## Microwaves & RADAR - Dec 2016

### 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 equations for voltage and currents for transmission line.(8 marks)
**1(b)** The characteristics impendance of a certain line is &neg; 10∠-16°, when frequency is Khz. At this frequency the attenuation is 0.071 NP/km phase constant is 0.35 rads/km. Calculate resistance, inductance capacitance for 1 km and also velocity of propagation.(6 marks)
**1(c)** Determine the input impedance of a 200Ω line, 3/8 wavelengths long terminated i 100Ω resistance, using smith chart. Also find k in magnitude and angle.(6 marks)
**2(a)** What are the properties of wave guide? Obtain the expression for Hz in the case of T.E. waves applying all boundary conditions.(8 marks)
**2(b)** The cut-off wave lengths of a rectangular waveguide was measured to be 8 cm and 4.8 cm when excited in TE_{10} and TE_{11} modes respectively. Determine the dimensions of the wave guide.(6 marks)
**2(c)** Explain the working of a four port circulator.(6 marks)
**3(a)** With a neat sketch expalin how PIN diode acts as a swtich. Find the expression for insertion loss.(8 marks)
**3(b)** Explain RWH theory in GUNN diodes and give its constructional details.(6 marks)
**3(c)** Calculate the operating frequency of silicon based IMPATT diode with drift length of 2μm and drift velocity of 10^{7} cm/sec.(6 marks)
**4(a)** Give the S-matrix representation for multiport network. Also explain the properties of S-matrix.(8 marks)
**4(b)** What is an H-plane Tee junction? Derive its S-matrix.(6 marks)
**4(c)** What are phase shifters? Explain a rotary precision phase shifter with a neat sketch.(6 marks)
**5(a)** Explain a magic Tee structure and its S-matrix. Also give its various applications.(8 marks)
**5(b)** What are micro strip lines ? Explain the field distribution with a neat sketch.(6 marks)
**5(c)** A micro strip line is composed of zero thickness 2.4 mm. If the line width is 1 mm and operated at 10 Ghz. Calculate Zo, the attenuation due to conductors and dielectric loss.(6 marks)
**6(a)** Name the various types RADAR. Derive the radar range equation.(8 marks)
**6(b)** A 1 kW, 3GHz radar uses single antenna with a gain of 30 dB. The receiver has noise band width of 1KHz and noise factor of 5 dB. A target of echoing area of 10 m ^{2} at a range of 10 nautical miles is to be detected. Calculate the minimum S/N.(6 marks)
**6(c)** Explain block diagram of a radar with a neat diagram and explain each block.(6 marks)
**7(a)** Explain with a neat diagram the working of a coherent MTI radar.(8 marks)
**7(b)** Explain the various applications of radar.(6 marks)
**7(c)** Explain the need of delay line cancellers in MTI radars. Also give the characteristics of single delay line canceller.(6 marks)
**8(a)** Explain with a neat block diagram the working of a simple digital MTI signal processor.(7 marks)
**8(b)** Explain the working of a moving target detector with block diagram.(7 marks)
**8(c)** Explain with a neat block diagram the working of a pulse Doppler RADAR.(6 marks)