VTU)
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## Microwaves & RADAR - Jun 2015

### Electronics & Communication (Semester 5)

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) Derive:
1) Voltage and current equations on a transmission line.
2) The Characteristic impedance of the line.
3) Propagation constant.
4) Phase velocity.
5) The relative phase velocity factor.
(12 marks)
1 (b) What is impedance matching? Explain single stub matching and double stub matching.(8 marks) 2 (a) Derive TEmn field equation in rectangular waveguide and define cut off wave number, cut-off frequency, propagation constant, phase velocity, character wave impedance and wave length in the guide.(10 marks) 2 (b) Explain why TEM mode is not possible in waveguides.(2 marks) 2 (c) Explain faraday rotation and discuss microwave circulator.(8 marks) 3 (a) Discuss the criterion for classifying the modes of operation for Gunn effect diodes. For a transit time domain made; the domain velocity is equal to the current drift velocity is 107 cm/s. Determine the drift length of the diode of a frequency of 8GHz(7 marks) 3 (b) Explain how carrier current I0(t) and external current Ie(t) are generated when a read diode is mounted in a microwave resonant circuit, with the aid of diagrams for structure of read diode, field distribution, applied ac voltage and I0 (t) and Ie(t).(7 marks) 3 (c) Write equivalent circuit for a parametric amplifier. AN up-converter parametric amplifier has the following parameters:
i) Figure of merit; γQ=8
ii) Ratio of output frequency over signal frequency f0/fδ
iii) Factor of merit figure;γ=0.2
iv) Diode temperature Td=300°t.
Calculate : i) The power gain in dB; ii) The noise figure in dB; iii) Bandwidth.
(6 marks)
4 (a) What is a reciprocal network? For a reciprocal microwave N-port network prove that the admittance and impedance matrices are symmetrical.(7 marks) 4 (b) State and prove the following properties of S-parameters
i) Symmetry property for a reciprocal network.
ii) Unitary property for a lossless junction.
(8 marks)
4 (c) The impedance matric of a passive network is given by $$Z=\begin{bmatrix} 4 &3 \\1 &2 \end{bmatrix}$$, find scattering matrix.(5 marks) 5 (a) Why are co-axial connectors and adaptors used? List six types of co-axial connectors with their frequency ranges.(5 marks) 5 (b) What are waveguide tees? Explain with the aid of neat diagram, E-plane tree and H-plane tree.(9 marks) 5 (c) List four applications of Magic T. Explain Magic-Tee as a microwave mixer.(6 marks) 6 (a) Show that for a micro trip line, the quantity factors is Qc$$Q_{c}=0.636\sqrt[h]{\sigma f_{CH_{2}}}$$.(7 marks) 6 (b) A gold parallel strip line has the following parameters
Relative dielectric constant of polyethylene εrd2.25.
Strip width; W=25mm
Separation width; d=5mm
Calculate:
i) Characteristic impedance of the strip line
ii) Strip-line capacitance
iii) Strip-line inductance
iv) Phase velocity.
(8 marks)
6 (c) Write a note on coplanar stripline.(5 marks) 7 (a) What is radar? With a neat block diagram explain the operation of radar.(8 marks) 7 (b) Explain the various forms of radar equation.(6 marks) 7 (c) Discuss the application the radar.(6 marks) 8 (a) With a neat block diagram, explain CW Doppler radar.(8 marks) 8 (b) Explain a simple MTI delay line canceller.(8 marks) 8 (c) Discuss the difference between MTI and Doppler radar.(4 marks)