Microwaves & RADAR - Dec 2014

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) Define reflection coefficient. Derive the equation for reflection coefficient at the load end and at a distance 'd' form load end.(10 marks) 1(b) A transmission line has the following primary constants per km of the line R: 8Ω, G=0.1μ℧, L=3.5mH, C=9nF. Calculate zo, α, β,u_p and γ at w=5000rad/sec.(5 marks) 1(c) A transmission line and characteristic impedance of 50+j0.01Ω and is terminated in a load impedance of 72-j42.5Ω. Calculate i) the reflection coefficient; ii) Standing wave ratio(5 marks) 2(a) Derive electric and magnetic field equation in rectangular wave guides for TE modes.(12 marks) 2(b) Write a brief note on dominant mode degenerate mode.(4 marks) 2(c) An air - filled rectangular waveguide of inside dimension 7 × 3.5 cm operates in the dominant TE₁₀ mode. Find cutoff frequency,phase velocity,guided wavelength of the wave in the guide at a frequency of 3.5 Ghz.(4 marks) 3(a) Mention the four modes of operation for gunn diode. Explain briefly the gunn oscillation mode.(10 marks) 3(b) Draw the equivalent circuit for parametric amplifier and explain in brief the parametric up converter.(5 marks) 3(c) Explain the principle of operation of read diode with suitable diagram.(5 marks) 4(a) State the properties of S- parameter. Prove the symmetry property and unitary property of S- parameter.(10 marks) 4(b) Explain S-matrix representation of multiport network.(6 marks) 4(c) Define the following losses in microwave network in terms of s parameter :
i) Insertion loss ii) Transmission loss.(4 marks) 5(a) Explain with a neat sketch a precision type variable attenuator.(6 marks) 5(b) Explain magic tee and derive the S- matrix and mention its application.(10 marks) 5(c) Write a brief note on phase shifter.(4 marks) 6(a) Explain the construction and filed pattern for micro strip line.(8 marks) 6(b) what are the losses in microstrip lines? Explain radiation losses.(8 marks) 6(c) Compare strip line microstrip line.(4 marks) 7(a) Derive an expression for simple form of the radar range equation(8 marks) 7(b) A ground radar operates at 3cm. The radar transmitter using an antenna of gain 50dB. Produces 100 kW. The receiver minimum detectable signal is$$S_{min}=10^{-13}$$ W. The maximum radar range is given as 259km. Find the cross section of the target the radar can detect.(8 marks) 7(c) Write a brief note on maximum unambiguous range.(4 marks) 8(a) With a neat diagram,explain the advantage of I and Q channels in digital MTI Doppler signal processor.(6 marks) 8(b) Explain the principle and working of MTI radar with the help of block diagram.(10 marks) 8(c) Explain single delay line canceller with neat block diagram. Derive an expression for frequency response of single DLC.(4 marks)