RF Modelling and Antennas - May 2014

Electronics & Telecomm. (Semester 5)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

1(a) Explain the terms Insertion Loss, Ripple factor and Band -width related to filter design. (5 marks)

1 (b) Compare Microstriplines with striplines. (5 marks)

1 (c) Explain Simplified Eber's-moll model, for forward active mode of transister. (5 marks)

1 (d) Draw equivalent circuit representation of two wire transmission line. Explain primary and secondary parameters for the same. (5 marks)

2 (a) Explain Richards transformation and kurodas Identity. How they are used in realization of RF Filter? (10 marks)

2 (b) Explain the role of scattering parameter and its's properties at RF and microwaves. (10 marks)

3 (a) Derive power consideration for transmission line when.
(i) Load Impedance Z_L & source Impedance Z_S are mathched.
(ii) Z_L is matched and Z_S is mismatched. (10 marks)

3 (b) A transmission line of characteristics Impedance Z₀=50 Ω and d=0.15 λ is terminated with a load impedance of Z_L=(25-j 30) Ω.
Find reflection coefficient, input impedance at distance 'd' and VSWR by using Z-smith chart. (10 marks)

4 (a) Explain in brief the principle operation of HEMT and MESFET along with their construction. (10 marks)

4 (b) Find the attenuation of 4 element, 2.5 dB ripple, low pass chebyschew filter at $$ \dfrac {W}{W_C}=2.5 $$ (10 marks)

5 (a) Explain different types of diode model's (RF) and differentiate them with respect to junction capacitance, band gap energy and conductance. (10 marks)

5 (b) Explain what is skin depth? Calculate the skin depth for copper and aliminium at 1GHz and 10 GHz and Find the resistance of 10cm wire with diameter of 1mm
$$ 6_{CU}=64.516 \times 10^6 s/m, 6_{Al}=40 \times 10^6 s/m. $$ (10 marks)

6 (a) Derive expression for internal, external and loaded quality factors for standard series and parallel resonant circuit. (10 marks)

6 (b) For a transmission line circuit involving source and load terminations of Z_G=60 Ω and Z_L=50 Ω respectively and Z₀=75 &Omgea;. Compute the input power and power delivered to load. Assume length of line to be [ dfrac {lambda}{4} ] with source of V_G=8V (10 marks)

Write short note on :-

7 (a) Schottky contacts(7 marks)

7 (b) Equivalent circuit of Resistor's, Inductor and capacitor(7 marks)

7 (c) ABCD parameter(6 marks)