## Microwaves & RADAR - Dec 2013

### 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)** What are the applications of smith chart? Explain briefly.(6 marks)
**1 (b)** Define reflection co-efficient and derive the equation for reflection co-efficient.(10 marks)
**1 (c)** A transmission line has R=2Ω/m, G=0.5 m℧/m, f=1 GHz, L=8 nH/m, C=0.23 pF. Calculate i) the characteristic impedance ii) the propagation constant.(4 marks)
**2 (a)** Obtain the expression for wave impedance for TM wave propagation through a rectangular wave guide.(8 marks)
**2 (b)** An air filled circular waveguide having an inner radius of 1 cm is excited in dominant mode at 10 GHz. Find

(i) the cut off frequency of dominant mode

(ii) guide wave length

(iii) wave impedance(4 marks)
**2 (c)** Explain the construction, working and application of isolator based on Faraday rotation.(8 marks)
**3 (a)** Explain construction and operation of Gunn diode in the Gunn mode and LSA mode.(10 marks)
**3 (b)** With neat diagram, explain the construction operation of IMPATT diode and mechanism of oscillations.(10 marks)
**4 (a)** State and explain the properties of S-parameters.(8 marks)
**4 (b)** Explain S-matrix representation of multiport network.(8 marks)
**4 (c)** Write the relationship of ABCD parameters with Z-parameters.(4 marks)
**5 (a)** With a neat diagram, explain the operation of microwave attenuator.(6 marks)
**5 (b)** Explain the characteristics of a magic tee, obtain S-matrix representation.(10 marks)
**5 (c)** Explain the construction of a co-axial cable.(4 marks)
**6 (a)** Explain the construction and field patterns for microstrip line.(8 marks)
**6 (b)** Explain the different losses taking place in microstip line.(6 marks)
**6 (c)** A shield strip line has dielectric constant of the insulator ?_{r}=2.5k6, strip width W=25 mils, strip thickness t=14 mils, shield depth d=70 mils. Calculate (i) K factor (ii) the fringe capacitance (iii) the characteristic impedance of the line.(6 marks)
**7 (a)** Derive the simple radar range equation.(10 marks)
**7 (b)** A marine radar operating at 10 GHz has a maximum range of 50 kW and a minimum detectable single of 10^{-11} W. Determine the cross-section of the target the radar can sight.(4 marks)
**7 (c)** Explain briefly the application of radars.(6 marks)
**8 (a)** With a neat block diagram, explain working principles of MTI radar.(10 marks)
**8 (b)** With a neat block diagram, explain operating of a pulse Doppler radar.(10 marks)